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Belviq (Lorcaserin) Side Effects & Adverse Reactions (List)

Belviq (Lorcaserin) is an anorectic medication manufactured by Arena Pharmaceuticals for the long-term management of obesity.  As of 2012, the FDA approved lorcaserin to promote weight loss in adults with: BMIs exceeding 30 or BMIs exceeding 27 plus [at least] one weight-related medical comorbidity such as diabetes, hyperlipidemia, and/or hypertension.  Upon administration, lorcaserin functions primarily by fully agonizing 5-HT2C receptor sites throughout the central nervous system (CNS).

The full agonism of lorcaserin exerted upon 5-HT2C receptors is understood to suppress appetite, resulting in decreased caloric intake and a corresponding negative energy balance in which weight loss occurs without increased energy expenditure nor fat oxidation.  Some theorize specifically that agonism of 5-HT2C receptors located in the hypothalamus is an especially important weight loss mechanism.  Hypothalamic 5-HT2C receptor agonism is known to upregulate production of proopiomelanocortin (POMC), which in turn normalizes melanocortin signaling to facilitate satiety.

To a lesser extent, lorcaserin is a full agonist at 5-HT2B receptors and partial agonist at 5-HT2A receptors – each of which may contribute modestly to its weight loss effect.  Although many individuals taking Belviq (lorcaserin) end up losing a significant amount of weight during treatment, some may struggle with drug-related side effects and/or adverse reactions.  In the event that you experience side effects from Belviq (lorcaserin), you may find it difficult to justify continuing treatment.

Belviq (Lorcaserin) Side Effects & Adverse Reactions (List)

If you’ve been taking Belviq or are about to initiate treatment, it is important to be cognizant of potential side effects and/or adverse reactions that may occur.  Realize that the side effects you experience while taking lorcaserin may differ significantly from those of another user.  In other words, you may end up experiencing dizziness and fatigue, whereas another individual may end up vomiting.

That said, due to the pharmacodynamic action of lorcaserin, some side effects occur with greater frequency in a general population compared to others.  Some of the most commonly reported Belviq side effects include: constipation, dizziness, dry mouth, fatigue, headache, nausea, and upper respiratory tract infection.  Included below is a more comprehensive list of side effects and adverse reactions that you may experience while taking Belviq (lorcaserin).

Agitation: It is certainly possible for individuals to become more agitated than usual while taking Belviq.  Studies show that administration of a 5-HT2C receptor agonist to animal models increases anxiety, as well as agitation.  Agitation is considered an increase in nervous energy throughout the body, perhaps effectively described as a churning sensation within the stomach.

As a result of increased agitation, you may find yourself feeling restless, distracted, and/or irritable.  To cope with the agitation, it may be helpful to increase physical activity throughout the day [to burn some extra energy], engage in relaxation exercises [to increase parasympathetic nervous system function], as well as to maintain a sleep regimen [to ensure that you’re getting enough sleep].  If the agitation becomes unbearable, you may want to ask your doctor about reducing your dosage and/or utilizing an adjunct anxiolytic to attenuate the agitation.

Allergic reaction: A very small, yet unlucky subset of patients will end up with an allergic reaction to Belviq.  Very serious allergic reactions to this drug are uncommon, however, they can occur.  Signs of a possible allergy to the medication include: confusion, difficulty breathing, dizziness, itchiness, shortness of breath, skin rash, and/or swelling (of your face, lips, tongue, throat).

If you suspect that you’re allergic to Belviq, emergency medical services are necessary – do not hesitate to contact a medical doctor.  Anyone allergic to Belviq will need to discontinue treatment and discuss alternative options with their doctor.  Even if you are allergic to Belviq, chances are favorable that you’ll find a treatment that you can safely tolerate.

Anxiety: A small percentage of individuals taking Belviq may experience anxiety as a side effect.  It is understood that the drug modulates the neurotransmission of serotonin by agonizing 5-HT2C receptors.  Although 5-HT2C agonism helps with weight loss, and may even yield anxiolytic effects in a subset of users – others will become anxious.

It is suspected that anyone with a neuropsychiatric disorder, especially an anxiety disorder would be at increased risk for experiencing Belviq-induced anxiety.  Keep in mind that some anxiety may occur within the first few weeks of treatment and subside as your neurochemistry adapts to the effects of the drug.  Nonetheless, if the anxiety impairs your ability to function in social relationships and/or at work – you should report it to your doctor.

Blurred vision: If you experience blurred vision while taking Belviq, you aren’t alone – others have reported this reaction.  The blurred vision may be accompanied by pupil dilation and/or contraction, as well as seeing “floaters” or weird shapes floating in your peripheral.  Blurred vision is reported as a side effect of nearly every drug that modulates neurochemistry, but is usually not significant enough to be bothersome.

In the case of Belviq, the drug probably isn’t damaging their eyes, however, it may be altering activity in certain areas of the brain such as the visual cortex, leading to perceived abnormalities in visual perception.  To be sure that your eyes are healthy and that no damage has been inflicted from the drug, consult an ophthalmologist for evaluation.  Assuming blurred vision was related to neuromodulation from Belviq, discontinuation should lead to normalization of vision.

Brain fog: Any drug that modifies endogenous neurotransmission has potential to interfere with perception and clarity of thinking.  Unsurprisingly, some individuals using Belviq have reported experiencing “brain fog” or inability to think clearly as a side effect.  This brain fog may be frustrating in that it causes you to feel spaced out, unfocused, and lackadaisical – almost as if you’re stuck in some sort of twilight zone.

In some cases, brain fog will be transient in that it diminishes after a few weeks of treatment as your brain fully adapts to the effects of Belviq.  On the other hand, the brain fog could worsen with time and impair your ability to perform cognitively-demanding tasks.  Even if you end up losing some weight during treatment, sacrificing mental clarity may be an unfavorable tradeoff.

Cardiac complications: Anyone with a history of cardiac events and/or at-risk for cardiac conditions should avoid taking Belviq.  Though there isn’t definitive proof that using Belviq causes any heart conditions, the FDA is closely monitoring patients for any sign of adverse events.  Since Belviq hasn’t been on the market for a long-term, it is unknown as to whether patients may develop serious cardiac complications.

That said, Belviq exhibits a similar mechanism of action to older drugs such as fenfluramine that were eventually banned from sale due to damaging the heart valves.  The high selectivity of Belviq for the 5-HT2C receptor is thought to minimize some of the cardiac risk, but it is possible that some may endure cardiac events from Belviq, especially over a long-term.  What’s more, Belviq exerts an agonist effect upon the 5-HT2B receptor, possibly causing mitral valve regurgitation.

Mitral valve regurgitation occurs when the mitral valve of the heart is unable to fully close, causing a reversal of blood flow and symptoms such as: murmurs, shortness of breath, rapid heartbeat, etc.  If you suspect that Belviq is affecting your heart it is wise to seek comprehensive evaluation from a cardiologist.  Moreover, anyone that’s been using Belviq for an extended duration should receive regular check-ups to ensure healthy heart function.

Chills: A frequently-reported side effect by Belviq users is the occurrence of “chills” throughout the body.  If you feel abnormally chilled during treatment, you’ll want to evaluate whether it may be related to and/or a byproduct of either: hyperthermia (increased body temperature) and/or hyperhidrosis (excessive sweating).  Stimulation of the 5-HT2C receptor in animal models has been shown to increase body temperature, and it just so happens that Belviq targets this receptor, perhaps leading some individuals to develop a fever plus chills.

The chills and/or shivers are triggered upon signaling from the brain to musculature, usually in effort to restore homeostatic body temperature.  Even if a fever doesn’t explain your chills, sweating more than usual (another possible side effect) could lead you to feel chilled – especially if there’s a sudden decrease in ambient temperature and/or wind chill that comes into contact with your sweat.  The chills may also be related to drug-induced modulation of activity within the hypothalamus (via melanocortin receptors), a center of the brain implicated in thermoregulation.

Other possibilities of chills include: allergic reactions, interactions, hormonal changes, and/or prolonged bouts of fasting.  Discuss the chilled feelings with your doctor and determine whether an over-the-counter (OTC) medication or tweak in dosing may help.  Fortunately, most will find the chills to be tolerable and easy to manage by taking a warm shower, consuming a bit more food, and/or wearing extra layers of clothing.

Cognitive deficits: It is estimated that between 1% and 10% of Belviq users experience cognitive deficits during treatment, primarily in the form of impaired attention and/or memory retrieval.  Decline in cognitive performance while taking Belviq may be especially problematic for individuals required to regularly perform cognitively-demanding tasks such as in academic or occupational settings.  It should be mentioned that some individuals report cognitive deficits to be severe within the first few weeks of treatment, but subside over a longer-term.

