Gabapentin Interactions with other medications and substances

Gabapentin can interact with other prescription and over-the-counter medications, vitamins, and herbal supplements.

People should be sure to give a doctor a full list of their current medications and supplements before taking gabapentin.

The results of another 2017 review suggest that the following are some of the main substances that interact with the drug:

    • caffeine, which is present in tea, coffee, and cola
    • ethacrynic acid, which is a diuretic
    • losartan, which is a medication for high blood pressure
    • magnesium oxide, which is a mineral supplement and antacid
    • mefloquine, which is an antimalarial drug
    • morphine, which is an opioid pain medication
    • phenytoin, which is an anti-seizure medication

If gabapentin causes sleepiness, a person should speak with a doctor before taking other medications that can also cause drowsiness, including:

    • antianxiety medications
    • antidepressants
    • antihistamines
    • cold and flu medications
    • muscle relaxers
    • narcotics, which are pain medications
    • sleeping pills

Presence of other health conditions

To ensure that gabapentin is safe to take, a person should tell a doctor if they also currently have or have ever had:

    • diabetes
    • dialysis treatment
    • drug or alcohol misuse issues
    • heart disease
    • kidney disease
    • liver disease
    • seizures (if taking gabapentin for conditions unrelated to seizures)

What is the maximum daily dosage of Gabapentin?

I’m taking 800mg three times a day for anxiety. It works great. The max recommended dose is 3600mg daily, but I’ve read where some people take up to 4800mg a day. I guess it depends on the person and how they metabolize it.

Although the FDA says 3600mg/day in most places, they have a more extensive doc about gabapentin/neurontin usage and bioavailability. First, your body can only process a certain amount taken and the rest is excreted, so large doses over their bioavailablity chart don’t give larger effects.

Lyrica and other meds have different bioavailability, so use smaller dosages. Since your kidneys do much of the work with gaba/neurontin, you want to make sure you do not have any kidney problems.

A person may need lower doses or not use it due to that. Second, calcium channel meds like gabapentin are nonlinear, so side effects and benefits vary from person to person.

What works or doesn’t work for one, may be the opposite for another. That is why dosage benefits and side effects vary so much from person to person. Even a small dose might make you sleep, but not to another person.

I have heard from some people their doc may prescribe smaller doses during the day and a larger dose at the time of day more problems appear such as at night.

Gaba/neurontin has a short half life so needs doses spread out during the day. One challenging thing is that people that are on gaba are also on other meds too, so there is going to be confusion about what caused what and if there are interactions.

After a couple years, I was only on gaba. For me on maximum dose, I did sleep more, plus several other side effects. It all comes down to finding the most benefit with the least negatives including cost or as docs say, benefits outweigh the risks. Suggest reading more of this forum for a patient viewpoint.

Does Gabapentin cause constipation?

Gabapentin may cause constipation, but it is not a common side effect. In clinical trials of adults taking gabapentin for nerve pain, only about 4% of people reported constipation.

Who may not be able to take gabapentin

Gabapentin is not suitable for some people.

To make sure it’s safe for you, tell your doctor if you:

    • have ever had an allergic reaction to gabapentin or any other medicine
    • have ever misused or been addicted to a medicine
    • are trying to get pregnant or are already pregnant
    • are on a controlled sodium or potassium diet, or your kidneys do not work well (gabapentin liquid contains sodium and potassium, so speak to your doctor before taking it)

Some people in these trials took an inactive medicine (placebo). About 2% of people taking a placebo also reported constipation, so the actual percentage of people with constipation while taking gabapentin is probably less than 4%.

In clinical trials of people aged 12 and over taking gabapentin for seizure disorder, about 2% reported constipation as a side effect. Out of people taking a placebo, 1% also reported constipation.

In the clinical trials of gabapentin to treat nerve pain in adults, the most common side effects were:

  • Dizziness
  • Sleepiness
  • Swelling in the hands or feet (peripheral edema)

In clinical trials of people older than 12 taking gabapentin to treat a seizure disorder, the most common side effects were sleepiness and clumsiness (ataxia).

