Category: Gabapentin

Gabapentin Overdose and Toxicity

What Is Gabapentin?

Gabapentin is a pharmaceutical medication originally intended for use in the treatment of seizures.

However, gabapentin is most commonly prescribed for conditions other than seizures and epilepsy, such as pain syndromes. Since gabapentin is not an opioid, in theory, it has lower abuse potential and is more readily prescribed for pain than more addictive medications. Gabapentin can also be used to treat:

      • Nerve pain, such as from a shingles outbreak
      • Treating alcohol or cocaine withdrawal
      • Restless legs syndrome
      • Diabetic neuropathy
      • Fibromyalgia
      • Hot flashes

How Does Gabapentin Work?

Gabapentin is a calming chemical that has a similar chemical structure to Gamma-aminobutyric acid (GABA), which is a brain chemical that calms the nervous system. However, gabapentin does not bind to the body’s GABA receptors. Instead, gabapentin affects the body’s calcium channels to reduce seizures and nerve pain.

How Addictive is Gabapentin?

Gabapentin is thought to be less addictive than opioid medications for pain relief. Overall, gabapentin is not considered a highly addictive drug. Many cases of gabapentin abuse occur in people who already have addictions to opioids and other drugs.

In response to increased abuse of gabapentin, some states are classifying gabapentin as a Schedule V controlled substance. While gabapentin appears to have low abuse potential, it is often used in conjunction with other, more addictive, drugs.

It’s possible to fatally overdose on gabapentin. Reports of gabapentin being abused alone, and with opioids, prompted the FDA to release a warning statement (in December 2019) about the fatal risk of respiratory depression. Signs of overdose include:

      • Ataxia (decreased muscle coordination)
      • Diarrhea
      • Drooping eyelid
      • Drowsiness and lethargy
      • Double vision
      • Excitation
      • Hypoactivity
      • Labored breathing
      • Marked sedation
      • Slurred speech

If you suspect an overdose, you need immediate medical treatment. The only way to remove the drug is through kidney dialysis in the emergency room.

Gabapentin Addiction Statistics

A study published in 2013 conducted in Kentucky showed that among 503 participants reporting illegal drug use, 15% reported using gabapentin to “get high” in the previous six months.

That percentage was a 165% increase from the year prior. A national assessment found that nearly a quarter of patients with co-prescriptions of opioids and gabapentin had three or more prescriptions exceeding established dosage thresholds.

In comparison, in patients prescribed just opioids or just gabapentin, the figures were 8% and 3% respectively.

Can You Overdose on Gabapentin?

Despite the well-known withdrawal side effects, it’s difficult to overdose on gabapentin. Studies have shown that even at very high levels of ingestion, people have only suffered mild to moderate physical and mental side effects that are rarely life-threatening. So far, there have been only two peer-reviewed case reports of death  from gabapentin toxicity (related to gabapentin overdose). Despite this low statistic, gabapentin abuse as a suicide attempt has risen over the years.

While this means gabapentin is a relatively safe drug, it still should not be ingested in large amounts. However, people taking gabapentin should be aware that it does have particularly unpleasant withdrawal symptoms, even after taking it for a relatively short amount of time and at low doses.

Symptoms of Gabapentin Overdose

Most side effects of a gabapentin overdose will be related to an overall deceleration of the body’s systems. Drowsiness, muscle weakness, lethargy and drooping eyelids can be expected. Other gabapentin overdose symptoms include diarrhea and sedation. These symptoms arise because gabapentin is formulated to slow down misfirings in the brain that cause seizures.

Those who use gabapentin should be aware that stopping gabapentin abruptly can actually increase the chance of experiencing seizure activity. Suddenly removing the anti-seizure effect can cause a rebound, raising the risk of seizures. Gabapentin is a powerful drug that must be tapered slowly to avoid some of its more severe withdrawal side effects.

Is Gabapentin Considered as Controlled Substance ?

Gabapentin is not currently a controlled substance at the federal level, but certain states have made gabapentin a controlled substance at the state level. This includes Kentucky, Michigan, Tennessee, Virginia and West Virginia.

Does Gabapentin have any warnings when taking the drug?

The FDA has issued several warnings for gabapentin. These include certain side effects like Drug Reaction with Eosinophilia and Systemic Symptoms, or DRESS, and allergic reactions like anaphylaxis or angioedema, a swelling of the lips or face. The drug should be stopped immediately if any of those side effects are suspected. Other side effects that need to be monitored include impaired motor skills, drowsiness, dizziness, mental status changes, slowed breathing and a possible increase in suicide risk.

