Gabapentin Side Effects – Overview
Gabapentin is a well-established anticonvulsant drug that reduces abnormal excitement in the nerve cells in the brain. As a result, gabapentin effectively treats seizures in people with epilepsy and is used to relieve the pain of post-herpetic neuralgia (pain in the skin areas affected by shingles). (1, 2)
Gabapentin enacarbil, as an extended-release tablet, is approved for the treatment of moderate-to-severe primary Restless Legs Syndrome (RLS). (2, 3)
Like any other drug, gabapentin may cause side effects fully described in the Medication Guide. However, some of them, such as hypersensitivity or suicidal thoughts, although rare, can be life-threatening and even fatal. Recognizing the signs of life-threatening side effects can save your life. (1, 3)
This article explains the most common and serious side effects. Keep reading to learn about when you need to call your doctor and why shouldn’t you stop taking gabapentin on your own when treating epilepsy.
What are Gabapentin’s Possible Side Effects?
Gabapentin’s Possible Side Effects
The most common side effects of gabapentin reported while studied were:
- fever;
- viral infection;
- nausea and vomiting;
- feeling tired;
- feeling drowsy;
- difficulty with speaking;
- movement problems: lack of coordination, difficulty with coordination, tremor, jerky movements;
- eye problems: double vision, unusual eye movement. (1)
Headache, sleepiness, and dizziness are the most common side effects (>10%, at least twice than placebo) of gabapentin’s extended-release formulation. Nausea, dry mouth, fatigue, irritability, feeling abnormal, vertigo, or depression are side effects that may occur in less than 10% of the patients. (3)
In some cases, following the United Kingdom National Health Service recommendations, you may help yourself: (4)
Nausea and vomiting – Avoid rich or spicy food, and take gabapentin with or after a meal. Taking small sips of fluids to keep you hydrated. Don’t use drugs to treat vomiting without consulting your doctor.
Diarrhea – As a consequence of diarrhea, you can dehydrate. You can notice if you pee less, have dark urine, or it has a strong smell. Drink plenty of water or other liquids to avoid it.
Dry mouth – Use sugar-free chewing gum or sweets.
Headache – Usually, the headache is gone a week after the treatment is initiated. Drink water or other fluids and rest. However, tell your doctor if you have severe headaches or they last more than a week. (4)
Blurred vision – Avoid driving, biking, or using machines or tools. Tell your doctor if it does not go away in a couple of days. (4)
Tell your doctor if these or other adverse events appear, bother you, and don’t go away. Your doctor will give you appropriate medical advice.
Warning and Precautions When Using Gabapentin
Some side effects require precautions because they are severe, life-threatening, or even fatal. (1, 3)
Multiorgan hypersensitivity is a rare side effect caused by some medications, such as gabapentin, lamotrigine, or carbamazepine, ranging from 1 to 10 in 10,000. Known also as Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), it affects several organs simultaneously and can be life-threatening or even fatal, so early signs detection is crucial. (1, 3, 5)
Fever, rash, and/or swollen, painful, or tender lymph glands in the neck, armpit, or groin (lymphadenopathy) are typical symptoms. It involves the liver, kidney, or heart, which can cause yellow eyes or skin, bruising, unusual bleeding, feeling weak or pain in muscles, and inflammation of the kidney and heart muscle. An increased level of white blood cells than normal (eosinophilia) is often present. (1, 3, 6)
Fever or lymphadenopathy appears first, so if you have it, even without a rash, call your doctor immediately. If there is no other cause for these symptoms, your doctor will discontinue gabapentin. (1, 3)
Anaphylaxis and Angioedema – Gabapentin can cause serious and life-threatening allergic reactions that can appear at any time. Difficult breathing, trouble swallowing due to swollen lips, throat, and tongue, or decreased blood pressure are signs that require immediate medical care. If you notice any of the symptoms mentioned above, stop taking your drug and seek urgent medical care. (1,3)
Suicidal thoughts – are associated with antiepileptic drugs and may happen in 1 in 500 patients on treatment. Some patients may feel sad, nervous, or restless and can easily get upset, have suicidal thoughts, or attempt to commit suicide. Depression can also occur or, if present, worsen. Panic attacks, aggressive behavior, anger or violence, and an extreme increase in activity and talking are other symptoms. (1,3)
Your doctor will monitor you; however, you can also pay attention to sudden changes in mood, behaviors, thoughts, or feelings. Keep regularly all scheduled visits and tell your doctor any changes you notice.
