Gabapentin for chronic neuropathic pain and fibromyalgia in adults
Abstract
Background
This review updates parts of two earlier Cochrane reviews investigating effects of gabapentin in chronic neuropathic pain (pain due to nerve damage). Antiepileptic drugs are used to manage pain, predominantly for chronic neuropathic pain, especially when the pain is lancinating or burning.
Objectives
To evaluate the analgesic effectiveness and adverse effects of gabapentin for chronic neuropathic pain management.
Search methods
We identified randomised trials of gabapentin in acute, chronic or cancer pain from MEDLINE, EMBASE, and CENTRAL. We obtained clinical trial reports and synopses of published and unpublished studies from Internet sources. The date of the most recent search was January 2011.
Selection criteria
Randomised, double‐blind studies reporting the analgesic and adverse effects of gabapentin in neuropathic pain with assessment of pain intensity and/or pain relief, using validated scales. Participants were adults aged 18 and over.
Data collection and analysis
Two review authors independently extracted data. We calculated numbers needed to treat to benefit (NNTs), concentrating on IMMPACT (Initiative on Methods, Measurement and Pain Assessment in Clinical Trials) definitions of at least moderate and substantial benefit, and to harm (NNH) for adverse effects and withdrawal. Meta‐analysis was undertaken using a fixed‐effect model.
Main results
Twenty‐nine studies (3571 participants), studied gabapentin at daily doses of 1200 mg or more in 12 chronic pain conditions; 78% of participants were in studies of postherpetic neuralgia, painful diabetic neuropathy or mixed neuropathic pain. Using the IMMPACT definition of at least moderate benefit, gabapentin was superior to placebo in 14 studies with 2831 participants, 43% improving with gabapentin and 26% with placebo; the NNT was 5.8 (4.8 to 7.2). Using the IMMPACT definition of substantial benefit, gabapentin was superior to placebo in 13 studies with 2627 participants, 31% improving with gabapentin and 17% with placebo; the NNT was 6.8 (5.6 to 8.7). These estimates of efficacy are more conservative than those reported in a previous review. Data from few studies and participants were available for other painful conditions.
Adverse events occurred significantly more often with gabapentin. Persons taking gabapentin can expect to have at least one adverse event (66%), withdraw because of an adverse event (12%), suffer dizziness (21%), somnolence (16%), peripheral oedema (8%), and gait disturbance (9%). Serious adverse events (4%) were no more common than with placebo.
There were insufficient data for comparisons with other active treatments.
Authors' conclusions
Gabapentin provides pain relief of a high level in about a third of people who take if for painful neuropathic pain. Adverse events are frequent, but mostly tolerable. More conservative estimates of efficacy resulted from using better definitions of efficacy outcome at higher, clinically important, levels, combined with a considerable increase in the numbers of studies and participants available for analysis.
PICOs
Plain language summary
Gabapentin for chronic neuropathic pain and fibromyalgia in adults
Antiepileptic drugs like gabapentin are commonly used for treating neuropathic pain, usually defined as pain due to damage to nerves. This would include postherpetic neuralgia (persistent pain experienced in an area previously affected by shingles), painful complications of diabetes, nerve injury pain, phantom limb pain, fibromyalgia and trigeminal neuralgia. This type of pain can be severe and long‐lasting, is associated with lack of sleep, fatigue, and depression, and a reduced quality of life. In people with these conditions, gabapentin is associated with a moderate benefit (equivalent to at least 30% pain relief) in almost one in two patients (43%), and a substantial benefit (equivalent to at least 50% pain relief) in almost one in three (31%). Over half of those taking gabapentin for neuropathic pain will not have good pain relief, in common with most chronic pain conditions. Adverse events are experienced by about two‐thirds of people taking gabapentin, mainly dizziness, somnolence (sleepiness), oedema (swelling), and gait disturbance, but only about 1 in 10 (11%) have to stop the treatment because of these unpleasant side effects. Overall gabapentin provides pain relief of a high level in about a third of people who take it for painful neuropathic pain. Adverse events are frequent, but mostly tolerable. This review looked at evidence from 29 studies involving 3571 participants.