How is Gabapentin taken?

Gabapentin is taken by mouth. There are various dosage forms of the medication, including capsules, oral solutions and tablets. The drug comes in both immediate-release (IR) and extended-release (ER) formulations.

Does Gabapentin have other names?

Gabapentin may be sold under different brand names, including Neurontin and Gralise.

What ingredients are in Gabapentin?

Gabapentin is part of its own drug class, called gabapentinoids. Typical dosages range from 100 milligrams to 800 milligrams of the drug. Some inactive ingredients in the gabapentin tablets or capsules include:

Gabapentin is not currently a controlled substance at the federal level, but certain states have made gabapentin a controlled substance at the state level. This includes Kentucky, Michigan, Tennessee, Virginia and West Virginia.

Does Gabapentin have any warnings when taking the drug?

The FDA has issued several warnings for gabapentin. These include certain side effects like Drug Reaction with Eosinophilia and Systemic Symptoms, or DRESS, and allergic reactions like anaphylaxis or angioedema, a swelling of the lips or face. The drug should be stopped immediately if any of those side effects are suspected.

Other side effects that need to be monitored include impaired motor skills, drowsiness, dizziness, mental status changes, slowed breathing and a possible increase in suicide risk.

How is Gabapentin taken?

Gabapentin is taken by mouth. There are various dosage forms of the medication, including capsules, oral solutions and tablets. The drug comes in both immediate-release (IR) and extended-release (ER) formulations.

Does Gabapentin have other names?

Gabapentin may be sold under different brand names, including Neurontin and Gralise.

What ingredients are in Gabapentin?

Gabapentin is part of its own drug class, called gabapentinoids. Typical dosages range from 100 milligrams to 800 milligrams of the drug. Some inactive ingredients in the gabapentin tablets or capsules include:

        • Lactose
        • Talc
        • Cornstarch
        • Gelatin
        • Colors such as FD&C blue no. 2, yellow iron oxide
        • Titanium dioxide
        • Poloxamer 407
        • Magnesium stearate
        • Copovidone, cornstarch
        • Candelilla wax
        • Hydroxypropyl cellulose

 

The Role of Gabapentin in Pain Management

Opioids, non‐steroidal anti‐inflammatory drugs (NSAIDs), antidepressants, and anticonvulsants are used as pharmacological agents to treat pain. However, no single class of drugs has been found to be effective in all types of pain, presumably because pain syndromes involve different mechanisms.

In addition, each of the currently available drugs is associated with adverse effects, some of which are potentially serious or life‐threatening such as idiosyncratic or toxic reactions.

Traditionally, the treatment of neuropathic pain has involved anticonvulsants, such as carbemazepine, valproic acid and phenytoin, and tricyclic antidepressants, such as amitriptyline and nortriptyline and doxepin. The main disadvantages of the anticonvulsants are their potential for drug interactions via the induction of hepatic enzymes, or resulting from inhibition of hepatic enzymes by other drugs. Minor side‐effects such as sedation, ataxia, vertigo and diplopia are associated with carbemazepine and phenytoin, whereas, anorexia, nausea, vomiting and tremor are associated with valproic acid. Chronic phenytoin use may cause peripheral neuropathy (30%) and gingival hyperplasia (20%), and fetal hydantoin syndrome if administered during pregnancy. Carbemazepine can cause chronic diarrhoea or the syndrome of inappropriate ADH secretion, and rarely aplastic anaemia, thrombocytopaenia, hepatocellular jaundice and cardiac arrhythmias.

Tricyclic antidepressants also cause side‐effects that can be troublesome or potentially dangerous, such as anticholinergic effects (dry mouth, blurred vision, urinary retention, ileus), sedation, orthostatic hypotension, tachycardia and atrio‐ventricular conduction disturbances. Such adverse effects are likely to reduce the tolerance of this group of drugs in elderly or unwell patients. Some subgroups of patients with painful neuropathy such as diabetes may also have autonomic neuropathy and may not tolerate the orthostatic hypotension associated with tricyclic antidepressants.

With increasing evidence of the efficacy of gabapentin in a wide variety of pain syndromes, especially neuropathic pain, gabapentin may be potentially useful because of its relative freedom from serious adverse effects, its lack of interactions with other drugs and its lack of potential for causing drug dependence.