Suicidal thoughts can be associated with your medication, but other reasons can cause them too. So, talk to your doctor first before you stop taking your medication. (1,3)
Changes in behavior and thinking in children – In children 3 to 12 years of age, gabapentin can be associated with aggressive behavior, hyperactivity, emotional changes, problems with concentration, or changes in school performance. Carefully monitor how your child reacts to the therapy and pay attention if such events occur. Talk to the doctor and ask for medical advice. (1,3)
Driving Impairment, Somnolence/Sedation, and Dizziness – At the beginning of gabapentin treatment, you may experience clumsiness, vision changes, dizziness, unsteadiness, sleepiness, or problems with thinking. In controlled epilepsy trials, 19% of the patients reported somnolence and 17% dizziness. Those who had post-herpetic neuralgia reported the same symptoms at a higher rate. (1, 3)
It is unknown how long this condition can last, so don’t drive until you find out how you react to the medication and if you can drive or operate heavy machinery. Consult your doctor if these symptoms bother you and limit your daily life. If needed, your doctor may discontinue gabapentin therapy. (1, 3, 6)
Increased seizure frequency may occur if gabapentin is abruptly discontinued in patients with seizure disorders. It may worsen your epilepsy and cause seizures that will not stop (status epilepticus). Different studies reported that the incidence of status epilepticus was not higher than 1.5%; however, the data is insufficient to estimate the frequency. In case you notice increased seizure frequency, talk to your doctor. (1,3)
Call your doctor for medical advice about any adverse event that appears. In addition, you may report side effects to FDA at 1-800-FDA-1088.
Other Advice You Should Know About Gabapentin
When using gabapentin, keep in mind the following:
Gabapentin usage with morphine – gabapentin interacts with morphine, where morphine increases gabapentin concentration. Respiratory depression visible with the pale or blue mouth, fingernails, or skin and irregular breathing are the signs of the interaction. If it happens to you, check with your doctor about what to do.
Pregnancy and breastfeeding – no data is available to say if gabapentin harms the fetus. If you plan to become pregnant, talk to your doctor so the doctor can decide the most appropriate treatment option for you. Gabapentin passes into the milk, so it should be considered how to feed your baby while on therapy.
Talk to your doctor – If you have diabetes, kidney problems, go on hemodialysis, or suffer from depression and mood and behavior problems, tell your doctor. Also, tell your doctor about the medication that you already take.
Don’t drink alcohol – avoid alcohol or use preparations that cause dizziness or make you sleepy. Such consumption may worsen your sleepiness and dizziness.
If you took more than the dose your doctor prescribed, you might get overdosed. In such a case, the following symptoms may appear: double vision, slurred speech, drowsiness, and diarrhea. If it happens to you, call the poison control helpline at 1-800-222-1222. The information is also available online at https://www.poisonhelp.org/help. In case of seizure or trouble with breathing, call 911 immediately. (1-3)
Gabapentin Misuse and Abuse Can Be Fatal
After 20 years of usage, some studies have shown gabapentin abuse or misuse. It happened for recreational purposes in combination with opioids, benzodiazepines, or psychedelics, as self-medication, or used in higher doses than recommended in those with prescription. (7) Gabapentin abuse can lead to substance dependence and intoxication. (8)
In such cases, withdrawal symptoms like anxiety, agitation, fatigue, restlessness, dizziness, sensitivity to light, sweating, irregular heartbeat, or others may occur. (9)
Gabapentin abuse or misuse can be fatal. According to the Centers for Disease Control and Prevention, in 2019-20, half (52.3%) of gabapentin-involved deaths were due to overdose. The overdose death rate from the illegal use of opioids with gabapentin raised to 69.2% in the last quarter of 2020. (10)
Gabapentin’s Recommended Dosage
Gabapentin’s daily dosage depends on the disease and the patient’s age. This drug is available as an oral solution (50 mg/ml), capsules (100 mg, 300 mg, and 400 mg), or tablets (600 mg and 800 mg) that make the dose titration easy.