Others may find that cognitive deficits can be attenuated by dosage adjustments and/or administration of certain adjunct medications and/or supplements.  In the event that cognitive deficits resulting from Belviq lead to poorer academic performance, occupational productivity, and/or quality of life – it may be necessary to discontinue the drug.  Always report cognitive impairment to your doctor as soon as it is noticed.

Confusion: Less than 1% of Belviq users will report severe confusion as a side effect of treatment.  Confusion may be the sign of a serious adverse reaction (e.g. medication allergy) or an interaction with another medication such as another serotonergic agent (causing serotonin syndrome, or abnormally high serotonin).  It is also possible that confusion stems from a significant reduction in catecholaminergic transmission associated with 5-HT2C agonism.

Lack of catecholaminergic signaling leads to cognitive deficits, but may also provoke simultaneous disorientation and/or dissociation.  Sometimes confusion will clear up spontaneously as the brain rewires itself in reaction to the ongoing administration of Belviq, but in other cases, confusion may be unavoidable.  If you happen to be in the minority of individuals who become extremely confused while taking Belviq, do not hesitate to explain your confusion to a medical professional – you may need to discontinue treatment or modify the dosing.

Constipation: Among the most common Belviq side effects, reported to occur in up to 10% of users, is constipation.  The constipation that occurs during treatment with Belviq may stem from alterations in serotonergic transmission.  Altered serotonergic transmission can affect intestinal motility and prolong the shuttling of food through the gastrointestinal tract, leading to infrequent bowel movements and constipation.

The constipation may be more likely to occur in the early stages of treatment and subside after you’ve been taking Belviq for awhile.  If the constipation doesn’t diminish with continued treatment and/or makes you feel bloated, you may be able to reverse it by simply ramping up intake of dietary fiber and drinking more water.  Moreover, if the constipation is unbearable, ask your doctor whether an adjunctive laxative may help normalize bowel movements.

Depression: An uncommon, yet reported side effect of Belviq is depression or low mood.  The reason some individuals likely become depressed during treatment is related to the fact that Belviq stimulates serotonin receptor sites (e.g. 5-HT2C), thereby modifying serotonergic transmission.  Serotonin is a monoamine implicated in maintenance of well-being and positive mood, however, drug-induced modifications of serotonergic transmission can prompt unexpected depression.

It is suspected that individuals diagnosed with major depression or another neuropsychiatric may be most at risk for Belviq-induced depression.  In extreme cases, depression as a side effect may lead to suicidal ideation and/or wanting to die.  If you become increasingly depressed while taking Belviq, it is imperative that this side effect is reported to a medical professional.

Diarrhea:  A disconcerting side effect reported by some Belviq users is diarrhea – characterized by frequent discharge of loose, watery stools.  Diarrhea is suspected to occur as a result of the Belviq irritating the lining of the gastrointestinal tract, but may also occur from drug-related modulation of serotonergic transmission.  Altered serotonergic signaling in the central nervous system can affect intestinal motility, possibly expediting movement of food through the gastrointestinal tract.

There are numerous other reasons that diarrhea may occur while taking Belviq including: insufficient hydration, excessive fiber intake, and/or administering the drug on an empty stomach.  To cope with the diarrhea, some users have found it helpful to increase water intake and electrolytes, reduce dietary fiber, and only take Belviq with food or on a full stomach.  Others have reported that administration of an over-the-counter antidiarrheal adjunct (e.g. Imodium) is helpful.

Keep in mind that while diarrhea may yield additional weight loss, this is not the mechanism by which Belviq is intended to function.  Ongoing diarrhea is unhealthy in that it depletes the body of micronutrients and is often a sign that the body is unable to tolerate the drug.  A subset of patients will find that diarrhea is most prevalent during the first few weeks of treatment and subsides thereafter.  That said, anyone experiencing diarrhea should immediately report it to a medical professional for advice regarding how to correct it.

Difficulty breathing: Another side effect associated with Belviq is difficulty breathing and/or shortness of breath.  Many users have reported that the difficulty in breathing is mild and not overly debilitating.  Any difficulty in breathing could be a sign of an allergic reaction, changes in cardiac function, or hypertension.

Difficulty breathing may also be related to drug-induced changes in sympathetic/parasympathetic tone in response to medication administration.  That said, in the event that you experience difficulty breathing, even if mild, it is important to notify your doctor of this reaction.  It may be necessary to discontinue treatment and/or opt for another drug that doesn’t interfere with your breathing.

Dissociation: Another freaky rare side effect of Belviq is dissociation or feeling as though you are somehow disconnected from your normal self.  Dissociation is difficult to describe, but those that experience it will report feeling totally different than their pre-Belviq selves.  Some cases of dissociation may be transient and subside as users adapt to modulation in neurochemistry as induced by Belviq, however, others may find that dissociation worsens over time.

If you feel as if a robot has taken over your brain and/or body, feel disconnected from human emotion or your thoughts, report this side effect to your doctor.  People can have unpredictable, weird reactions to neuromodulators such as Belviq.  Fortunately, 99% of users won’t end up with this side effect, but for the 1% that experience dissociation – alternative pharmaceuticals may be necessary.

Dizziness: An extremely common side effect reported by up to 10% of Belviq users is dizziness.  Although many individuals will find the dizziness to be of mild or moderate severity, others will report extreme dizziness to the extent that they struggle to maintain balance or feel as if their head is spinning.  Mild or moderate bouts of dizziness as a side effect may be transient and occur as a result of Belviq modifying serotonergic neurotransmission.

As the user’s neurochemistry adapts to the ongoing administration of Belviq over a duration of several weeks, the dizziness may subside.  One theory is that significant upregulation in serotonergic receptor activation within a region of the brain known as the vestibular nuclear complex (VNC) may cause the dizziness.  In extreme cases, dizziness may be related to an interaction of Belviq and another substance, or possibly associated with a medical contraindication.

Certain individuals have noted that lying down with eyes closed helps them cope with the drug-induced dizzy sensation.  Others have suggested that the dizziness is often accompanied by nausea and can be offset upon administration of an over-the-counter antiemetic.  If you feel extremely dizzy, do not hesitate to report it to your doctor – and furthermore, avoid operating motor vehicles or heavy machinery – as the dizziness may affect your fine motor skills.

Dry mouth: Do not be surprised if while taking Belviq you end up with dry mouth (xerostomia).  The exact mechanism by which Belviq may induce dry mouth in a subset of patients remains unclear, but some speculate that its effect within the CNS interferes with saliva production and/or secretion from salivary glands.  Some research of serotonergically-acting agents has shown that they appear to reduce stimulated saliva flow rate mediated via the parotid glands.

Regardless of why dry mouth occurs as a side effect, some individuals will find that the dryness improves after a few weeks of treatment and/or that it becomes easier to cope with.  Improvements in dry mouth may be related to normalization of stimulated saliva flow rate upon CNS adaptation to Belviq.  Still, not only is dry mouth uncomfortable for patients, it could lead to halitosis and expedited tooth decay (resulting from proliferation of pathogenic oral bacteria).

Those that experience dry mouth should receive regular evaluation from a dental professional every 6 months.  To cope with dry mouth, it may be helpful to: chew sugar-free gum, sip water or tea throughout the day, decrease stress, as well as consider a safe over-the-counter saliva substitute.  For the ~10% of users that experience dry mouth as a side effect, it is usually not severe enough to justify discontinuation of the medication.

Erectile changes: In men, Belviq could cause the adverse effect of painful and/or prolonged erections, possibly lasting in excess of 4 hours.  Anyone that experiences a painful and/or protracted erection should stop using the drug and get immediate medical help – as permanent adverse complications could result.  While most will not experience excessively long or painful erections, some may notice that they get more frequent erections or are more interested in sex.

Studies in which 5-HT2C receptor agonists (like Belviq) are administered to rats have documented pro-erectile and pro-ejaculatory effects.  Therefore, it should be expected that a subset of male users may notice an increase in sexual performance while taking Belviq.  That said, not all male users will experience noticeable changes in erectile function.

Euphoria: Less than 1% of Belviq users may end up experiencing euphoria (happiness and excitement).  Should you respond to Belviq with a euphoric mood, it could be the result of an underlying neuropsychiatric condition (e.g. bipolar disorder) or perhaps an interaction effect associated with Belviq and another substance you’re using.  Though the euphoria you’re experiencing may be pleasurable, it could lead to impulsive spending, sexual promiscuity, and/or other unhealthy behaviors.

