Gabapentin Side Effects: Brand name Neurontin. Dosage forms: 100mg, 300mg, 400mg, 600mg and 800mg capsules and 50/ml liquid. Gabapentin was initially introduced as an anticonvulsant, and continues to be used in a limited way for its anticonvulsant effects. Today the primary use of gabapentin is of management of neuropathic pain. Specific neuropathic pain syndromes that are often effectively treated with gabapentin include diabetic peripheral neuropathy, other peripheral neuropathies, post-herpetic neuropathy, tic-de-la-rue and other mononeuropathies, and radicular neuropathic pain from cervical and lumbosacral nerve root irritation. Almost every chronic pain syndrome is at times treated with gabapentin. The biggest problem with treating painful conditions with gabapentin is the sedating gabapentin side effect. This sedation makes it necessary to gradually increase the dosing of gabapentin and so it can take weeks to get up to an effective dose of gabapentin. This combined with the unpredictable efficacy of gabapentin for its pain alleviation make it often difficult for patients to stay with the course long enough to get optimal benefit.

Black Box Warning: Gabapentin has no black box warnings.

Common Gabapentin Side Effects: The most common side effect of gabapentin as mentioned above is sedation. This is also described as somnolence and fatigue in some documentation. Weight gain is fairly common as a gabapentin side effect with long term use. This can be insidious or dramatic. When insidious it may not be apparent to the individual affected that their slow, ongoing weight gain is related to the gabapentin. Many other gabapentin side effects are likely related to its neurologic effects and include ataxia, nystagmus, tremors, emotional lability in children who use gabapentin, abnormal thinking, dysarthria and accidental injury. Gastrointestinal gabapentin side effects can include nausea, vomiting, diarrhea, constipation, and dyspepsia. Other anticholinergic gabapentin side effects can include the afformentioned sedation and dry mouth. Fever in children using gabapentin is fairly common. Peripheral edema, blurred vision, headache, and runny nose are among other common gabapentin side effects.

Serious Gabapentin Side Effects: The serious gabapentin side effects include hematologic problems including leukopenia and thrombocytopenia. Serious dermatologic gabapentin side effects include Stevens-Johnson Syndrome and erythema multiforme. Suicidal ideation and suicide are possible serious gabapentin side effects. Abrupt withdrawal of gabapentin in patients with seizure disorder can result in seizures, and a withdrawal syndrome can result with abrupt discontinuation of higher doses. Status epilepticus is a possible side effect of gabapentin likely related to abrupt discontinuation.

Gabapentin Side Effects Specific to Children: Some gabapentin side effects are noted in children but not adults. These can include hostility, viral infection, fever, and excessive movement and fidgetiness called hyperkinesia. Acute renal failure has been described as a gabapentin side effect.

Unusual Gabapentin Side Effects: The childhood-specific side effects listed above are probably the most unusul gabapentin side effects.

Drug Interactions: Probably the most important drug interaction with gabapentin is the caution to avoid use with ginko balboa, a commonly used over the counter herbal supplement. The combination can reduce the anticonvulsant efficacy, and high dose ginko use may lead to seizures. Many of the drug interactions with gabapentin are related to additive sedation, and includes most of the opioids, benzodiazapines, antihistamines, barbiturates, tricyclic antidepressants, and other anticonvulsants. Many herbal medications may reduce the efficacy of gabapentin. Marijuana and other canibinoids as well as alcohol can increase the central nervous system sedation of gabapentin. The list of potential drug interactions is extensive, and see the manufacturers prescribing information for more details.

Pregnancy and Lactation Class: Gabapentin is pregnancy category C, and is felt to be probably safe to use during breast feeding.

Special Considerations: Gabapentin is a useful and often effective drug for treatment of both seizure disorders and neuropathic pain syndromes. The sedation and other gabapentin side effects make it very important to use extreme caution when driving or operating potentially dangerous equipment while taking gabapentin.  Many of these side effects can be minimized by a very slow and gradual taper up in the gabapentin dosage.

Lyrica, a newer closely related anticonvulsant to gabapentin, has some advantages over gabapentin because it has lower incidence of some of the most common gabapentin side effects. Lyrica has the advantage of allowing patients to start on a Lyrica dose with a much higher chance of being effective than the very low dose of gabapentin that is tolerated by most patients.  This allows much faster pain relief, a major advantage in some conditions like herpes zoster neuralgia and trigeminal neuralgia. On the other hand for chronic conditions like diabetic peripheral neuropathy and idiopathic peripheral neuropathy starting slowly with gabapentin and gradually titration upward of the gabapentin dose until symptoms are relieved is a viable and less expensive option.


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