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Namenda (Memantine) Side Effects & Adverse Reactions

Namenda (Memantine) is a drug that was approved by the FDA in 2003 for the treatment of Alzheimer’s disease.  Research suggests that Namenda has a small effect in reducing symptoms among those diagnosed with moderate or severe cases of Alzheimer’s.  It appears to have no significant effect when administered to individuals diagnosed with milder cases of Alzheimer’s.

The drug has a complex mechanism of action, but primarily targets the NDMA glutamatergic receptors with the aim of correcting potential glutamate dysfunction.  It also elicits a modest effect upon the 5-HT3 serotonergic receptor, various nAChRs (nicotinic acetylcholine receptors), and the D2 dopaminergic receptor.  For most individuals, Namenda is thought to be well-tolerated with a favorable side effect profile.

That said, some individuals will notice that taking Namenda leads to unwanted side effects.  Should you experience unwanted side effects from Namenda, it is important to consider whether the benefit derived from the drug outweighs the bother of the side effects.  In some cases, the side effects may be so debilitating that discontinuation or a medication change is warranted.

Factors that influence Namenda side effects

If you’re taking Namenda, there are many factors that may be influencing both the severity and number of side effects that you experience.  These factors include: individual variation, dosage, time span over which you’ve taken the drug, and whether you’re taking any other drugs or supplements.

1. Individual variation

It is important to consider the fact that there’s significant individual variation in regards to side effects experienced while taking Namenda.  Some people may experience very minimal side effects, while others may feel absolutely miserable when taking the drug.  Everyone has a completely unique physiology, genetics, and lifestyle.

It is a combination of these factors that will influence whether you will experience significant or minimal side effects while taking Namenda.  People that are getting steady exercise, eating a healthy diet, getting proper sleep, and maintaining a low-stress lifestyle are likely to experience less side effects than someone who’s the opposite.  In some cases, people may have genetics that don’t interact well with Namenda, leading to severe side effects.

2. Dosage

As a general rule of thumb, the greater the dose of Namenda you’re taking, the more likely you’ll be to experience side effects.  The standard starting dosage is 5 mg per day, but most individuals are titrated upwards to 10 mg, 15 mg, or 20 mg.  Side effects are more likely to occur at greater doses simply due to the fact that more of the drug will be circulating throughout your nervous system and making changes to your brain.

The stronger the dose, the more influence the drug will have over your physiology.  If you’re taking an extremely low dose, you reduce the likelihood of severe side effects.  In other words, someone who’s only taking 5 mg per day probably won’t experience as many side effects as someone who’s taking a full 20 mg per day.  To reduce the potential for side effects, it is always recommended to take the minimal effective dose.

3. Time Span

The side effects that you experience may occur on a short-term basis, after a moderate term of being medicated, or after a long-term.  The severity and number of side effects that you experience may change throughout your course of treatment.  Many people note initial side effects when they begin adjusting to the drug, but find that some of those side effects may fade after several weeks or months.

  • Short-term: Anyone that’s just starting Namenda may experience side effects as their physiology and brain adapt to the drug. Anytime you’re introducing a new stimuli to your nervous system, you’re likely to experience side effects as a result of the changes being made.  Many short-term side effects will fade as your physiology acclimates itself with the drug.
  • Moderate-term: Some people may find that side effects emerge after a moderate term of treatment. In other words, they may not have experienced any noticeable effects when they started the drug, but certain side effects emerged after several weeks or months of treatment.  Most moderate side effects are a sign of what you’ll experience over the long-term.
  • Long-term: Side effects that occur after a long-term (e.g. a year or two) of treatment may be a result of the changes that the drug has made to your nervous system over time. After a long-term of treatment, many people become tolerant to low doses and need to titrate their dosage upwards to get a therapeutic effect.  The increased dosages and increased changes over an extended period of time are responsible for long-term side effects.

Note:  It is important to realize that you may experience short-term side effects that differ from moderate-term side effects, and moderate-term side effects that differ from long-term side effects.

4. Interactions

If you are taking any other drugs or supplements with Namenda, it is important to consider the possibility that there’s an interaction.  Many psychiatric drugs may have contraindications with Namenda.  If you suspect that a drug or supplement you’re taking is interacting with Namenda, talk to your doctor (or a medical professional) and ask.

Even in the event that some drugs or supplements are considered “safe” to take along with Namenda, it is important to consider the possibility that there’s an interaction effect.  For this reason, you may want to try taking Namenda as a standalone drug (without other supplements or drugs) and determine whether any side effects dissipate.  If the side effects dissipate when you eliminate extracurricular supplementation, they may have been a byproduct of an interaction.

Namenda Side Effects: List of Common Reactions

Below is a list of possible side effects that you may experience while taking Namenda.  Understand that both the severity and number of side effects you experience is largely subject to individual variation based on the aforementioned factors.