Furthermore, euphoria is often unsustainable and may be followed by a severe “crash” or low mood.  In some cases, the side effect of euphoria may be indicative of the fact that an individual administering too high of a dose for their neurochemistry to tolerate.  For this reason, a decrease in Belviq dosing may be helpful for reducing euphoria, however, if the euphoria doesn’t subside – it may be necessary to transition to another medication (devoid of 5-HT2C agonism).

Fatigue:  Since most people associate weight loss with increased energy, the side effect of fatigue (reported in 1% to 10% of users) may be counterintuitive.  Unlike some weight loss drugs, Belviq is not understood to dramatically ramp up activation of the sympathetic nervous system through enhancement of catecholamine (e.g. norepinephrine and dopamine) production.  Instead, it agonizes serotonin receptors (5-HT2C) to simultaneously decrease appetite and increase satiety.

This enhancement of serotonin receptor signaling can exert a calming effect, but if taken to an extreme, may lead a person to feel exhausted or unnecessarily fatigued.  Perhaps most problematic is that fatigue may detrimentally affect your ability to engage in physical exercise, sustain productivity at work, and/or drum up the motivation to accomplish tasks around the house.  In some cases, the side effect of fatigue will diminish after several weeks once a person fully adjusts to the full scope of neurochemical changes induced by Belviq.

In other cases, fatigue may result from excessive serotonergic signaling associated with administering too large of a dose.  For this reason, certain individuals may benefit from working with their doctor to reduce their Belviq dosage.  Moreover, medical professionals may be able to prescribe a safe adjunctive agent to combat extreme bouts of fatigue.

Fever: A rare adverse reaction that affects a small percentage of Belviq users is fever.  Some individuals will notice a mild to moderate elevation in body temperature upon initiation of treatment.  The fever may be accompanied by a host of other side effects including: shivering, sweating, chills, and in extreme cases, possibly nausea, vomiting and/or diarrhea.

If the fever is high enough, you may suspect that you’ve contracted a pathogenic virus such as influenza – hence the reason some may report feeling “flu-like” while taking Belviq.  Fevers could be a sign of an allergic reaction to Belviq or a serious interaction from any concurrently administered substances.  Mild cases of hyperthermia may also result from Belviq-induced modulation of serotonergic neurotransmission, specifically by agonizing 5-HT2C receptors.

Studies in animal models have found that injections with 5-HT2C agonists into the brain can generate a hyperthermic response.  In the event that you develop a fever while taking Belviq, it should be immediately reported to a medical doctor.  For some individuals, high fever may be a sign to discontinue treatment, whereas others may report a transient fever that subsides as the body adapts to ongoing drug administration.

Headaches: The single most common side effect of Belviq, reported in up to 17% of users is headaches.  The headaches are thought result directly from Belviq’s agonism of 5-HT2C serotonin receptors.  Studies have shown that agonism of 5-HT2C receptors can alter the diameter of intracranial blood vessels, thereby affecting cerebral blood flow and provoking headaches.

In animal model studies, low doses of the 5-HT2C receptor agonist m-CPP (an agent similar to Belviq) appears to facilitate vasodilation, whereas high doses facilitate vasoconstriction.  Knowing this information, it is possible that similar effects occur in humans such as that low doses of Belviq promote vasodilation for migraine-like headaches, whereas higher doses promote vasoconstriction for tension-type headaches.  Those with a history of migraine and/or conventional headache may experience symptomatic worsening while taking Belviq.

Managing headaches as a side effect of Belviq may involve tweaking the dosing, increasing water intake (to stay hydrated), and/or administering a safe over-the-counter (OTC) headache relief drug.  Though mild headaches may be tolerable, if your headaches are severe, they may significantly impair your quality of life.  Debilitating headaches should be reported to your doctor and all possible reduction strategies should be discussed.

Hot flashes: An uncommon side effect that some users will experience during Belviq treatment is mild hot flashes.  Hot flashes are characterized by sudden, unexpected feelings of feverish heat that are sometimes accompanied by facial flushing and/or sweats.  It is known that serotonergic neurotransmission can affect the occurrence of hot flashes, and since Belviq agonizes 5-HT2C receptors to alter serotonin signaling, this mechanism may be to blame.

Furthermore, the anorectic effect of Belviq may be mediated through action upon the hypothalamus, a region of the brain implicated in thermoregulation.  Modulation of hypothalamic activity may alter thermoregulation, thereby triggering hot flashes.  It is also possible that concentrations of certain hormones change in response to administration of Belviq and/or reduction in food intake, and that as a result of these changes, hot flashes ensue.

Hypertension: It is estimated that between 1% and 10% of Belviq users experience hypertension as a side effect.  In the event that hypertension is left unnoticed, it may lead to more serious health complications such as myocardial infarction and/or transient ischemic attack.  Evidence from animal models suggests that administration of centrally-acting 5-HT2C agonists induce hypertension accompanied by accelerated heart rate.

The fact that Belviq could induce hypertension means that all users should regularly monitor their blood pressure to ensure that it stays within a healthy range.  If you develop hypertension while taking Belviq, you’ll want to talk to your doctor about dosage modifications and/or adjunct antihypertensive interventions.  Thankfully many people end up with lower blood pressure (rather than higher) as a result of their weight loss.

Hypoglycemia: Among diabetics, hypoglycemia is an extremely common side effect of Belviq, affecting up to 29.3% of patients. What’s more, up to 10% of non-diabetic users may find that Belviq causes blood sugar concentrations to plummet.  For this reason, anyone using Belviq should inform friends and/or family to recognize the onset and signs of low blood sugar, as well as ways in they can help reverse drug-related hypoglycemia (e.g. glucose tablets).

Diabetics should pay extra close attention to blood sugar levels during treatment and take proactive steps to avoid hypoglycemic states.  Individuals using medications to treat type 2 diabetes should understand that any weight loss occurring during treatment may exacerbate drops in blood pressure.  If you experience hypoglycemia, contact your doctor and realize that he/she may need to adjust the dosage of your Belviq, and diabetes medications.

Insomnia: During treatment with Belviq, 1% to 10% of users will experience insomnia as a side effect.  The insomnia is characterized by an inability to fall asleep and/or stay asleep throughout the night.  What’s unfortunate about insomnia is that it may lead to additional complications such as anxiety, cognitive impairment, depression, and irritability – as a result of lack of total sleep and/or poor sleep quality.

There are a multitude of reasons insomnia may occur as a side effect of Belviq including: modulation of neurotransmission, insufficient caloric intake (and micronutrient deficiencies) resulting from anorectic effects, and/or disruption of the circadian rhythm.  If the insomnia leads to sleep deprivation and/or excessive daytime sleepiness, it is important to consult a medical professional.  A medical professional may recommend adjusting your dosage and/or administering an adjunct sleep aid to attenuate insomnia.

Irregular heartbeat: All patients taking Belviq should be aware of possible irregular heartbeat as a side effect of treatment.  While irregular heartbeat isn’t always problematic, it may be a sign that a person is at increased risk for a serious cardiac event such as myocardial infarction.  For this reason, if you notice an abnormally rapid, slow, or uneven heartbeat while taking Belviq – it is imperative to inform your doctor as soon as possible.

In some cases, perceived heartbeat irregularities may be nothing more than benign palpitations resulting from increases in anxiety.  However, anyone concerned about the possible toll that Belviq is taking on their heart should consult a cardiologist for a full cardiac evaluation.  Older weight loss drugs such as fenfluramine that functioned by agonizing serotonin receptors were understood to speed up heart rate as a result of vasoconstriction associated with sympathomimetic effects.

Although Belviq is more selective for 5-HT2C receptors than fenfluramine, it still affects the 5-HT2B receptor which could lead to mitral regurgitation.  Mitral regurgitation is associated with an abnormally rapid and/or fluttering heart and caused by a backflow of blood from inability of the mitral valve to close.  Moreover, it is possible that serotonergic agonism could alter blood pressure (and peripheral blood vessel size), whereby blood flow to/from the heart is altered and heartbeat becomes irregular.

Lightheadedness: Some individuals will report lightheadedness as a side effect of Belviq, possibly accompanied by dizziness and fatigue.  In many cases, lightheadedness is only bothersome during the initial few weeks of treatment and diminishes a person’s neurochemistry adjusts to drug-induced serotonergic modulation.  That said, there are numerous other potential causes of lightheadedness (as a side effect of Belviq) including: blood pressure changes, caloric restriction, cardiac function, and medication interactions.

If blood pressure drops too low, such as can occur during weight loss, this could lead you to feel lightheaded.  Lightheadedness may also be a sign that Belviq is detrimentally affecting heart function [as a result of its 5-HT receptor agonism], especially if the lightheadedness is accompanied by other cardiac abnormalities.  You may also want to consider that lightheadedness could stem from an interaction effect and/or contraindication.