Thoughts of death or suicide is another rare but important side effect of gabapentin, occurring in about 1 in 500 people. These thoughts can happen within one week of starting gabapentin. Call your doctor right away if you have any unusual changes in mood or behavior, or any of these symptoms:

  • Thoughts about suicide or dying
  • Suicide attempt
  • Depression, new or worsening
  • Anxiety, new or worsening
  • Panic attacks

In 2019, the U.S. Food and Drug Administration (FDA) added another important warning about gabapentin: When this drug is taken with opioid pain medication or used by a person with chronic lung disease like chronic obstructive pulmonary disease (COPD), it may cause severe and possibly fatal difficulty breathing (respiratory depression). Before starting gabapentin, let your doctor know if you are taking any opioid drug, or if you have been diagnosed with a lung disease.

Even if you have side effects from gabapentin, it is important not to stop taking it suddenly on your own. This medication must be reduced over time (tapered) by your doctor. Stopping suddenly can lead to withdrawal symptoms such as:

  • Anxiety
  • Insomnia
  • Nausea
  • Pain

If you are taking gabapentin to control seizures, stopping suddenly may increase your risk of a seizure.

Does gabapentin help you sleep?

Gabapentin is a prescription medication that may help you sleep. That may be why it has been prescribed for people with insomnia, even though it is not approved for that use.

Gabapentin is available on prescription. It comes as tablets, capsules and a liquid that you swallow.

Key facts

  • You’ll usually take gabapentin 3 times a day. You can take it with or without food.
  • Most people who take gabapentin do not get any side effects. But some people may feel sleepy, tired and dizzy. Common side effects are usually mild and go away by themselves.
  • It takes at least a few weeks for gabapentin to work.
  • Most people do not have to stay on the same brand of gabapentin as there’s very little difference between brands.
  • Some people can become addicted to gabapentin after taking it for a long time. When stopping gabapentin you’ll need to reduce your dose gradually to avoid withdrawal symptoms.
  • If you have epilepsy, you are entitled to free prescriptions for all the medicines you take, not just your epilepsy ones. You can get an application form from your doctor’s surgery.

However, gabapentin enacarbil (Horizant) has been approved by the Food and Drug Administration (FDA) to treat a sleep disorder called restless legs syndrome (RLS).

  • One of the most common side effects of gabapentin is drowsiness.
  • In people taking gabapentin for its approved conditions (certain epileptic seizures and postherpetic neuralgia), 19% of patients older than 12 years of age with epilepsy and 21% of patients with postherpetic neuralgia reported drowsiness as a side effect.

Gabapentin and sleep

Most studies show that gabapentin improves slow wave sleep (“deep sleep”) and total sleep time.

  • Two small studies showed that gabapentin may help people with primary insomnia and occasional sleep disturbance improve total sleep time and wakefulness in the morning.
  • In other studies, it appears that gabapentin may improve sleep in people with other medical conditions that make it more difficult to sleep, such as alcohol dependence, hot flashes and bipolar disorder.

In a large review of 26 studies on gabapentin and sleep in patients with other medical conditions, the average dose taken daily was about 1,800 mg. Although positive sleep outcomes were reported, the researchers noted that gabapentin was not tolerated as well as placebo and some patients stopped taking it. Misuse and abuse of the drug has also been reported.

It takes about 2 to 3 hours for immediate-release gabapentin to reach its fullest effect, and it’s typically taken 3 times per day.

RLS treatment

Gabapentin may also be used to treat RLS, a disorder that makes it hard to fall asleep or stay asleep. RLS causes an uncontrollable and uncomfortable urge to move your legs, which is worse at night.

The FDA has approved gabapentin enacarbil (Horizant) — a long-acting gabapentin — as a treatment for RLS.

Side effects of gabapentin

The most common side effects with gabapentin include:

  • Clumsiness
  • Viral infection
  • Drowsiness
  • Nausea and vomiting
  • Speaking difficulties
  • Tremor
  • Swelling, usually involving the legs and feet
  • Fatigue
  • Fever
  • Movements that are jerky
  • Coordination difficulties
  • Double vision
  • Unusual eye movement
  • Serious reactions can include:
  • Difficulty breathing
  • Allergic reactions with swelling of the throat or face

Is gabapentin a narcotic/controlled substance?