  • Aggression: Although relatively uncommon, some individuals may become aggressive when taking Namenda.  The specific mechanisms behind the aggression are unknown, but altering glutamate, serotonin, acetylcholine, and dopamine may play a role.  Some individuals may become aggressive as a result of effects on the D2 receptor, while others may not respond well to the antagonist effect on the NMDA receptor.
  • Agitation: In some cases, people may become agitated and unable to sit still while taking Namenda.  For certain people the agitation may fade as they adapt to the drug, while for others it may worsen over time and/or as the dosage is increased.  Should an individual become excessively agitated, a medication change may be warranted.
  • Anxiety: Due to the fact that Namenda affects many different neurotransmitters, there’s always a possibility that it could provoke anxiety.  An individual taking this drug may feel nervous, restless, and tense.  This anxiety may lead to other side effects such as insomnia and interfere with sleep quality.
  • Body pain: Pain throughout the body has been reported as a side effect by those taking Namenda.  While the lower back is the most common site for experiencing the drug-induced pain, it may occur anywhere.  Some people have reported pain throughout their head, while others may feel pain sensations in their arms or legs.
  • Cognitive impairment: Ironically, a drug being used to help improve cognitive function among those with Alzheimer’s doesn’t always do the trick.  In some cases, it can actually result in worsened cognitive function.  It is important to understand that some people may not get any benefit from Namenda, while others may experience an even greater degree of impairment.
  • Confusion: Among the most common side effects associated with Namenda is that of confusion.  People taking the drug may become confused, forgetful, and spaced-out.  This confusion may be mistaken for a worsening of Alzheimer’s or dementia, when in reality it’s a byproduct of the drug.
  • Constipation: Certain individuals may end up dealing with constipation as a side effect.  There may be some individual tweaks in terms of diet and/or laxatives that can be administered to help reduce constipation.  Always talk to your doctor and determine what can be done if constipation becomes overwhelming.
  • Coughing: If you begin taking Namenda and suddenly start coughing, it may not be a “cold.”  In fact, coughing is a fairly common side effect.  For many people the coughing isn’t severe enough to warrant medication discontinuation.  However, if you notice that the coughing is incessant and severe – talk to your doctor.
  • Depression: Not everyone will experience improved cognition and improved mood when they take Namenda.  Many people find that the NMDA antagonist effect makes them more depressed than usual.  Additionally if a person is experiencing confusion, brain fog, or fatigue as a side effect – it may exacerbate their depression due to the fact that they can’t think clearly.
  • Diarrhea: Those that don’t experience constipation may end up dealing with the polar opposite – diarrhea.  If you experience “disaster pants” while taking Namenda, you may want to talk to your doctor about what can be done.  In many cases, purchasing some over-the-counter Imodium may prove beneficial.
  • Dizziness: The single most common side effect associated with Namenda as reported by the manufacturers is dizziness.  Dizziness is a relatively vague side effect associated with many drugs that affect the brain.  Some people may notice a subtle dizziness, while others may feel as if they just got off of a spinning carnival ride.
  • Fatigue: Another relatively common side effect is that of fatigue.  The fact that Namenda acts as an NMDA receptor antagonist reduces the potential for excitotoxicity, but not everyone taking this drug may be dealing with excitotoxicity.  This may lead to understimulation of the NMDA receptor, leading to extreme fatigue.
  • Hallucinations: Some individuals report experiencing hallucinations while taking Namenda.  The hallucinations likely stem from the NMDA receptor antagonist effect elicited by the drug, but may also result from effects on other neurotransmitters.  If you start hearing voices or seeing strange objects with no basis in reality, realize that this is a side effect.
  • Headache: It is estimated that nearly 6% of Namenda users will experience headaches as a side effect.  Some people report severe “head pain” which may be different than a standard headache.  To combat the headaches you should stay hydrated, get plenty of sleep and focus on nutrition.  Taking an over-the-counter headache relief drug may be helpful as well.
  • Hypertension: Another side effect that you may experience is that of hypertension or “high blood pressure.”  An estimated 4% of users will experience a noticeable increase in blood pressure.  If you are concerned about the increase, talk to your doctor as they may be able to devise a strategy to keep your blood pressure within a normal range.
  • Insomnia: You may find that Namenda interferes with your ability to fall asleep and stay asleep.  Insomnia is a common symptom among those who experience anxiety when taking the drug.  Reports suggest that it is less common to experience insomnia from Namenda than sleepiness and fatigue.
  • Libido changes: Those taking this drug may notice that their libido increases or decreases.  This increase or decrease in sex drive may stabilize as you adapt to the drug, or may persist throughout treatment.
  • Memory impairment: Namenda is supposed to help improve cognitive function and memory, but not everyone experiences this improvement.  Some experience no significant benefit, while others may actually find that it exacerbates their initial impairment.  If your memory actually worsens while taking this drug, you may want to reevaluate your treatment.
  • Nausea: Some people report significant nausea when they first start taking Namenda.  For others, this nausea may persist throughout treatment and lead to vomiting.  If you become severely nauseous on Namenda, you may want to talk to your doctor about reducing the dosage and/or considering other options.
  • Pain: You may notice that after you start Namenda, you feel pain throughout your body.  The pain may be concentrated in a specific area or affect one side of your body more than the other.  For other individuals, the pain may be widespread.  Should this pain interfere with your daily functioning, talk to your doctor.
  • Shortness of breath: Another symptom that is less frequently reported is shortness of breath.  If you feel like you’re unable to breathe or as if your respiratory functioning has changed since taking Namenda, it is advised to seek medical attention.  This may be a normal reaction that stabilizes over time, but may also be indicative of something more serious.
  • Sleepiness: Some individuals may find that Namenda makes them extremely tired.  If you feel so tired while taking Namenda that you can’t get out of bed, talk with your doctor about alternative options.  Why take a drug that makes you want to sleep the rest of your life away?
  • Vomiting: Approximately 3% of those taking Namenda will end up vomiting.  Those who vomit may feel nauseated when the begin taking the drug, and the nausea may be a root cause.  If you experience vomiting as a side effect, it is important to tell your doctor as this may be indicative of a serious adverse reaction.
  • Weight changes: Some individuals may experience weight gain while taking Namenda, while others will lose weight.  Side effects such as fatigue and sleepiness may reduce metabolism and activity levels – leading to weight gain.  Other side effects such as restlessness and agitation could lead to weight loss.