What’s more, excessive caloric restriction and/or prolonged bouts of fasting (resulting from appetite suppression) may lead an individual to lose weight too rapidly, and as a result he/she becomes lightheaded.  If Belviq is suppressing your appetite to an extreme and you end up losing weight too quickly, this may be reason as to why you feel lightheaded.  Anyone with lightheadedness should consult a medical professional to rule out cardiac abnormalities and/or hypotension.

Memory impairment: Some individuals will experience significant memory impairment as a side effect of Belviq.  The memory impairment may be characterized as an inability to form new memories and/or difficulty with the retrieval of already-stored memories.  This may affect a person’s ability to perform in a cognitively-demanding academic or occupational field in which optimal memory function is necessary.

Any memory deficits that occur throughout treatment may result from drug-related alterations in neurochemistry, as well as neural activation.  Belviq acts directly upon the 5-HT2C receptors which inhibits catecholamine release in various regions of the brain.  Inhibition of norepinephrine and dopamine release is understood to impair learning and long-term memory formation, likely explaining why some users report memory dysfunction while medicated.

It also is possible that memory deficits are caused by other side effects of Belviq such as anxiety, fatigue, and/or insomnia.  Excessive anxiety, ongoing fatigue, and unmanaged insomnia can all take a toll on memory processes.  If you’re frustrated with inability to form and/or retrieve memories while taking Belviq, talk to your doctor about whether modifying your dosage and/or using an adjunct could be helpful.

Mood changes: You may notice that your mood has changed as a result of using Belviq for weight loss.  Although Belviq helps you lose weight by reducing your appetite, its pharmacodynamics involve targeting 5-HT2C serotonin receptors.  The stimulation of 5-HT2C receptors could cause feelings of anger, agitation, anxiety, depression, or even euphoria.

Substantial changes in mood may be more common among those taking Belviq at extremely high doses and/or among individuals with preexisting neuropsychiatric disorders.  Not everyone’s mood will respond favorably to the modulation in serotonergic transmission, as well as the downstream reduction in catecholamine release (in some regions of the brain).  Communicate any unexpected and/or unwanted mood changes to your doctor as soon as they are noticed.

Muscle aches: A common side effect, experienced by up to 12% of users, is muscle aches and/or pains.  These muscle aches may be confined to a particular region or widespread throughout multiple regions – and accompanied by weakness and/or fatigue.  Evidence suggests that the most common site for muscle aches and/or soreness to occur as a result of Belviq is throughout the back.

If you happen to be one of the unlucky few who experiences muscle aches and/or pain as a side effect, you should report it to your doctor.  Although the soreness may subside with continued medication usage, your doctor may be able to recommend a safe over-the-counter (OTC) adjunct to help alleviate the pain.  Moreover, you may want to consider taking a hot bath and/or gently massaging the areas in the most pain.

Nausea: A fairly common side effect experienced in up to 10% of users is nausea.  The nausea may be most severe during the first few days or weeks of treatment, but subside thereafter as your neurobiology adapts to the drug.  For some individuals, nausea is accompanied by gastrointestinal distress, dizziness, and in extreme cases – leads to vomiting.

If you feel nauseated all day as a result of Belviq, ask your doctor and/or pharmacist whether anything can be done to reduce the intensity.  Certain individuals may realize that their nausea can be attenuated with administration of an adjunct antiemetic.  Others may benefit from a reduction in Belviq dosing or by administering the drug with a large meal (as opposed to on an empty stomach).

Prolactin increases: Administration of Belviq is known to increase concentrations of prolactin in over 6% of users, likely as a result of 5-HT2C receptor stimulation.  Research suggests that enhanced stimulation of 5-HT2C receptor sites could cause hyperprolactinemia or abnormally high prolactin levels in the bloodstream.  Those with drug-induced hyperprolactinemia may experience symptoms such as gynecomastia (breast enlargement), galactorrhea (milk secretion from the breasts), and reduced libido.

Symptoms suggestive of hyperprolactinemia (e.g. gynecomastia and galactorrhea) should be reported to a medical professional immediately and prolactin levels should be measured.  If your prolactin levels are higher-than-average from taking Belviq, your doctor may need to reduce your dosage and/or help you transition to another medication.

Pulmonary hypertension: It is possible that some users may eventually report onset of pulmonary hypertension (PAH) as an adverse reaction to Belviq.  Pulmonary hypertension is a serious medical condition in which pulmonary arterial pressure exceeds 25 mg Hg at rest or 30 mm Hg during activity.  Signs of pulmonary hypertension include shortness of breath, fatigue, and fainting.

Though no cases of pulmonary hypertension have been reported among current Belviq users, this may be due to the recency of Belviq approval (2012).  Perhaps in forthcoming years, cases of pulmonary hypertension will emerge as a result of long-term Belviq administration.  Though risks of pulmonary hypertension may be reduced as a result of 5-HT2C selectivity, the full extent of risk remains unknown.  Anyone suspecting potential pulmonary hypertension from Belviq should consult a cardiologist for urgent evaluation.

Restlessness: It is possible that some individuals will exhibit restless behaviors and/or appear unable to sit still while taking Belviq.  Although not all Belviq users are likely to become restless, some may experience restlessness as a direct result of drug-induced anxiety and/or agitation.  The anxious and agitated feelings of nervous energy or “internal stirring” can be triggered by 5-HT2C agonism.

Like most side effects, the severity of restlessness may decrease as your neurochemistry and physiology adapt to the ongoing administration of Belviq.  If the restlessness fails to improve and is impairing your ability to function, it may be useful to regularly engage in relaxation exercises (e.g. deep breathing) to reduce anxiety, as well as increase physical activity in attempt to reduce the restless energy.  Still, if the restlessness is intolerable, it may be reasonable to ask your doctor for a lower dose, an anxiolytic adjunct, and/or to test a different medication.

Sensations:  A minority of Belviq users will report adverse physical sensations such as: burning, heaviness, and/or tingling.  These sensations may be isolated to a particular area of the body such as the chest, or occur in multiple areas simultaneously such as the arms, feet, and hands.  Any abnormal physical sensations may arise from drug-induced modification of CNS activity involving the stimulation of 5-HT2 receptors, and possibly from corresponding changes in PNS activity.

It is well-documented that burning, heaviness, and tingling sensations are common among those administering different classes of serotonin receptor agonists such as triptans.  Although triptans agonize different receptor sites from Belviq, perhaps there’s an overlap in some mechanism that causes abnormal sensations.  Any bizarre or unwanted physical sensations noticed as a side effect should be mentioned to a doctor to ensure that they aren’t a sign of something serious.

Skin rash: Approximately 1% to 10% of individuals will develop a skin rash while using Belviq.  The skin rash may be isolated to a particular region or widespread throughout the entire body.  It may be characterized by redness, hives, and/or itchiness – and detrimentally affect your appearance.

Since any skin rash experienced during treatment could signify a serious allergic reaction to Belviq, it should be urgently reported to a medical doctor.  Although allergic reactions to this medication are uncommon, they may explain the occurrence of the rash.  Other individuals may develop a rash not because they are allergic to Belviq, but because they aren’t consuming enough food and/or specific nutrients during treatment.

If you go for long periods of time without sufficient caloric intake and/or fail to consume nutrient-dense foods, you may end up depriving your body of critical nutrients it needs for maintenance of healthy skin.  As a result, your skin health may decline throughout treatment, resulting in onset of skin rashes.  Those that develop a persistent skin rash may want to get a referral to a dermatologist for a more extensive evaluation.

Sleep disturbances: While a number of Belviq users report insomnia as a side effect, many find that once they’re able to actually fall asleep – that they sleep extremely well.  Others may experience a combination of insomnia, as well as sleep disturbances such as: frequently waking throughout the night, weird and/or vivid dreams, and nightmares.  These sleep disturbances may be more likely to occur in the early stages of treatment as a result of Belviq significantly impacting the neurochemistry of the user.

Sleep disturbances may be caused by Belviq’s modulation of neurochemistry, which in turn affects your brain waves and/or transition through sleep cycles.  If you’re having sleep disturbances during treatment, and wake up in the morning feeling groggy or if your sleep quality was extremely poor, you may want to consult a sleep specialist for an evaluation.  Ideally, you’d want to get a sleep evaluation prior to treatment, as well as upon commencement to pinpoint specific ways by which the drug may be affecting sleep.

The problem with sleep disturbances is that they may affect your sleep quality and/or length.  Suboptimal sleep quality and/or length can lead to other complications such as anxiety, brain fog, and daytime fatigue.  Those that continue to experience sleep disturbances after several weeks of Belviq may need to ask their doctor about dosing modifications or utilization of an adjunct sleep aid.

