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Does Gabapentin (Neurontin) Cause Weight Gain?

Gabapentin (Neurontin) is a medication that was developed as a treatment for neuropathic pain and as an adjunct for seizures.  It is also commonly prescribed off-label for conditions such as: restless leg syndrome, hot flashes, migraines, and even anxiety disorders.  In fact, an estimated 9/10 prescriptions for the drug are for off-label conditions.

The drug is frequently used off-label due to the fact that it is considered to have a low potential for abuse and is regarded as non-addictive.  Due to the fact that the drug elicits both analgesic and anticonvulsant effects, it is sometimes preferred by those undergoing various types of surgery.  It reduces preoperative anxiety via its mechanism acting on GABAergic neurotransmission, and provides postoperative pain relief.

Although many people find that Gabapentin is an effective treatment for neuropathic pain, seizures, and various off-label conditions – many people experience unwanted side effects.  One unwanted side effect that has been reported in a small percentage of users is weight gain.  Those that gain significant weight on Gabapentin may be tempted to discontinue as a result of a compromised body-image.

Does Gabapentin (Neurontin) Cause Weight Gain?

Gabapentin is a drug that isn’t associated with clinically significant weight gain.  It is estimated that approximately 3% of all users will experience some form of weight gain.  Most people won’t notice any significant fluctuations in body weight throughout their treatment.  For this reason, Gabapentin is often referred to as a “weight neutral” drug.

That said, there are some studies highlighting the fact that weight gain can occur on Gabapentin, especially when taken at high doses.  In one study of 28 patients taking 3000 mg per day of Gabapentin, 10 patients gained approximately 10% of their bodyweight.  Despite this finding, the majority of patients remained weight neutral, and some even lost weight (3 patients).

While more individuals are likely to gain weight as opposed to lose weight on Gabapentin, most individuals won’t notice any significant change in bodyweight.  However, it is important to understand that many pharmaceutical companies underestimate the potential of their drug to cause weight gain in effort to increase sales.  If you end up gaining weight, it may be difficult to distinguish whether it’s a result of the drug or blatantly poor health choices.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/9263379

How Gabapentin Causes Weight Gain: List of Possibilities

Gabapentin has a poorly understood mechanism of action and weight gain is uncommon.  Since there is some confusion regarding the precise neurophysiological effects of the drug, it is difficult to pinpoint the specific cause of weight gain.  There are many theories in regards to why you may pack on some extra poundage while taking Gabapentin.

