Neuropathic pain is pain coming from damaged nerves. It differs from pain messages carried along healthy nerves from damaged tissue (a fall, cut, or arthritic knee). Neuropathic pain is treated by different medicines than pain from damaged tissue. Medicines like paracetamol or ibuprofen are not effective in neuropathic pain, while medicines that are sometimes used to treat depression or epilepsy can be very effective in some people with neuropathic pain. Our understanding of fibromyalgia (a condition of persistent, widespread pain and tenderness, sleep problems, and fatigue) is poor, but fibromyalgia can respond to the same medicines as neuropathic pain.
Gabapentin was developed to treat epilepsy, but it is now used to treat various forms of chronic pain. On 17 March 2014 we performed searches to look for clinical trials where gabapentin was used to treat neuropathic pain or fibromyalgia. We found that 5633 participants had been involved in 37 studies of reasonable quality. They tested gabapentin against placebo for four weeks or more. Studies lasting only one or two weeks are unhelpful when pain can last for years.
Only two conditions had useful amounts of data - postherpetic neuralgia (chronic pain following shingles) and painful diabetic neuropathy (where nerves are damaged in diabetes). Gabapentin helped 3 or 4 people in 10 by reducing their pain by at least half, while with placebo only 2 in 10 had this result.
With gabapentin 6 people in 10 can expect to have some adverse events, including dizziness (2 in 10), somnolence (1 or 2 in 10), peripheral oedema (1 in 10), and gait disturbance (1 in 10). Serious adverse events (1 in 33) were no more common than with placebo. One person in 10 withdrew because of adverse events. Persons taking gabapentin can expect to have at least one adverse event (6 in 10), or stop taking gabapentin because of an adverse event (about 1 in 10).
Gabapentin is helpful for some people with chronic neuropathic pain or fibromyalgia. 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.