Stomach aches: A very common side effect of Belviq is upset stomach and/or stomach aches.  There are a multitude of possible reasons users experience stomach aches during treatment including: altered gastrointestinal motility (mediated in part by serotonergic signaling), excessive caloric restriction, and/or gastrointestinal irritation.  Since Belviq may expediting or slowing the movement of food through your intestinal tract, it is reasonable to expect a stomach ache – possibly along with diarrhea or constipation.

The weight loss that occurs during treatment is related to the drug suppressing appetite and increasing satiety, possibly leading to prolonged bouts without caloric intake.  If you were to go for an extended period without food during treatment, you may experience stomach aches in the form of hunger pangs.  Though stomach aches can be a nuisance, they are generally manageable by staying hydrated, modifying diet, and sometimes with over-the-counter medications.

Suicidal thoughts: Estimates suggest that up to 1% of all individuals taking Belviq will experience depression and suicidal thoughts as an adverse reaction.  If you ever become suicidal and/or feel as though you want to die, seek emergency medical care and recognize that you may need to find a different weight loss medication.  Belviq is understood to agonize 5-HT2C serotonin receptors, and this agonism can increase anxiety, depression, and even provoke suicidal thoughts in some users.

The suicidal thoughts may be related to altered neurotransmission of serotonin and reductions in catecholamine concentrations, all mediated by 5-HT2C sites.  Ironically, drugs that function opposite to Belviq by acting as 5-HT2C antagonists tend to improve depressed mood and reduce anxiety, but also may cause weight gain.  Those with a history of neuropsychiatric disorders are thought to be most at risk for suicidal thoughts while taking Belviq due to underlying neurochemical abnormalities and/or sensitivities.

Sweating: A small percentage of individuals (1%) will experience excessive sweating (hyperhidrosis) while taking Belviq.  The sweating may occur during the daytime, resulting in soaked clothes at work – and/or throughout the night, drenching your bed sheets.  Since the drug is understood to act upon serotonergic systems, and serotonin is implicated in thermoregulation – it may be that Belviq slightly alters thermoregulatory processes to provoke sweating.

If the sweating is directly related to changes in thermoregulation, it may be accompanied by unexpected hot flashes and/or chills.  It is also possible that increased sweating is a complication of other Belviq-induced side effects such as anxiety.  Agonism of the 5-HT2C receptors may be anxiogenic for certain individuals, triggering anxiety and a corresponding increase in sweat secretion.

For most individuals, as long as the drug is helping with weight loss, profuse sweating will be perceived as nothing more than a minor annoyance.  To cope with the sweating, it may be helpful to engage in relaxation exercises – as this should help combat the anxiety-induced sweating.  Since excessive sweating may lead to depletion of electrolytes and/or dehydration, it may be necessary to take steps to replenish lost electrolytes and drink extra water.

Swelling: Although uncommon, some individuals will notice that their ankles, feet, and/or hands swell up while taking Belviq.  This is possibly due to peripheral edema, or excessive accumulation of watery fluid within tissue cavities throughout the arms and legs.  The edema may be isolated to just one particular area (e.g. feet), or could occur in multiple areas simultaneously (e.g. hands and ankles).

Most people notice the onset of edema when their arms and/or legs: feel heavier than usual, exhibit a swollen appearance, clothing or jewelry no longer fit properly, and/or areas feel painful.  Although edema may be nothing more than a mild reaction for some users, others may experience severe swelling as a sign of an allergic reaction.  Do not hesitate to inform your doctor of any edema that you notice during treatment.

Tiredness: Users have reported that when taking Belviq, they experience bouts of daytime tiredness.  The side effect of tiredness is probably a direct result of the drug acting as a 5-HT2C receptor agonist.  Research has shown that activating 5-HT2C receptors in animal models decreases their physical activity (suggestive of tiredness), whereas knocking out the 5-HT2C receptors increases activity.

In humans, it appears as though administering a 5-HT2C receptor antagonist (the opposite effect of Belviq) can attenuate perception of fatigue among those with chronic fatigue syndrome (CFS).  Furthermore, since agonizing the 5-HT2C receptor inhibits release of catecholamines in certain regions of the CNS, it may be that reduced catecholaminergic transmission plays a role in the onset of tiredness.  Most evidence indicates that as 5-HT2C receptor agonism increases, so will tiredness.

Since the tiredness may be a dose-dependent side effect, such that higher doses induce more tiredness than lower doses, some users may find that decreasing their dosage helps improve their energy levels.  Others may find that even at the lowest therapeutic dose of Belviq, that tiredness is persistent and fails to subside.  If the tiredness is interfering with your ability to function, you may need to talk to your doctor about using wakefulness enhancers (e.g. caffeine) or testing a different medication.

Tremor: It is estimated that between 1% and 10% of Belviq users will experience tremor or uncontrollable shakes.  It isn’t known exactly why some individuals report tremor as a side effect, but it could be a result of altered serotonergic and/or downstream catecholaminergic transmission.  Some speculate that tremor could be a consequence of other side effects such as anxiety and agitation.

If you become shaky during your course of treatment, ask your doctor about what can be done.  It is possible that you may be taking too much Belviq for your body to handle, and that upon dosage reduction, the tremor abates.  Engaging in relaxation exercises, mild physical activity, and doctor-recommended anxiolytics may also prove useful in combatting the side effect of tremor.

Upper respiratory tract infection: Interestingly, up to 14.8% of patients involved Belviq clinical trials experienced an upper respiratory tract infection, making it one of the more common side effects.  An upper respiratory tract infection presents itself as a myriad of symptoms such as: coughing, nasal pressure, sneezing, sinus pain, runny nose, and/or watery eyes.  If you suddenly feel as though you’ve come down with a sinus infection (i.e. sinusitis) or as if your allergies are flaring up while taking Belviq, what you’re experiencing is likely attributed to the medication.

Many individuals who report upper respiratory tract effects in the early weeks of treatment will notice that they gradually subside with continued administration.  Nevertheless, if your congestion and/or nasal pressure fail to diminish in intensity or are debilitating, this could be a sign that you’re allergic to a chemical constituent of Belviq.  Take steps to manage any treatment-induced upper respiratory tract effects by working with a medical professional.

Vomiting: Although uncommon, one of the most debilitating side effects of Belviq is vomiting. Vomiting may occur as an indirect result of Belviq modifying serotonin signaling and/or irritating the lining of the gastrointestinal (GI) tract.  Gastrointestinal irritation often provokes nausea, which could lead to vomiting.

It is also possible that vomiting is triggered as a result of Belviq crossing the blood-brain-barrier (BBB) and modifying serotonergic activity in the chemoreceptor zone of the brain (positioned within the brainstem).  In many cases, intermittent vomiting may only occur in the early weeks of treatment and diminish once a person’s neurochemistry and biology have adapted to the drug.  Severe and/or incessant vomiting may be a sign of an allergic reaction, an interaction (with another substance) and/or taking too high of a dose.

Any vomiting should be reported to a medical doctor so that serious complications can be ruled out.  Some individuals may avert vomiting by consuming food along with Belviq to reduce GI irritation, whereas others may find that taking the drug on an empty stomach leads to less vomiting.  Moreover, reducing the dose of Belviq and/or administering an antiemetic adjunct may also decrease likelihood of vomiting.

Weakness: Some individuals will experience muscle weakness or report feeling weaker than usual while taking Belviq.  In certain cases, the side effect of weakness may stem directly from fatigue (lower energy level) as triggered by agonism of 5-HT2C receptors.  A reduction in energy may make it more difficult to perform physical tasks, and as a result, weakness ensues.

Agonism of the 5-HT2C receptor is favorable for decreasing appetite, but can also decrease catecholamine release in certain areas of the central nervous system.  Reduced catecholamine release may lead to the fatigue and corresponding weakness.  It is also possible that an individual taking Belviq may engage in less physical activity over an extended duration (as a result of the lower energy level).

While the individual will still lose weight from consuming fewer calories, he/she may also lose lean body mass and muscle strength – each contributing to the weakness.  For a subset of users, the weakness will improve as the body adapts to Belviq over a period of weeks or months.  In other cases, individuals may need to work with a doctor to decrease dosing and/or use an adjunct to increase energy levels (in hopes that weakness improves).

Weight gain: Contrary to expectations of weight loss, a small number of individuals will report experiencing weight gain as a side effect of Belviq.  Any weight gain reported will be most likely to occur in the early weeks of treatment and is unlikely to be significant.  In the first few weeks of Belviq treatment, some may gain weight from increases in water weight or due to the fact that the drug hasn’t fully taken effect.