  • Appetite increase: Some people notice that Gabapentin significantly increases their appetite. If you’ve been taking Gabapentin and have been feeling hungrier than usual, it may be more than a coincidence.  Certain individuals find that they consume more because the drug is increasing their appetite.  An increased appetite can be difficult to control, and as a result, some people gain weight.
  • Arousal reduction: Gabapentin is known to act on the neurotransmission of GABA in the brain. GABA is considered an inhibitory neurotransmitter that reduces activation of the sympathetic nervous system, and ultimately reduces arousal.  Those feeling reductions in physiological arousal may have a difficult time summoning up the energy to start (or finish) a workout.
  • Drowsiness: The most common side effect of Gabapenin is drowsiness. If you feel drowsy each time you take Gabapentin, you probably won’t feel like moving, let alone working out.  This drowsiness may lead to a significant decrease in physical activity and an increase in sedentary behavior.  The lack of physical activity as a result of drowsiness can result in weight gain, especially if your dietary intake remains the same or increases.
  • Fatigue: Some people report that Gabapentin makes them feel exceptionally sluggish and fatigued. This feeling of fatigue may stem from the most common side effect associated with the drug – drowsiness.  If you feel more fatigued than usual, this may trigger a cascade effect of metabolism slowing and physical inactivity.
  • Food cravings: Various anecdotal reports have claimed that Gabapentin increased their cravings for sugary foods and carbohydrates. If you are craving sugary foods and end up following through with consumption of those foods, weight gain is likely.  Consuming excess sugary foods leads to blood sugar changes and metabolic fluctuations; all making weight gain likely.
  • Hormone levels: Any drug that alters brain chemicals and the nervous system has potential to alter hormone levels. While hormone alterations may not be significant or even common among everyone using Gabapentin, the possibility should not be ruled out.  Hormonal alterations may be significant enough to cause weight gain.
  • Low energy: Those experiencing reductions in energy while taking Gabapentin are not alone. Energy reductions commonly occur when individuals take drugs that act on GABA; Gabapentin regulates two enzymes involved in GABA synthesis.  The altered synthesis may result in drowsiness, fatigue, and ultimately low neurophysiological energy.  This low energy may translate directly to packing on some unwanted baggage.
  • Reduced motivation: Staying motivated on Gabapentin may be difficult as a result of the drug’s effect on neurotransmission and physiology. Its effect upon the synthesis of GABA commonly results in drowsiness characterized by decreased cognitive and physiological arousal.  Reductions in arousal commonly result in motivational deficits and/or amotivational behavior.
  • Slow metabolism: Taking any drug that acts on GABA will likely reduce physiological arousal. The reduction in arousal can actually slow your metabolism, leading you to gain weight even without changing your dietary intake or exercise regimen.  In other words, your diet and exercise routine may be the exact same pre-drug as during treatment, but you may still gain weight – this is thanks to the slowing of your metabolism.
  • Social eating: Many untreated medical conditions can result in social isolation, which means you probably aren’t going out to eat with friends as much. Let’s say you start taking Gabapentin for anxiety or neuropathic pain, and are now able to function better in social situations.  As a result, you may start to go out with friends more frequently, eating bigger portions and making unhealthy choices.
  • Taste improvement: It is possible for some people to subjectively notice a change in taste sensation when taking Gabapentin. While extremely unlikely, it is yet another possible explanation for weight gain.  If food all of a sudden tastes significantly better than it did prior to taking the drug, you’re probably going to eat more.
  • Water retention: Some believe that the drug may increase water retention, thus contributing to a weight increase as a result of retained water. This may result in feeling bloated and to some people, the extra weight via water retention may be blatantly obvious.  Unfortunately, there’s not much that can be done to mitigate this side effect.

Note: It is important to note that weight gain on Gabapentin is largely subject to individual variation.  Certain individuals may experience weight gain as a result of a single factor (e.g. food cravings), while others may gain weight as a result of multiple factors (e.g. slow metabolism, fatigue, and appetite increase).

Factors responsible for weight gain on Gabapentin (Neurontin)

There are many factors that may influence weight gain (or change) on Gabapentin.  The most influential factors include: time span (how long you’ve been taking the drug), the dosage, other medications (drugs often interact), your lifestyle, and genetics.

1. Time Span

For some people, the duration over which they’ve been taking Gabapentin will influence their weight gain.  Some people may notice no weight gain when they first start taking the drug, but may start to pack on some extra baggage after a year.  One study suggests that weight gain most commonly occurs between months 2 and 3 of treatment and stabilizes after 6 to 9 months.

  • Short-term:  Those that have been taking Gabapentin over a short-term may notice some temporary fluctuations in body weight as their physiology acclimates to the drug.  These short-term changes tend to occur during the first few weeks of treatment.  While weight gain may be alarming over the short-term, it’s not necessarily what will occur over the long-term.
  • Long-term: It is common for people to report that they gain weight over the course of long-term treatment with Gabapentin.  Long-term treatment with any drug will alter physiological processes and the body becomes more prone to side effects – including weight gain.  Some people take the drug for years without any weight gain, while others notice incremental increases with each successive year of treatment.

2. Dosage

Some literature indicates that there is no established relationship between dosage and weight gain.  Stating that there is no established relationship between dosage and weight gain does not mean that this applies to everyone.  Some people may notice that they’re significantly more prone to weight gain at higher doses.

Those that gain weight on lower doses may experience an amplified effect of weight increases at higher doses.  Therefore it may be a good idea to take the minimal effective dose to minimize potential weight fluctuations.