The anti-seizure medication gabapentin is not currently considered a narcotic or controlled substance by the federal government, but certain states have enacted legislation so that the medication is treated as one or monitored by the state’s prescription drug monitoring program.

The use of a controlled substance is regulated by the federal government to prevent abuse or misuse. Prescription drug monitoring programs track prescriptions of certain medications to flag individuals who may be misusing them and at risk of an overdose.

In addition to preventing seizures in individuals with epilepsy, gabapentin may be prescribed to treat nerve or neuropathic pain caused by herpes virus or shingles in adults.

Gabapentin may be considered as an alternative to opioids, which can be highly addictive and result in overdoses and death. Often prescribed to treat pain, opioids are a controlled substance. Gabapentin is known as an opioid potentiate because it can increase the high felt with opioids such as fentanyl, oxycodone, hydrocodone, codeine, morphine and even the street drug heroin.

As a result, gabapentin has potential for misuse or abuse. The combination of opioids and gabapentin may increase the risk of dying from an overdose likely due to depressed breathing. Individuals with chronic obstructive pulmonary disease (COPD) and the elderly are at greatest risk of dying from this combination.

What happens when you suddenly stop taking gabapentin?

Case reports have shown that gabapentin withdrawal can last for up to 5 days or longer, but the duration has not been well established in human studies. The symptoms and how long they last depend on how much of the drug you are taking and for how long you’ve been taking it.

Gabapentin withdrawal is not a common problem unless you are abusing the drug.

Abuse means taking gabapentin in higher than prescribed amounts and taking it for reasons not intended by your doctor.

A study on gabapentin abuse from 1993 through 2015 showed that people who experienced withdrawal were taking an average of 3,000 mg (600 to 8,000 mg) of gabapentin per day, but some case reports mention withdrawal symptoms at 400 mg per day.

What happens when you suddenly stop taking gabapentin?

If you are taking gabapentin at a normal dose prescribed by your doctor and you don’t have a history of substance abuse, you are less likely to have withdrawal symptoms when you stop taking it.

Higher doses and a history of substance problems pose more risk for abuse. You can start to build up a tolerance to the drug, and you may need to take even more of it to get the desired effect. This is called physical dependence.

Your brain cells (neurons) become dependent on a high dose of the drug for normal functioning. When the drug is stopped, your brain becomes temporarily disorganized. If you start to feel that you need more of the drug to function, stopping suddenly is more likely to lead to withdrawal symptoms.

Withdrawal symptoms may start within 12 hours or take up to 7 days to begin after stopping suddenly. Symptoms commonly include:

      • Restlessness (agitation)
      • Disorientation
      • Confusion

Various case reports describe these other symptoms of gabapentin withdrawal:

  • Headache
  • Body/stomach pain
  • Anxiety
  • Heart palpitations
  • Sweating
  • Muscle twitching
  • Light sensitivity
  • Restless limb movements
  • Nervousness

What is the treatment for gabapentin withdrawal?

There are no approved medications to treat gabapentin withdrawal. The only reliable treatment is to slowly taper the drug under the supervision of your doctor, usually a substance abuse specialist. Sometimes gabapentin is restarted to ease withdrawal symptoms before tapering off.

There is no evidence to show that other drugs or supplements — such as magnesium or CBD oil — are helpful in treating withdrawal symptoms.

Most case reports show that withdrawal patients went back onto gabapentin to relieve their symptoms. But there may be unreported cases of gabapentin withdrawal, as not everyone seeks treatment.

How can I avoid gabapentin withdrawal?

The best way to avoid gabapentin withdrawal is to only take the drug in the dose prescribed by your doctor for its approved uses.

Gabapentin is a prescription medication approved to treat certain types of seizures and nerve pain that follows a herpes infection (postherpetic neuralgia). A long-acting form is used to treat restless legs syndrome. The most common brand name is Neurontin.

Gabapentin is also prescribed and used for unapproved reasons. These are called off-label uses. Off-label uses for gabapentin include:

  • Substance abuse treatment
  • Migraine headaches
  • Fibromyalgia
  • Mental health disorders
  • Insomnia

People with a history of drug or alcohol abuse may be at increased risk for:

  • Tolerance
  • Self-dose escalation
  • Drug-seeking behavior
  • Withdrawal symptoms

Does gabapentin cause weight gain?