Others may end up gaining weight because they are taking too low of a dose.  If a medical professional revises the dosing of Belviq and titrates it upwards to reach a therapeutic level, the weight gain should transform into “weight loss.”  Assuming you’ve been packing on weight with Belviq and are taking the proper dose, you may need your doctor to rule out other medical conditions (e.g. hypothyroidism) that could interfere with your weight loss efforts.

Furthermore, if weight gain occurs, your doctor should assess whether other medications or supplements that you’re administering with Belviq may interfere with its pharmacokinetics or offset its 5-HT2C agonism.  It is plausible that weight gain may occur in some users that have been on Belviq for an extremely long-term (e.g. years) as a result of developing tolerance to its weight loss effect.  If tolerance is the culprit for weight gain, your doctor may need to assess whether it’s necessary to increase the dosing and/or consider other interventions.

Note: In the event that you experience any side effects and/or adverse reactions, or have a question about Belviq (Lorcaserin) – it is important to immediately contact a medical professional for proper guidance.  A medical professional is trained to recognize severe adverse reactions, answer medical questions, as well as address other treatment-related complications.  If you’ve experienced a side effect that wasn’t listed above, be sure to share it in the comments section below.

Variables that influence Belviq side effects

There are several variables that will likely influence the specific side effects, severity of side effects, and number of total side effects – that you experience while taking Belviq.  These influential variables include: Belviq dosage, co-administered substances, term of administration, CYP450 metabolism, and other individual factors (e.g. food intake, genetics, medical conditions, physical activity, etc.).  Whenever attempting to understand the side effects that you’re experiencing, it may help to reflect upon these variables.

  1. Dosage (10 mg, b.i.d.)

The clinically recommended dosage of Belviq for the induction of weight loss is 10 mg, twice per day (b.i.d.).  As of current, there’s no clinical evidence to suggest that lower doses nor higher doses than 20 mg (b.i.d.) effectively or safely promote weight loss.  For this reason, it should be assumed that all patients are following clinically recommended Belviq administration guidelines.

That said, a subset of individuals may end up taking supratherapeutic or subtherapeutic doses – for various reasons.  Research suggests that the effect of Belviq is dose-dependent in that higher doses elicit a more substantial effect upon the central nervous system than lower doses.  Based on this information, it can be assumed that high doses of Belviq will provoke a greater number of side effects, as well as more severe side effects compared to lower doses.

Individuals that may be using a supratherapeutic dose of Belviq (e.g. exceeding 10 mg, b.i.d.) are at greatest risk for severe side effects and adverse reactions.  At supratherapeutic doses, the lorcaserin is exerting a greater effect upon 5-HT2C receptor sites, and for this reason, any side effects generated by centrally agonizing 5-HT2C receptors will be amplified.  Conversely, subtherapeutic doses (e.g. under 10 mg, b.i.d.) of lorcaserin exert a less significant effect upon 5-HT2C receptor sites and side effects associated with 5-HT2C agonism are dampened.

Side effects may also be of greater severity among high-dose users due to more substantial disruption of homeostatic processes.  As a result of more substantial homeostatic disruption, compensatory endogenous feedback mechanisms are activated more significantly in attempt to restore homeostasis.  For example, suppose someone taking a large dose of lorcaserin experiences an increase in body temperature from the neurochemical modifications induced by the drug.

In attempt to normalize temperature, homeostatic mechanisms kick-in and effects such as “shivering” or chills may occur.  Keep in mind that the temperature shift was just one hypothetical example of a possible side effect associated with homeostatic maintenance.  The homeostatic function of lower dose users won’t be as disrupted as high dose users, and may never reach the threshold responsible for provoking side effects.

It should also be noted that the pharmacokinetic burden of high doses is more significant than that of low doses.  In other words, the efficiency by which the body absorbs, metabolizes, distributes, and excretes lorcaserin is less at high doses – possibly triggering more side effects.  At lower doses, the body has an easier time processing lorcaserin, and as a result, fewer pharmacokinetic-related side effects are likely to occur.  In summary, the larger the dose of Belviq you’re using, the more side effects you should expect.

  1. Co-administered substances

Any co-administered substances you’re taking could either: attenuate Belviq-induced side effects, cause interaction effects, potentiate side effects of Belviq, or have zero influence on the side effects you experience from Belviq.  If you are taking other substances along with Belviq, it is imperative that they are considered safe by a physician.  Co-administered agents can affect Belviq’s pharmacokinetics and/or pharmacodynamic effect, possibly leading to more side effects.

Belviq and its metabolites are subject to metabolism through a host of CYP450 isoenzymatic pathways including: CYP2B6, CYP2D6, CYP1A2, and CYP3A4.  Any drugs that are classified as “inducers” or “inhibitors.”  If you were to take Belviq along with a drug that induces a CYP450 enzymatic pathway by which it is metabolized, it may enter systemic circulation much quicker and with greater potency than expected – leading to rapid onset of serious side effects and/or reactions.

Substances taken with Belviq that inhibit a CYP450 enzymatic pathway will slow its hepatic metabolism, thereby increasing likelihood of side effects and/or adverse reactions.  Those who aren’t co-administering any other substances along with Belviq should metabolize the drug at a normative rate, resulting in fewer side effects.  In addition to pharmacokinetic-related reactions from co-administered substances, other substances may affect its pharmacodynamics.

Any co-administered agent that alters neurochemical processes along with Belviq is likely to increase odds of side effects and/or adverse reactions.  For example, agents that enhance serotonergic signaling (e.g. SSRIs, SNRIs, TCAs, MAOIs, triptans, etc.) could provoke serious reactions such as “serotonin syndrome” if administered concurrently with Belviq.  On the other hand, administration of agents that offset the neurochemical effect of Belviq may decrease its effect upon the CNS, which could lead to fewer therapeutic effects and a correspondingly lower number of side effects.

It is also possible that certain co-administered substances may have zero interaction with the pharmacokinetics nor pharmacodynamics of Belviq, yet still manage to potentiate or attenuate its side effects.  For example, someone using an over-the-counter drug may not never experience certain Belviq side effects such as headache due to the fact that the co-administered substance is combatting the side effects.  On the other hand, someone using a supplement to decrease arousal may find that it potentiates the drowsiness as a side effect of Belviq.

Finally, users may want to also consider that the side effects they’re attributing to Belviq – are really from co-administered substances.  For example, if you started taking a dietary supplement around the same time as Belviq, you may mistakenly assume that what you’re experiencing is solely from the Belviq.  In reality, it could be that the other substances you’re using are the culprit for your side effects.

Note: Before using any other substances (drugs, supplements, etc.) in addition to Belviq, approval from a medical professional is necessary to ensure safety.

  1. Term of Administration

The duration over which you’ve been taking Belviq could influence the number and severity of side effects that you experience.  There’s no universally predictable relationship between the term of administration and side effects.  Some individuals may notice severe side effects early in treatment, whereas others will report the onset of debilitating side effects only after an extended treatment term.  That said, it is understood that the occurrence and/or severities of side effects may differ based upon the specific term over which you’ve used Belviq.

  • Short-term: When initiating treatment with Belviq, a host of side effects are likely to emerge. Many of the side effects experienced over a short-term (e.g. several weeks) are due to the fact that your central nervous system hasn’t had much time to adapt itself to regular Belviq administration.  Furthermore, since Belviq is not recommended to be titrated, users jump from zero drug in their systems to 10 mg (b.i.d.) – possibly surprising the CNS and increasing likelihood of side effects.
  • Moderate-term: Over a moderate term of several months, a user’s central nervous system should’ve adapted itself to expect the twice-daily administration of 10 mg Belviq. As a result of the CNS adaptations, many of the side effects from early in treatment will have diminished and/or subsided.  It is also possible that over a moderate term, users will have learned coping strategies and/or figured out safe adjuncts to minimize severity of side effects – making Belviq more tolerable.
  • Long-term: Anyone that’s used Belviq for a long-term of years likely tolerates the drug fairly well – otherwise they would’ve discontinued after a short or moderate-term of treatment. Over the long-term, Belviq users may continue to refine side effect mitigation strategies such as adjunctive agents and/or lifestyle changes.  That said, it is possible that over a long-term, Belviq may have taken a cumulative toll on a person’s neurochemistry and/or physiology.  This cumulative toll may lead to the unexpected emergence of long-term effects (e.g. cardiac abnormalities).  It is also possible that over a long-term, Belviq stops working and users end up on a supratherapeutic dose to continue the weight loss.  As a result of any dosage increases and/or administration of adjunct potentiators, side effects could become more severe.
  1. Individual factors

Two Belviq users may take the exact same dose of the drug (10 mg, b.i.d.) [without any other substances] for a duration of 3 months, yet report drastically different side effects.  One of these individuals may report debilitating headaches, mild fatigue, and moderate dizziness – whereas the other user may only experience severe constipation.  Since the dosing of Belviq, term of administration, and co-administered substances are the same among these users – side effects should be suspected to be similar.