A comparison of the evidence available of efficacy and toxicity for anticonvulsants (gabapentin, phenytoin and carbemazepine) and antidepressants (tricyclic antidepressants and SSRIs) in patients with diabetic neuropathy and postherpetic neuralgia has recently been made by Collins et al. [129] These two neuropathic pain conditions were chosen according to strict diagnostic criteria. Although two previous systematic reviews of anticonvulsants and antidepressants in diabetic neuropathy showed no significant difference in efficacy or adverse effects between the two drug classes [130, 131], Collins et al. found that when data from randomised controlled trials for both diabetic neuropathy and postherpetic neuralgia were pooled, the NNT for at least 50% pain relief was identical for both classes of drugs. When gabapentin was compared with other anticonvulsants, there was no significant difference in efficacy.

The NNT for gabapentin was 3.4 compared with 2.2 for phenytoin/carbemazepine. The number needed to harm (NNH, defined as the number needed to harm one patient from the therapy) for minor adverse effects was 2.7 for both antidepressants and anticonvulsants. Collins et al. used two trials to provide data on minor adverse effects for gabapentin and two trials for phenytoin. The NNH (minor adverse effects) was 2.6 similar to that of gabapentin and 3.2 for phenytoin. The NNH (major adverse effects) for the tricyclic antidepressants was 17, and no significant difference in the incidence of major adverse effects was found between anticonvulsants and placebo.

Collins et al. suggested that the difference in the incidence of major adverse effects can be compared by using the ratio between treatment specific benefit and treatment specific harm (defined as the number of patients needed to experience at least 50% benefit for one to experience a major adverse effect that warranted discontinuation of treatment). The ratio for gabapentin was 6 compared with an average of 8 for all anticonvulsants, and 6 for all antidepressants. As adverse data were pooled from both diabetic and postherpetic neuralgia studies, methodological factors and heterogenicity in these data may limit the validity and robustness of these ratios. The spectrum of the pain and short study duration tend to underestimate the treatment effect, whereas the small sample size of the studies overestimate the treatment effect.

The above evidence suggests that gabapentin is as efficacious at treating neuropathic pain with no significant difference in minor adverse effects and a low propensity for serious adverse effects compared with other anticonvulsants and antidepressants. Therefore, gabapentin is a useful agent in the multimodal approach in the management of neuropathic pain.

Adverse Reactions in Pooled Placebo-Controlled Trials in Postherpetic Neuralgia

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Postherpetic Neuralgia

The most common adverse reactions associated with the use of NEURONTIN in adults, not seen at an equivalent frequency among placebo-treated patients, were dizziness, somnolence, and peripheral edema.

In the 2 controlled trials in postherpetic neuralgia, 16% of the 336 patients who received NEURONTIN and 9% of the 227 patients who received placebo discontinued treatment because of an adverse reaction. The adverse reactions that most frequently led to withdrawal in NEURONTIN-treated patients were dizziness, somnolence, and nausea.

Following table lists adverse reactions that occurred in at least 1% of NEURONTIN-treated patients with postherpetic neuralgia participating in placebo-controlled trials and that were numerically more frequent in the NEURONTIN group than in the placebo group.

TABLE 3. Adverse Reactions in Pooled Placebo-Controlled Trials in Postherpetic Neuralgia
NEURONTIN
N=336
%		 Placebo
N=227
%
Reported as blurred vision
Body as a Whole
  Asthenia 6 5
  Infection 5 4
  Accidental injury 3 1
Digestive System
  Diarrhea 6 3
  Dry mouth 5 1
  Constipation 4 2
  Nausea 4 3
  Vomiting 3 2
Metabolic and Nutritional Disorders
  Peripheral edema 8 2
  Weight gain 2 0
  Hyperglycemia 1 0
Nervous System
  Dizziness 28 8
  Somnolence 21 5
  Ataxia 3 0
  Abnormal thinking 3 0
  Abnormal gait 2 0
  Incoordination 2 0
Respiratory System
  Pharyngitis 1 0
Special Senses
  Amblyopia 3 1
  Conjunctivitis 1 0
  Diplopia 1 0
  Otitis media 1 0

Other reactions in more than 1% of patients but equally or more frequent in the placebo group included pain, tremor, neuralgia, back pain, dyspepsia, dyspnea, and flu syndrome.

There were no clinically important differences between men and women in the types and incidence of adverse reactions. Because there were few patients whose race was reported as other than white, there are insufficient data to support a statement regarding the distribution of adverse reactions by race.

 

Can I Drive or Ride a Bike After I Take Gabapentin ?