Namenda Severe Side Effects / Adverse Reactions

Some people taking Namenda will experience severe side effects and/or adverse reactions.  Keep in mind that severe adverse reactions are relatively uncommon, but have been reported.  Should you experience any severe side effects, it is recommended to consult a medical professional.

  • Allergic reaction: In extremely rare cases, some people may have an allergic reaction to the drug.  This may be accompanied by a skin rash, itching, and swelling of various bodily regions.  For example, you may notice that your tongue or face appears swollen. In this case, immediate medical attention is required.
  • Blood pressure changes: While high blood pressure is considered a fairly common side effect, low blood pressure isn’t.  If you experience significant fluctuations in your blood pressure (e.g. high or low), it may be a serious health risk.  Not everyone can physiologically tolerate blood pressure fluctuations stemming from Namenda.
  • Chest tightness: Some people experience chest tightness while taking the drug.  They may feel as if their respiratory system and ability to take deep breaths is compromised.  Generally chest tightness is accompanied by difficulty breathing.
  • Delusions: In rare cases, individuals may experience delusions or beliefs with no basis in reality.  There are many types of delusions that a person could experience as a result of an adverse reaction to Namenda.  These should be documented and immediately reported to a professional.
  • Difficulty breathing: Another relatively uncommon adverse reaction is difficulty breathing.  If you notice that your respiratory functioning seems impeded or compromised while taking Namenda, it should be discussed with a doctor.
  • Flu-like effects: You may notice that you feel sick while taking Namenda.  A combination of the dizziness, headaches, pains, nausea, and possible vomiting may resemble the flu.  In some cases the flu-like effects will ease up after a few weeks of treatment, but in other cases they may become more severe.
  • Hallucinations: If you’ve been taking Namenda and experience continuous hallucinations, it may not be a good fit for your particular neurochemistry.  The hallucinations may be severe and may result in the adjunct prescription of an antipsychotic drugs.  These medications are known to further impair cognitive function and memory.
  • Muscle weakness: Some individuals experience extreme muscle weakness while on Namenda.  If you feel as if you’re unable to perform normative physical tasks such as walking due to weakness, you should discuss it with your doctor.
  • Numbness: You may feel as if certain body parts have become numb or lost sensation.  This numbness may be due to Namenda-induced neurophysiological changes.  Realize that if your body starts to tingle or feels numb, you should report it to your doctor.
  • Seizures: Certain people may experience seizures while taking Namenda.  Those experiencing seizures may be taking too high of a dose and/or find that their unique neurological footprint doesn’t interact well with Namenda.
  • Urination problems: Various urinary problems have been reported among Namenda users including incontinence and infrequent urination.  You may feel as if you’ve lost bladder control while on the drug or you may notice that you’re rarely urinating compared to you did before taking the drug.