What explains the differences in side effect occurrence and severity among these two hypothetical users?  Individual factors.  It is likely that individualized factors such as: administration details, age, body size/composition, genetics/epigenetics, and medical conditions – help explain why one person reacts totally different to Belviq or finds it easier to tolerate than another.

  • Administration details: The exact details regarding Belviq administration may affect the occurrence and/or severity of side effects. A person who always administers Belviq with food may experience different side effects than if he/she administered it on an empty stomach.  It is possible that the amount of elapsed time between food consumption and Belviq administration could impact its side effects.  For example, someone who doesn’t eat for 20 hours prior to using Belviq and waits at least 4 hours to eat after its administration – may experience different side effects than if he/she ate 2 hours before and 2 hours after Belviq.  Furthermore, if taken with food, the type of food (carb, fat, protein) may have a subtle effect upon pharmacokinetics, leading to slightly different reactions.  It should also be considered that strict adherence to a strict, evenly-spaced dosing schedule (e.g. 6 AM and 6 PM) may lead to fewer side effects than deviations in dosing (e.g. 5 AM and 9 PM one day, then 7 AM and 11 PM the next).
  • Age of user: It could be hypothesized that age of the Belviq user could influence the side effects that a person experiences. Belviq is approved by the FDA for usage in adults (18+), but it is possible that there are differences in side effects based on whether the user is a young adult vs. elderly.  Elderly adults may exhibit decline in organ function (e.g. liver, kidneys, etc.) which may affect the pharmacokinetics, and ultimately side effects of Belviq.  Furthermore, elderly individuals are often taking other medications for age-related health conditions – possibly interacting with Belviq to increase side effects.  Healthy middle-aged and younger adults should exhibit normative organ function and may have fewer pharmacokinetic-related side effects.  That said, individuals from 18 to mid-20s are still undergoing brain development.  Since these individuals lack fully developed brains, it is possible that the neurochemical alterations induced by Belviq could interfere with optimal development, leading to long-term complications.
  • Body size & composition: A person’s body size and composition (muscle and fat %) may have a slightly influence on side effect occurrence. A man taking Belviq who’s 6’5” and 400 lbs. may experience different side effects than a woman who’s 5’0” and 200 lbs.  The dose of 10 mg (b.i.d.) may be easier to tolerate for the larger man compared to the smaller woman due to the fact that he’s bigger size in respect to the dose administered.  It is also possible that body composition of the user could impact its pharmacokinetics (how Belviq is metabolized), thereby altering side effects.  In other words, your body fat percentage and lean muscle mass may dictate some side effects.
  • Genetics/epigenetics: It is well-understood that a person’s genes could influence the pharmacokinetics of Belviq. Polymorphisms of genes encoding for any hepatic isoenzymes such as CYP2B6, CYP2D6, CYP1A2, and CYP3A4 – could expedite or prolong Belviq metabolism.  Those with normative genetic expression are classified as “extensive metabolizers” and are less likely to experience pharmacokinetic-related side effects.  However, those with a polymorphism indicating underexpression or overexpression of a particular isoenzyme may exhibit: rapid, intermediate, or poor metabolism – leading to unpredictable side effects.  Additionally, variations in genes implicated in neurochemical processes (e.g. serotonin transport) may influence Belviq side effects.  A person’s current epigenetic expression (gene expression as dictated by environment) – may buffer against OR potentiate various side effects of drugs.  You can test for genetic polymorphisms with services like GeneSight.
  • Food intake: The amount of food that is consumed while taking Belviq could have an indirect effect upon drug-related side effects. Though it should be expected that individuals using Belviq will consume fewer calories than prior to treatment, insufficient caloric intake may lead to the occurrence of side effects such as: dizziness, fatigue, and upset stomach – possibly overlapping with those from the drug.  In other words, the effects from suboptimal caloric intake may exacerbate side effects of Belviq.  It should also be considered that diets lacking in nutrient-dense foods may lead to micronutrient deficiencies, also possibly exacerbating drug-induced side effects.
  • Physical activity: It is known that physical activity level can affect brain function, hormone production, and physiology. Someone who is very active during Belviq treatment may experience different side effects than if he/she was sedentary (inactive).  It is possible that someone who goes for a jog each day for 20 minutes feels more energetic and less bogged down with side effects than a person who avoids all forms of exercise.  That said, it is also possible that too much physical activity (e.g. running for 60 minutes per day) could increase odds of adverse reactions (e.g. cardiac events) or exacerbate side effects such as fatigue.
  • Medical conditions: Your doctor should know whether you have a medical condition that is contraindicated with Belviq. Those with a history of cardiac events, neuropsychiatric conditions, or organ dysfunction (e.g. liver/kidney impairment) should avoid using this medication – as it may increase probability of a severe adverse reaction.  Even if you have been diagnosed with another medical condition that isn’t contraindicated with Belviq, it is possible that the drugs used to treat that condition may interact with Belviq – leading to more side effects.  Individuals with medical comorbidities are at greater risk for side effects than those without other medical conditions [in addition to obesity].
  • Stress & Sleep: Side effects of Belviq may be more difficult to deal with among those who are highly stressed and/or those with poor sleep hygiene. High stress may intensify certain side effects of the medication such as anxiety, dizziness, and insomnia – making it more difficult to tolerate than lower stress.  Additionally, suboptimal sleep quality or length could lead to exacerbation of drug-induced side effects.  There’s reason to believe that low stress and quality sleep could act as a buffer against certain side effects.

Belviq (Lorcaserin): Do the benefits outweigh the side effects?

Anyone taking Belviq should understand that it was prescribed to them by a medical professional because it was thought that the potential health benefit would outweigh the side effects.  That said, while using Belviq it is important to evaluate whether the therapeutic weight loss effect outweighs the side effects that you experience.  A subset of lucky individuals will experience the utopian scenario in which weight loss occurs without any unwanted side effects.

For these individuals, it makes sense to continue Belviq treatment for as long as is considered necessary by a medical doctor.  Other Belviq users may be lucky enough to experience no side effects, but may be less lucky in that it doesn’t help them lose much weight.  No matter if you tolerate the drug perfectly well, if it’s therapeutically ineffective for inducing weight loss – it probably doesn’t make much sense to continue treatment.

Opposite to utopian scenario is the dystopian scenario in which debilitating side effects occur without weight loss.  Anyone with debilitating side effects who also doesn’t lose weight from treatment is unlikely to continue Belviq.  That said, even if an individual loses some weight during treatment, any severe side effects may interfere with a person’s quality of life and/or occupational performance – making it smarter to discontinue the medication.

A majority of Belviq users will experience a blend of weight loss and side effects.  In the event that side effects are moderate severity and weight loss is modest, it may make sense to pursue other options.  On the other hand, someone experiencing moderate weight loss and moderate side effects may decide that the side effects are a worthy sacrifice if they can lose some weight.

Always communicate to your doctor whether, in your experience, the benefits and/or upside of Belviq outweigh the drawbacks and/or downside of its administration.  Throughout your treatment, it may help to document subjective effects, side effects and body weight in a journal.  By documenting how well the drug seems to be working, tolerability, and weight changes – you’ll have some evidence to share with your doctor so that he/she can optimize your treatment outcome.

Other things users should know about Belviq (Lorcaserin)…

Some consumers are aware of the fact that lorcaserin was originally submitted for FDA approval in 2009.  An FDA advisory board voted against the approval of lorcaserin in 2010 due to safety concerns, including data from animal studies suggesting that the drug could provoke the growth of cancerous mammary tumors.  Since tumor growth was evident in animal model trials (involving rats), and weight loss derived from lorcaserin was only of marginal significance, the potential risks of lorcaserin administration in humans were hypothesized to outweigh its therapeutic effect.

In reaction to the FDA’s denial of approval in 2010, lorcaserin developers conducted additional follow-up clinical trials and [as of 2012] presented all new data to the FDA.  The newer data was convincing enough for the FDA advisory board that lorcaserin was safe and effective for the induction of weight loss among humans with obesity.  It was reported that the FDA advisory board voted 19-4-1 in favor of lorcaserin approval in June 2012.

Nonetheless, the FDA suggested carefully monitoring patients receiving lorcaserin for potential heart valve issues during treatment.  In May 2013, lorcaserin was classified as a Schedule IV controlled-substance by the U.S. DEA on the basis of its hallucinogenic properties at supratherapeutic doses, possibly leading to drug-induced psychosis.  Results from Phase 2 clinical trials suggested that lorcaserin may increase risk for cardiac valvulopathy, however, Phase 3 results suggested that rates of cardiac valvulopathy among lorcaserin users were only 2.4% – compared to 2% in the control group.