Gabapentin is used with other medications to prevent and control seizures. It is also used to relieve nerve pain following shingles (a painful rash due to herpes zoster infection) in adults.

Gabapentin is known as an anticonvulsant or antiepileptic drug.

You may feel sleepy, tired or dizzy when you first start taking gabapentin. This may also happen if your dose has increased.

If this happens to you, do not drive or ride a bike until you feel better.

It’s an offence to drive a car if your ability to drive safely is affected. It’s your responsibility to decide if it’s safe to drive. If you’re in any doubt, do not drive.

If you have epilepsy, you are generally not allowed to drive until:

    • you have not had any seizures (while awake) for 1 year
    • you have only had seizures while you’re asleep

If you change your epilepsy medicine, your doctor will tell you whether you need to stop driving and for how long.

How and when to take Gabapentin ?

Gabapentin is a prescription medicine. It’s important to take it as advised by your doctor.

Dosage and strength

Each capsule of gabapentin contains 100mg, 300mg or 400mg of gabapentin. Each tablet contains 600mg or 800mg of gabapentin.

If you’re taking gabapentin as a liquid, 2ml is usually the same as taking a 100mg tablet or capsule. Always check the label.

Dosage for epilepsy

The usual dose for:

    • adults and older children (aged 12 and over) is 900mg to 3,600mg a day, split into 3 doses
    • younger children (aged 6 to 12) – varies depending on their weight

Dosage for nerve pain

The usual dose to treat nerve pain in adults is 900mg to 3,600mg a day, split into 3 doses.

Changes to your dose

To prevent side effects, your doctor will prescribe a low dose to start with and then increase it over a few days. Once you find a dose that suits you, it will usually stay the same.

How to take Gabapentin ?

Swallow gabapentin capsules and tablets whole with a drink of water or juice. Do not chew them.

You can take gabapentin with or without food, but it’s best to do the same each day.

Try to space your doses evenly through the day. For example, you could take it first thing in the morning, early afternoon and at bedtime.

If you or your child are taking a liquid, it will come with a plastic syringe or spoon to measure your dose. If you do not have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen spoon, as it will not measure the right amount.

How long to take it for

If you have epilepsy, it’s likely that once your condition is under control you’ll still need to take gabapentin for many years.

If you have nerve pain, once your pain has gone you’ll continue to take gabapentin for several months or longer to stop it coming back.

If you forget to take it

If you forget a dose, take it as soon as you remember. If it’s within 2 hours of the next dose, it’s better to leave out the missed dose and take your next dose as normal.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you have epilepsy, it’s important to take this medicine regularly. Missing doses may trigger a seizure.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

If you take too much

Taking too much gabapentin can cause unpleasant side effects.

Urgent advice: Contact 111 for advice or go to A&E now if:

you take more than your prescribed dose of gabapentin and:

    • you feel dizzy or sleepy
    • you have double vision
    • you start slurring your words
    • you have diarrhoea
    • you pass out (faint)

If you need to go to A&E, take the gabapentin packet or leaflet inside it, plus any remaining medicine, with you.

Stopping gabapentin

It’s important not to stop taking gabapentin suddenly, even if you feel fine. Stopping gabapentin suddenly can cause serious problems.

If you have epilepsy, stopping gabapentin suddenly can cause seizures that will not stop.

If you’re taking it for any reason and stop suddenly, you may have a severe withdrawal syndrome. This can have unpleasant symptoms, including:

    • anxiety
    • difficulty sleeping
    • feeling sick
    • pain
    • sweating

It’s possible to prevent withdrawal seizures and other symptoms by gradually reducing the dose of gabapentin.

Do not stop taking gabapentin without talking to your doctor – you’ll need to reduce your dose gradually.

Risks of Taking Gabapentin During Pregnancy and When Breastfeeding

Risks during pregnancy and when breastfeeding

People who are pregnant and those who intend to become pregnant should tell a doctor before taking gabapentin.

Research from 2020 suggests that taking this drug during pregnancy may be associated with a higher risk of cardiac malformations in the fetus, a condition called small for gestational age, and preterm birth.

However, it is also essential to control seizures during pregnancy, so pregnant people should only take the drug if it is absolutely necessary.

People should never start or stop taking gabapentin for seizure control before talking with a doctor. They will assess the potential risks and benefits.

After childbirth, gabapentin passes into breast milk. At low levels, it may not affect the infant. However, it is best to discuss this issue with a doctor before breastfeeding.

Presence of Other Health Conditions That Affect Gabapentin

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)

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.