3. Other Medications

If you are taking any other medications, it’s important to consider the fact that they may be contributing to the weight gain.  Unless you have been on another drug for a long-term and haven’t noted any weight changes, it’s difficult to conclude that Gabapentin is the culprit for your weight gain.  Even if you don’t think another medication is contributing to your weight gain, it is important to consider the potential of an interaction.

Certain mechanisms of action associated with your other medication(s) may interact with the Gabapentin to promote weight gain.  If you started taking another drug simultaneously with Gabapentin and are gaining weight, consider that it may be caused by the other drug.  You may also want to consider other non-pharmaceutical drugs and alcohol as potential culprits.

4. Lifestyle

It is important to consider the influence of your lifestyle on your bodyweight.  Everyone wants to use the latest drug that they’re taking as a scapegoat excuse for their weight gain.  If you are sedentary for most of the day, don’t make any effort to get physical activity, eat unhealthy foods high in carbohydrates and sugars – you shouldn’t be surprised if you gain weight.

While diet and exercise are important elements to consider as causes of weight gain, you may also want to consider sleeping habits and stress level.  Someone getting a poor night’s sleep consistently and/or an individual with high stress is much more likely to gain weight.  Consider lifestyle influences before assuming that Gabapentin is the problem.

5. Genetics

Much of weight gain on medications is subject to genetics.  Take two people with identically healthy lifestyles and put them on the same dosage of Gabapentin for the same duration.  One of those individuals may end up gaining 10 lbs., while the other may lose 5 lbs.  What would explain the difference between these two individuals? Genetics as well as epigenetics or gene expression in response to the environment.

Fortunately new technology is available like GeneSight to help predict genetic responses to various medications.  Genetics influence our physiological reactions to Gabapentin, thus dictating side effects – including whether we gain weight, remain weight neutral, or even lose weight.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/24308788
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/23865122

How much weight will you gain on Gabapentin?

Based on the fact that few studies exist analyzing Gabapentin’s effect on bodyweight, it is difficult to predict how much weight you’ll gain while taking the drug.  One study suggested that those who gain weight will gain between 5% and 10% of their baseline body weight.  In other words, if you weighed 200 lbs. prior to taking Gabapentin and gained weight – you’d probably gain between 10 lbs. and 20 lbs.

In another study published in 2013, the gastroretentive format of Gabapentin was analyzed over the course of 24 weeks.  Patients did report weight gain, but the average weight gain was approximately 1.6 lbs.  This suggests that over the course of 2 years treatment with Gabapentin, weight gain is likely to be minimal among those who do gain weight.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/9263379
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/23370075

Does everyone gain weight from Gabapentin?

Certainly not everyone gains weight while taking Gabapentin.  It is estimated that over 90% of individuals taking the drug will experience no significant weight change.  Of the remaining individuals, some will actually experience weight loss.  Clinical trials suggest that less than 3% of all Gabapentin users will gain weight – this means that only a small number of people 3/100 will gain weight.

Some speculate that more people gain weight than what is reported by the drug company and/or clinical documentation.  This drug is considered a predecessor to Lyrica (Pregabalin), which is associated with weight gain.  There is evidence linking Lyrica and weight gain, suggesting that 10% to 20% of users will gain weight.

Since a greater percentage of Lyrica users gain weight, and Gabapentin is similar – some believe that the reports of weight gain on Gabapentin are low-ball estimates.  Despite these theories, the bulk of scientific evidence suggests that most people will not gain significant weight while taking Gabapentin.  In addition, a very small percentage of individuals will actually lose a bit of weight.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/16397976

Comparing the therapeutic effect vs. weight gain

Among those who gain weight on Gabapentin, it is important to consider the therapeutic effect of the drug.  Always conduct a cost-benefit analysis and determine the severity of the weight gain compared to the benefit derived from Gabapentin treatment.  If you’re getting significant relief from your neuropathic pain and only gained a few pounds over the course of several months, you probably shouldn’t care too much about the weight gain.

However, if you managed to balloon in weight, gaining a significant amount – you may want to talk to your doctor.  At a certain point, weight gain from any medication may get excessive and should be considered unacceptable.  Gaining a significant amount of weight can put you at risk for other health conditions and may be detrimental to your self-esteem – leading to depression.