It is thought that selective agonism of the 5-HT2C receptor helps minimize risk of serious cardiac reactions.  To a negligible extent, it affects 5-HT2A receptors (18-fold less than 5-HT2C) and 5-HT2B receptors (104-fold less than 5-HT2C).  Though the effect upon 5-HT2B is negligible, some may still be concerned of possible cardiac complications based on the finding that previously-approved weight loss drugs activating the 5-HT2B receptor damaged heart valves.

All patients taking lorcaserin should receive regular checkups to ensure healthy cardiovascular function. Experts recommend discontinuation of the medication if patients fail to lose at least 5% body weight within the first 12-weeks of administration.  Anyone considering Belviq (lorcaserin) should be fully informed of potential risks prior to initiation of treatment.

Possible ways to reduce Belviq (Lorcaserin) side effects

If you’re struggling to tolerate Belviq, you may want to consider implementing side effect mitigation strategies.  Prior to implementing any of side effect mitigation strategies listed below, it is important to verify safety and hypothesized efficacy with a medical professional.  Keep in mind that the effectiveness of such strategies for mitigation of side effects may be subject to individual variation.  Examples of potentially useful side effect mitigation strategies include: strict adherence to timing of administration and dosing, taking with food vs. on an empty stomach, using a safe adjunct to combat side effects, and reducing the dosage.

  1. Adherence to administration schedule: To reduce likelihood of severe Belviq side effects, a simple strategy involves strictly adhering to administration guidelines as suggested by your doctor. This means taking Belviq at the exact same times every single day – without missing a dose. Most suggest that there should be a 12-hour window between administration of the first and second doses.  This means that users administering Belviq at 7 AM should take their next dose at 7 PM.  Side effects could be caused by irregularities in administration timing such as: 6 AM and 8 PM (possibly too big of a gap) or 6 AM and 2 PM (not enough time between doses).  It is also possible that day-to-day variations in dosing times such as taking Belviq at 8 AM and 8 PM, followed by 5 AM and 5 PM, then 7 AM and 7 PM – may lead to more severe side effects due to the fact that the circadian rhythm cannot reliably adjust itself to the drug.  It may be easier to adhere to a strict dosing schedule if you set a twice-per day alarm on your phone for the exact times at which you are supposed to take Belviq.  Moreover, it may take some experimentation to determine the specific times (e.g. 5 AM/5 PM, 7 AM/7 PM, 9 AM/9 PM) – work best for you.
  2. Testing Food vs. Empty Stomach: If you’re experiencing gastrointestinal-related side effects such as upset stomach, nausea, constipation, or diarrhea – it may be worth testing whether you respond best to taking Belviq with food versus on an empty stomach. It is said that the drug can be safely taken with food or on an empty stomach, but it’s possible that you may respond better to one over the other. If you want to get more detailed, you could consider tracking the type of food (fat, protein, carb) to determine whether side effects are reduced as a result of consuming a particular food type than another.  You could also test whether timing of food consumption before/after Belviq administration increases/decreases side effects.  For example, you may find that eating exactly 2 hours before and 4 hours after Belviq administration reduces certain side effects, whereas eating 10 minutes before and 5 hours after its administration may provoke more side effects.  While experimenting with meal timing before and after administration may not make a difference for everyone, it could help with gastrointestinal side effects.
  3. Eliminate unnecessary substances: Some individuals using Belviq may not realize that other co-administered substances (e.g. pharmaceuticals, supplements, etc.) may potentiate the severity of certain side effects and/or provoke serious adverse interactions. Unless other co-administered substances administered are confirmed (by a doctor) to be medically necessary and safe, it’s probably a good idea to discontinue them while taking Belviq. Not only can certain co-administered substances alter the pharmacokinetics and neurochemical effects of Belviq, they may cause side effects of their own – making it difficult for users to know whether the side effects they’re experiencing are from Belviq or the other substance.
  4. Adjunct substances: In some cases, it may be helpful to administer adjunct substances to combat unwanted side effects from Belviq. For example, someone dealing with severe bouts of diarrhea may benefit from administration of an adjunct antidiarrheal agent (e.g. Imodium). As a second example, a person dealing with medication-induced nausea and/or vomiting may want to consider an antiemetic adjunct.  Work with your doctor to pinpoint the most debilitating side effect(s) that you’re experiencing during Belviq treatment, and ask whether any adjuncts can be used.  Always ask your doctor to verify that any adjunctive agents you plan on using with Belviq will be safe.
  5. Dosage reduction: It is understood that the greater the dose of Belviq a person takes, the more likely he/she is to experience side effects. This is because larger doses exert a more substantial effect upon the user’s neurochemistry and physiology. Belviq is manufactured in 10 mg pills that are intended to be administered twice per day (b.i.d.).  Anyone deviating from standard dosing recommendations such as by taking supratherapeutic amounts (e.g. 20 mg, b.i.d.) – will be at greater risk for serious side effects.  If you are taking supratherapeutic amounts of Belviq, reducing your dose back to the standard amount (10 mg, b.i.d.) should mitigate side effect severity.  Additionally, it should be noted that for some users, even the 10 mg (b.i.d.) dosing is too potent to handle.  For this reason, if considered safe by your doctor, it may be helpful to split 10 mg pills for a reduced dosing regimen of 5 mg (b.i.d.).  Although the lower dose may be less effective for weight loss, it could significantly improve tolerability.  Moreover, starting at a lower dose (e.g. 5 mg, b.i.d.) and gradually titrating up to 10 mg (b.i.d.) may be helpful for decreasing side effects associated with adaptation of the CNS to the drug.
  6. Lifestyle changes: It is known that factors such as dietary intake, exercise, sleep, and stress can make it easier (or tougher) to tolerate the side effects of Belviq. Someone eating a nutrient-dense diet, getting just enough exercise, with good sleep hygiene and low stress may have an easier time tolerating side effects – compared to a person eating junk food, remaining sedentary (or over-exercising), with poor sleep and high stress. This is because inadequate nutrition/caloric intake, lack of exercise, high stress, and poor sleep – cause side effects of their own that may overlap with and/or exacerbate those of Belviq.  You may find that side effects of Belviq decrease as a result of correcting nutrient deficiencies, optimizing exercise, reducing stress, and/or improving sleep quality.
  7. Continue using: Among individuals that are experiencing unwanted side effects during the first few days and/or weeks of treatment with Belviq, continued usage of the drug may inevitably decrease side effect number and/or severity. In early days of treatment, Belviq administration disrupts homeostatic neurochemical and physiological functions, ultimately provoking side effects. As a person continues treatment for a couple months, his/her neurochemistry and physiology should adapt to expect regular administration of Belviq.  Assuming you give your CNS enough time to adapt to Belviq, you may notice that certain side effects diminish and/or completely disappear.

Have you experienced Belviq (Lorcaserin) side effects?

If you’ve taken Belviq, be sure to report any side effects that you experienced in the comments section below.  To help others get a better understanding of your situation, provide additional details such as your:  Belviq dosage (e.g. 10 mg, b.i.d.), duration of usage, genetic polymorphisms (e.g. CYP450 enzymes) administration details (whether taken with food or without food, timing, etc.), co-administered substances (dietary supplements, drugs, etc.), and other medical diagnoses.  In your experience, which side effects did you find to be most debilitating?

On a scale of 1 to 10, (with 1 being least severe and 10 being most severe), what numeric rating would you assign to each of your side effects?  Did your side effects emerge in the early days of treatment (e.g. within a day or two of your first dose) OR only after you had been taking Belviq for a longer duration (e.g. weeks or months)?  If you experienced side effects in the early days of treatment, did they improve with continued Belviq administration?

For extremely long-term users, did any side effects emerge only after an extended duration (e.g. cardiac complications after 2 years)?  In addition to the side effect mitigation strategies listed above, feel free to share any ways you’ve managed to cope with and/or reduce Belviq side effects without compromising your safety and/or the drug’s efficacy.  Also note whether you’ve found the therapeutic weight loss induction by Belviq to outweigh its side effects – or vice-versa.

Understand that although the FDA considers Belviq to be safe and effective for weight loss [among individuals with high BMIs], not every user tolerates it well.  If you are struggling to tolerate the side effects of Belviq, you may want to discontinue treatment and/or consider alternative weight loss interventions.

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{ 1 comment… add one }
  • Ruby Nickelson September 29, 2016, 5:19 pm

    I have had extreme fatigue, falling asleep at work, dizziness, confusion and insomnia. I have been taking the medication for 6 days 10mg BID.

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