Namenda: Comparing the Benefits (Pros) and Side effects (Cons)

For certain individuals with moderate or severe Alzheimer’s disease, Namenda can be an extremely beneficial medication.  There is some preliminary evidence suggesting that it may decrease overall deterioration and elicit favorable effects on cognitive function, mood, and behavior.  It is also thought that the drug can improve daily performance among those that have Alzheimer’s.

That said, not everyone will be a good fit for Namenda.  In fact, some people will take the drug, experience an array of side effects without any therapeutic effects.  Others may take the drug and notice subtle therapeutic effects, but overwhelming side effects and/or adverse reactions.  In any case, it is important to compare the benefits you’re getting from Namenda with the side effects.

Among individuals that are experiencing worsened cognitive function and memory as a result of Namenda, it may be appealing to discontinue treatment and/or test a different medication.  Individuals that experience minor side effects, but derive significant benefit from Namenda will likely want to continue treatment.  However, those that experience only side effects without any noticeable performance improvement may justify discontinuation.

Have you experienced side effects from Namenda?

If you have experience taking Namenda, feel free to share a comment regarding your side effects.  Mention the dosage you were taking, whether you had moderate or severe Alzheimer’s disease, and whether it may have interacted with other drugs.  You may also want to note how long you had been using Namenda and whether the side effects may have been due to an interaction with another medication and/or supplement.

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5 thoughts on “Namenda (Memantine) Side Effects & Adverse Reactions”

  1. I was put on it for Fibromyalgia and anxiety! It was awesome, however, I started gaining weight! Then after being on 10 for 2 weeks I started messing up at work. Maybe I was just in vacation mode and I hope that’s all it was BC the fog from fibromyalgia is gone.

    When I get angry I get a fog and do things, but don’t remember doing them. Like closing a check or taking a call and I have to go back and make sure it was right. On the Namenda I don’t have that AT ALL. All fog is gone and cognitive function is back. I can concentrate now! Yaaay.

  2. Hi! My daughter took memantine for migraine prophylaxis for a few weeks. It had a significant effect on her cognitive functioning. She was spaced-out, extremely anxious, did not know where she was, would brace herself against the walls for 5-10 seconds at a time staring with her mouth open, was fearful we were going to die in a car crash or that we were hurt if she heard us talking in a different room, confused, and totally out of it/unable to function for 4-6 hrs in the later afternoon to early evening daily.

    She had titrated up to 10 mg/day and was supposed to get up to 20mg per day when we decided to stop using it. She still had migraines every other day. She stopped it 9 days ago. Today out of the blue she had another memantine moment.

    She had a headache 6/10 ramping up, and then said she felt strange, and then felt disconnected from her body… couldn’t tell if she was hungry or full, in pain or not… and then started staring up at the ceiling and not sure where she was.

    She was very mellow and in a good mood but definitely out of it and unable to drive. It was completely unexpected and I have a call in to the Dr to discuss. It went away after about 30-45 mins and now she is back to normal and cheery with a 6/10 headache still. VERY VERY WEIRD.

    Forgot to add… she is 20 yrs old. Also the ONLY reason she is taking this med is for migraines. Not to make her act like she has Alzheimers. Yikes. Need the pain to go away and that is an understatement. SH

  3. My father had been on 10mg of Memantine for 2 years and just two weeks ago his Dr increased it to 15mg and this week he increased it to 20mg. My father suffers from Alzheimer’s disease and since the increase of this drug I have noticed his mood to be much lower, depressed. He is confused for the entire day and cannot string sentences together.

    He is tired and wants to sleep all day but then can’t sleep throughout the night which is exhausting. For the past 2 years he has had a constant cough too, which I just read is another side effect of this drug, but am not sure if it is the only cause of his cough. If these side effects continue much longer I will have to reduce his dosage back to 10mg. Sigh.

  4. Have been on 10 mg memantine twice a day for 15 days for migraine prevention. Have had 3 migraines during this time, severe. Most notably, I have body pain and weakness, stiff neck and sore muscles, a red rash on my chest and severe fatigue.

    I feel a “looming headache.” I am going to try to stop taking this “preventative” if I can find out how to wean off of it without going through withdrawals. I really don’t thank no this is an effective option for me.

  5. Started taking Namenda Titration Pak 5-10 mg on 6/29/16, during the 4th week 7/20/16, was taking 10mg twice a day, and my face started peeling, itching and red with bumps. Stopped taking it on 7/23/16 and began taking Benadryl. On 7/25/16 rash was worse, face and neck swollen and with given prednisone.

    It calmed the face down but can not put anything on my face, no moisturizers, soaps, ointments, creams etc, nothing otherwise face gets worse, redness, bumps and swollen. I’ve been to neurologist, allergist, dermatologist and ears, nose & throat doctors, no one knows why I’m still having the allergic reaction on my face from Namenda. Today is September 28, 2016, I’m still on prednisone and still having same issue. Please help!


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