Gabapentin, sold under the brand name Neurontin among others, is an anticonvulsant medication primarily used to treat partial seizures and neuropathic pain. It is commonly used medication for the treatment of neuropathic pain caused by diabetic neuropathy, postherpetic neuralgia, and central pain. It is moderately effective: about 30–40% of those given gabapentin for diabetic neuropathy or postherpetic neuralgia have a meaningful benefit.
Sleepiness and dizziness are the most common side effects. Serious side effects include an increased risk of suicide, respiratory depression, and allergic reactions. Lower doses are recommended in those with kidney disease. Gabapentin acts by decreasing activity of a subset of calcium channels.
Gabapentin was first approved for use in 1993. It has been available as a generic medication in the United States since 2004. In 2020, it was the tenth most commonly prescribed medication in the United States, with more than 49million prescriptions. During the 1990s, Parke-Davis, a subsidiary of Pfizer, used a number of illegal techniques to encourage physicians in the United States to prescribe gabapentin for unapproved uses. They have paid out millions of dollars to settle lawsuits regarding these activities.
Medical uses
Gabapentin is recommended for use in focal seizures and neuropathic pain. Gabapentin is widely prescribed off-label in the US and UK, for example, for the treatment of non-neuropathic pain, anxiety disorders and bipolar disorder. There is concern regarding gabapentin's off-label use due to the lack of strong scientific evidence for its efficacy in multiple conditions and its proven side effects.
Seizures
Gabapentin is approved for the treatment of focal seizures; however, it is not effective for generalized epilepsy.
Neuropathic pain
Gabapentin is recommended as a first-line treatment for chronic neuropathic pain by various medical authorities. This is a general recommendation applicable to all neuropathic pain syndromes except for trigeminal neuralgia, where it may be used as a second- or third-line agent.
In regard to the specific diagnoses, a systematic review has found evidence for gabapentin to provide pain relief for some patients with postherpetic neuralgia and diabetic neuropathy. Gabapentin is approved for the former indication in the US. In addition to these two neuropathies, European Federation of Neurological Societies guideline notes gabapentin effectiveness for central pain. A combination of gabapentin with an opioid or nortriptyline may work better than either drug alone.
Gabapentin shows substantial benefit (at least 50% pain relief or a patient global impression of change (PGIC) "very much improved") for neuropathic pain (postherpetic neuralgia or peripheral diabetic neuropathy) in 30–40% of subjects treated as compared to those treated with placebo.
Evidence finds little or no benefit and significant risk in those with chronic low back pain or sciatica. Gabapentin is not effective in HIV-associated sensory neuropathy and neuropathic pain due to cancer.
Anxiety
There is a small amount of research on the use of gabapentin for the treatment of anxiety disorders.
Gabapentin is effective for the long-term treatment of social anxiety disorder and in reducing preoperative anxiety.
In a controlled trial of breast cancer survivors with anxiety, and in a trial for social phobia, gabapentin significantly reduced anxiety levels.
For panic disorder, gabapentin has produced mixed results.
Sleep
Gabapentin is effective in treating sleep disorders such as insomnia and restless legs syndrome that are the result of an underlying illness, but comes with some risk of discontinuation and withdrawal symptoms after prolonged use at higher doses.
Gabapentin enhances slow-wave sleep in patients with primary insomnia. It also improves sleep quality by elevating sleep efficiency and decreasing spontaneous arousal.
Drug dependence
Gabapentin is moderately effective in reducing the symptoms of alcohol withdrawal and associated craving. The evidence in favor of gabapentin is weak in the treatment of alcoholism: it does not contribute to the achievement of abstinence, and the data on the relapse of heavy drinking and percent of days abstinent do not robustly favor gabapentin; it only decreases the percent days of heavy drinking.