Epilepsy with Partial Onset Seizures – The starting daily dose in patients 12 years of age and older is 900 mg, divided into three doses. The daily dose can be increased by up to 1.800 mg/daily.
In patients 3 to 11 years of age, the starting daily dose is 10 to 15 mg/kg/day, divided into three equal doses. The dose increase depends on the age, so the recommended dose can be up to 40 mg/kg/day, given in three divided doses, and can be achieved in 3 days increasing step by step. (1,3)
Postherpetic Neuralgia – The initial dose of gabapentin is 300 mg as a single dose and can be increased to 1.800 mg/day by adding 300 mg daily, day by day. Your doctor will divide the daily dose into 2 or 3 single doses. (1) If your doctor prescribes an extended-release formulation, you will take gabapentin twice daily. (3)
RLS treatment – the recommended dose is 600 mg once daily and should be taken every day at 5 p.m. If you miss the dose, wait till the next day at the same time to take the next dose. (3)
Take note that you cannot interchange extended-release formulation with other gabapentin products. (3) Any therapy change should be done by your healthcare provider.
Final Thoughts
Gabapentin is a well-established medication for epilepsy treatment, for pain relief in post-herpetic neuralgia or RLS. When taken as recommended, gabapentin has an acceptable safety profile with well-known side effects.
Take your gabapentin dose as recommended, and be aware of the possible side effects that might appear. Even if some adverse events look mild, talk to your doctor and report it to FDA.
If anaphylaxis, multi-organ hypersensitivity, or suicidal thoughts symptoms occur, the treatment should be discontinued. In such cases, call your doctor right away to get advice on what to do.
Gabapentin can effectively help you to control seizures, relieve pain, or release from RLS. Use it as recommended to treat your disease safely.
References:
- FDA Food and Drug Administration, NEURONTIN (gabapentin), Prescribing Information and Medication Guide, 2017 Oct, https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020235s064_020882s047_021129s046lbl.pdf
- MedlinePlus, Gabapentin, 2020 May, https://medlineplus.gov/druginfo/meds/a694007.html
- FDA Food and Drug Administration, HORIZANT (gabapentin enacarbil) extended-release tablets, Prescribing Information and Medication Guide, 2012 Jun, https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/022399s003lbl.pdf
- NHS National Health Service, Side effects of gabapentin, 2022 Jan, https://www.nhs.uk/medicines/gabapentin/side-effects-of-gabapentin/
- NIH National Library of Medicine, Natasha Klimas, BS, Josephine Quintanilla-Dieck, MD, and Travis Vandergriff, MD, Drug-Induced Delayed Multi-organ Hypersensitivity Syndrome, Cutaneous Drug Eruptions, 2015 May https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7122205/#:~:text=Introduction-,Drug%2Dinduced%20delayed%20multi%2Dorgan%20hypersensitivity%20syndrome%20(DIDMOHS),hematologic%20abnormalities%20and%20visceral%20manifestations.
- Mayo Clinic, Gabapentin (oral route), 2022 Nov, https://www.mayoclinic.org/drugs-supplements/gabapentin-oral-route/precautions/drg-20064011
- Smith, R., Havens, J., and Walsh, S., Gabapentin misuse, abuse, and diversion: A systematic review. Addiction, 2016 Jul, 111(7), 1160-1174. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5573873/
- Hägg S., Jönsson A., and Ahlner J., Current Evidence on Abuse and Misuse of Gabapentinoids, Drug Safety, 2020, 43:1235–1254 https://link.springer.com/content/pdf/10.1007/s40264-020-00985-6.pdf?pdf=button
- Hellwig, T.R., Hammerquist, R. & Termaat, J. (2010). Withdrawal symptoms after Gabapentin discontinuation. American Journal of Health-System Pharmacy, 67(11), 910-912. https://academic.oup.com/ajhp/article-abstract/67/11/910/5130783
- Centers for Disease Control and Prevention, Morbidity and Mortality Weekly Report (MMWR), 2022 May https://www.cdc.gov/mmwr/volumes/71/wr/mm7119a3.htm
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