Gabapentin is the generic name of a prescription drug used to treat epilepsy. Gabapentin works by decreasing abnormal excitement in the brain.
It also may change the way the body senses pain. Gabapentin is in a class of medications called anticonvulsants.
The U.S. Food and Drug Administration (FDA) approved gabapentin in 1993 under the brand name Neurontin for the drug manufacturer Pfizer. The medication comes in capsule form, as a regular or extended-release tablet, and as a liquid.
Gabapentin interacts with voltage-sensitive calcium channels in cortical neurons. Gabapentin increases the synaptic concentration of GABA, enhances GABA responses at non-synaptic sites in neuronal tissues, and reduces the release of mono-amine neurotransmitters.
One of the mechanisms implicated in this effect of gabapentin is the reduction of the axon excitability measured as an amplitude change of the presynaptic fibre volley (FV) in the CA1 area of the hippocampus.
This is mediated through its binding to presynaptic NMDA receptors.
Other studies have shown that the antihyperalgesic and antiallodynic effects of gabapentin are mediated by the descending noradrenergic system, resulting in the activation of spinal alpha-2 adrenergic receptors. Gabapentin has also been shown to bind and activate the adenosine A1 receptor.
Gabapentin may help to control your condition but will not cure it. Continue to take gabapentin even if you feel well. Do not stop taking gabapentin without talking to your doctor, even if you experience side effects such as unusual changes in behavior or mood.
If you suddenly stop taking gabapentin tablets, capsules, or oral solution, you may experience withdrawal symptoms such as anxiety, difficulty falling asleep or staying asleep, nausea, pain, and sweating. If you are taking gabapentin to treat seizures and you suddenly stop taking the medication, you may experience seizures more often.
Your doctor may decrease your dose gradually over at least a week.
There is moderate-quality evidence that oral gabapentin at doses of 1200 mg daily or more has an important effect on pain in some people with moderate or severe neuropathic pain after shingles or due to diabetes.
Neuropathic pain comes from damaged nerves. It is different from pain messages that are carried along healthy nerves from damaged tissue (for example, from a fall or cut, or arthritic knee). Neuropathic pain is often treated by different medicines (drugs) to those used for pain from damaged tissue, which we often think of as painkillers. Medicines that are sometimes used to treat depression or epilepsy can be effective in some people with neuropathic pain. One of these is gabapentin. Our definition of a good result was someone with a high level of pain relief and able to keep taking the medicine without side effects making them stop.
In January 2017 we searched for clinical trials in which gabapentin was used to treat neuropathic pain in adults. We found 37 studies that satisfied the inclusion criteria, randomising 5914 participants to treatment with gabapentin, placebo, or other drugs. Studies lasted 4 to 12 weeks. Most studies reported beneficial outcomes that people with neuropathic pain think are important. Results were mainly in pain after shingles and pain resulting from nerve damage in diabetes.
In pain after shingles, 3 in 10 people had pain reduced by half or more with gabapentin and 2 in 10 with placebo. Pain was reduced by a third or more for 5 in 10 with gabapentin and 3 in 10 with placebo. In pain caused by diabetes, 4 in 10 people had pain reduced by half or more with gabapentin and 2 in 10 with placebo. Pain was reduced by a third or more for 5 in 10 with gabapentin and 4 in 10 with placebo. There was no reliable evidence for any other type of neuropathic pain.
Side effects were more common with gabapentin (6 in 10) than with placebo (5 in 10). Dizziness, sleepiness, water retention, and problems with walking each occurred in about 1 in 10 people who took gabapentin. Serious side effects were uncommon, and not different between gabapentin and placebo. Slightly more people taking gabapentin stopped taking it because of side effects.
Gabapentin is helpful for some people with chronic neuropathic pain. It is not possible to know beforehand who will benefit and who will not. Current knowledge suggests that a short trial is the best way of telling.
Quality of the evidence
The evidence was mostly of moderate quality. This means that the research provides a good indication of the likely effect. The likelihood that the effect will be substantially different is moderate.