Gabapentin may cause weight gain, but it is a rare side effect. Gabapentin is used to treat epilepsy.

It’s also taken for nerve pain, which can be caused by different conditions, including diabetes and shingles. Nerve pain can also happen after an injury.

In epilepsy, it’s thought that gabapentin stops seizures by reducing the abnormal electrical activity in the brain.

With nerve pain, it’s thought to block pain by affecting the pain messages travelling through the brain and down the spine.

Gabapentin is available on prescription. It comes as tablets, capsules and a liquid that you swallow.

Studies have shown that a small number of people taking gabapentin, a drug used to treat epilepsy and postherpetic neuralgia, experienced weight gain. People who do gain weight may gain about 5 pounds after 6 weeks of use.

    • In people with epilepsy, weight gain occurred in 3% of people older than 12 years of age who were taking gabapentin (compared to 2% of people taking the placebo). Weight gain was also seen at a similar rate in pediatric epilepsy patients who were 3 to 12 years old.
    • In people with postherpetic neuralgia, 2% of patients taking gabapentin experienced weight gain. No weight gain was found among people taking the placebo.

The cause of weight gain with gabapentin is likely due to increased appetite. You may be hungry more often. In some cases, weight gain may be due to fluid retention, another side effect of gabapentin. Another possible cause is not getting enough exercise if gabapentin is causing fatigue.

Some ways to avoid weight gain include:

    • Eating a healthy and balanced diet
    • Eating smaller portion sizes
    • Avoiding high-calorie snacks and desserts like chips, pastries and sweets
    • Eating low-calorie snacks like fruits and vegetables to manage hunger
    • Getting regular exercise

Swelling from fluid retention may be reduced by:

    • Sitting with your feet raised
    • Avoiding standing for long periods of time

If gabapentin is causing you to gain weight, do not stop taking this drug on your own. Stopping the drug suddenly can lead to serious problems, especially if you are taking gabapentin for seizures. Abruptly stopping a seizure medicine can cause seizures that won’t stop.

Weight gain is one of many possible side effects. The most common side effects with gabapentin include:

    • Clumsiness
    • Viral infection
    • Sleepiness
    • Nausea and vomiting
    • Speaking difficulties
    • Tremor
    • Swelling, usually involving the legs and feet
    • Fatigue
    • Fever
    • Movements that are jerky
    • Coordination difficulties
    • Double vision
    • Unusual eye movement

Detail Side Effects of Gabapentin

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

    1. Clumsiness or unsteadiness
    2. continuous, uncontrolled, back-and-forth, or rolling eye movements

More common in children

    1. Aggressive behavior or other behavior problems
    2. anxiety
    3. concentration problems and change in school performance
    4. crying
    5. depression
    6. false sense of well-being
    7. hyperactivity or increase in body movements
    8. rapidly changing moods
    9. reacting too quickly, too emotional, or overreacting
    10. restlessness
    11. suspiciousness or distrust

Less common

    1. Black, tarry stools
    2. chest pain
    3. chills
    4. cough
    5. depression, irritability, or other mood or mental changes
    6. fever
    7. loss of memory
    8. pain or swelling in the arms or legs
    9. painful or difficult urination
    10. sore throat
    11. sores, ulcers, or white spots on the lips or in the mouth
    12. swollen glands
    13. unusual bleeding or bruising
    14. unusual tiredness or weakness

Incidence not known

      1. Abdominal or stomach pain
      2. blistering, peeling, or loosening of the skin
      3. clay-colored stools
      4. coma
      5. confusion
      6. convulsions
      7. dark urine
      8. decreased urine output
      9. diarrhea
      10. difficult or troubled breathing
      11. dizziness
      12. fast or irregular heartbeat
      13. headache
      14. increased thirst
      15. irregular, fast or slow, or shallow breathing
      16. itching or skin rash
      17. joint pain
      18. large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
      19. loss of appetite
      20. muscle ache or pain
      21. nausea
      22. pale or blue lips, fingernails, or skin
      23. red skin lesions, often with a purple center
      24. red, irritated eyes
      25. unpleasant breath odor
      26. vomiting of blood
      27. yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  1. Blurred vision
  2. cold or flu-like symptoms
  3. delusions
  4. dementia
  5. hoarseness
  6. lack or loss of strength
  7. lower back or side pain
  8. swelling of the hands, feet, or lower legs
  9. trembling or shaking