If you gained a fair amount of weight, but the drug is very therapeutic for a certain condition – you may feel as if you’re in a difficult situation.  Always talk to a medical professional to assess your options that may include: Gabapentin withdrawal and/or switching to another medication.  Certain people may be able to find a different medication that better suits their physiology.

Did you gain weight taking Gabapentin?

If you ended up gaining weight while taking Gabapentin, be sure to share a comment below with some details.  Discuss how long you took Gabapentin, the dosage, as well as any other medications you were taking simultaneously that may have caused you to gain weight.  Share why you believe the drug caused you to gain weight (e.g. drowsiness, food cravings, etc.).

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{ 140 comments… add one }
  • Sara M October 1, 2018, 4:59 pm

    I’ve found everyone’s comments extremely helpful, having been taking Gabapentin for 3 1/2 years, my weight has gradually crept up by at least 2 & 1/2 stone. Definitely weight has gone on from 300mg x3 a day onwards, esp the past year where I have been on 600-900 3x day.

    All the while I couldn’t understand what I was doing wrong, sticking to either calorie counting or ww, exercising daily & doing a gym GP physio referral as well & last week I asked the GP yet again about the weight gain as I’m now overweight & gone up 3 dress sizes, can’t afford £ to keep just buying a bigger size & mentally I’m not handling the weight gain at all.

    Physically it’s causing increased joint pain (widespread osteoarthritis) I was prescribed it for stenosis, prolapsed discs, sciatica & muscular pains & sweats due to the pain! I was getting the bad bloat & distention like people describe.

    The weight gain is almost all round my waist abdomen & hips, it’s not gone on like normal times when I’ve put on a few lbs. After I read the comments on here & discovered I’m not the only one, the GP admitted it’s the Gabapentin that’s probably the culprit if I really do exercise & watch my diet.

    He suggested a lower dose, I cut it out over 2 days completely 4 wks ago today. I’ve lost a little bit & stopped putting any on more importantly & lumping the pain!

    I forgot to add that other side effects I had on the Gabapentin, which I thought would wear off when I got used to taking it, but didn’t – increasingly forgetful, important things like appointments I would completely forget on the day, I was not ‘with it’ at all, thinning hair, better mood alternated with increased anxiety & it affected my speech, some of the time I sounded like I’d ‘had a few.’

    The bedtime dose used to knock me out to sleep & not wake up in pain in the night. Previously I’ve put on weight quick on transfix & beta blockers, which I didn’t take more than a few months & it came back off again.

    I liked the Gabapentin at first, it really sorted out the back pain & sciatica & meant I didn’t need any more epidurals, until the weight gain has crept up on me, it didn’t dawn on me at first as I didn’t change my diet, appetite or exercise, it meant less pain, more exercise & I expected it to even put.

    The weight didn’t start going on until I stopped the thyroid medication I had been on. I was hyperthyroid & it was masking the potential Gabapentin weight gain. Thyroid normal now & all the weight has gone on since, 4 dress sizes now!

  • Kimberly September 25, 2018, 8:19 pm

    I have been on gabapentin for ten months. Started gaining weight a month or so in. It’s been steady, 30 lbs so far. Never had a problem with weight before. It does help with my pain and anxiety. It also causes my sugar cravings I’ve never had before, and my feeling lazy, again never before.

    Don’t think I can handle these side effects and probably won’t try another med to replace this. Had enough.

  • Suzanne September 15, 2018, 4:52 pm

    My experience echoes Mary and Karen. Gained about 8 lbs in two months while training for a sprint triathlon. Gained most of it in a huge wad on my abdomen like a beach ball without the stripes. Moreover it looks like someone stuffed cottage cheese at my armpits. Gabapentin was prescribed for RLS and was not ineffective but every time I saw the doctor, the dose increased. Horrible drug.

  • Gillian September 7, 2018, 9:27 pm

    Always been fit and even though in pain from nerve pain in both feet and legs have continued to go walking. Am on 2400mg a day and have gained 5lbs weight in three months. Not very happy about this.

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