Less common or rare

  1. Accidental injury
  2. appetite increased
  3. back pain
  4. bloated or full feeling
  5. body aches or pain
  6. burning, dry, or itching eyes
  7. change in vision
  8. change in walking and balance
  9. clumsiness or unsteadiness
  10. congestion
  11. constipation
  12. cough producing mucus
  13. decrease in sexual desire or ability
  14. dryness of the mouth or throat
  15. earache
  16. excess air or gas in the stomach or intestines
  17. excessive tearing
  18. eye discharge
  19. feeling faint, dizzy, or lightheadedness
  20. feeling of warmth or heat
  21. flushed, dry skin
  22. flushing or redness of the skin, especially on the face and neck
  23. frequent urination
  24. fruit-like breath odor
  25. impaired vision
  26. incoordination
  27. increased hunger
  28. increased sensitivity to pain
  29. increased sensitivity to touch
  30. increased thirst
  31. indigestion
  32. noise in the ears
  33. pain, redness, rash, swelling, or bleeding where the skin is rubbed off
  34. passing gas
  35. redness or swelling in the ear
  36. redness, pain, swelling of the eye, eyelid, or inner lining of the eyelid
  37. runny nose
  38. sneezing
  39. sweating
  40. tender, swollen glands in the neck
  41. tightness in the chest
  42. tingling in the hands and feet
  43. trouble sleeping
  44. trouble swallowing
  45. trouble thinking
  46. twitching
  47. unexplained weight loss
  48. voice changes
  49. vomiting
  50. weakness or loss of strength
  51. weight gain

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

How long does it take gabapentin to work?

It can take several weeks for gabapentin to reach its full effect, but this depends on the condition being treated.

Gabapentin is approved to treat:

      • Nerve pain
      • Some types of seizures
      • Restless legs syndrome (RLS)

It also depends on your individual response to the drug. The time gabapentin takes to work is not the same for everyone.

The effective dose of gabapentin is also very different for each person. It may vary from 300 mg per day to up to 3,000 mg per day.

Another reason gabapentin takes time to work is that the dose is usually started low and gradually increased over time to reach an effective dose.

For example, when used to relieve nerve pain, the initial dose may be started at 300 mg and increased by 300 mg daily over several days, gradually reaching up to 600 mg three times per day. Studies for nerve pain treatment show that pain relief may begin within 1 week, with the maximum effect reached after about 4 weeks.

Gabapentin is in a class of medications called anticonvulsants. It is not completely known how this drug works. When used to treat a type of seizure disorder, called a partial onset seizure, gabapentin decreases the abnormal activity in the brain that causes the seizures. When used to treat nerve pain, or neuralgia, following a herpes zoster (shingles) infection, gabapentin may reduce the response to painful stimuli. It is unknown how gabapentin relieves symptoms of restless legs syndrome.

Even though it may take up to 4 weeks to get the full effects of gabapentin, it is important not to stop taking it suddenly. That could cause withdrawal symptoms such as:

      • Anxiety
      • Insomnia
      • Nausea
      • Pain

If you are taking gabapentin to control seizures, stopping suddenly may increase your risk of a seizure.

Common side effects of Gabapentin

These common side effects of gabapentin may happen in more than 1 in 100 people. They’re usually mild and go away by themselves.

There are things you can do to help cope with them:

    • Feeling sleepy, tired or dizzy
    • Feeling sick (nausea)
    • Being sick (vomiting)
    • Diarrhoea
    • Mood changes
    • Swollen arms and legs
    • Blurred vision
    • Dry mouth
    • Difficulty getting an erection
    • Weight gain
    • Memory problems
    • Headaches
    • Getting more infections than usual

Keep taking the medicine, but talk to your doctor if this advice does not help and the side effects bother you or do not go away.