Roger Chou, MD
What are the efficacy and safety of gabapentin for chronic neuropathic pain in adults?
Included studies compared gabapentin with placebo, no intervention, or an active comparator in patients ≥ 18 years of age who had ≥ 1 chronic neuropathic pain condition. Outcomes included patient-reported reduction in pain intensity ≥ 50%; patient-reported global impression of clinical change (PGIC) very much improved; Initiative on Methods, Measurement and Pain Assessment in Clinical Trials (IMMPACT) definitions of substantial benefit; and adverse events.
MEDLINE and EMBASE/Excerpta Medica (to Jan 2011); Cochrane Central Register of Controlled Trials (Issue 12, 2010); PhRMA clinical study results database; and reference lists were searched for double-blind, randomized, controlled trials (RCTs). 29 trials (n = 3571) met the selection criteria; 17 had an Oxford quality score of 5 out of 5, 8 had a score of 4, and 4 had scores ≤ 3. Study duration ranged from 10 days to 14 weeks (median 6 wk). 26 RCTs were placebo-controlled, and 6 had an active comparator.
The main results of placebo-controlled trials are in the Table. Meta-analysis showed that the gabapentin group had a higher rate of ≥ 50% pain relief than the placebo group overall (Table), in patients with postherpetic neuralgia (3 RCTs, relative benefit increase [RBI] 67%, 95% CI 29 to 116) and painful diabetic neuropathy (4 RCTs, RBI 78%, CI 43 to 121) but not in those with mixed neuropathic pain (1 RCT, RBI 45%, −12 to 137), nerve injury pain (1 RCT, RBI 44%, CI −35 to 222), or small-fiber sensory neuropathy (1 RCT, RBI 400%, CI −35 to 3765). 6 RCTs compared gabapentin with an active comparator. Gabapentin plus nortriptyline was better for reducing pain intensity than either drug alone (1 RCT, n = 56); amitriptyline was better than gabapentin (n = 38, outcome not specified); and no differences for reducing pain were reported for comparisons of gabapentin and nortriptyline (1 RCT, n = 76), tramadol (1 RCT, n = 18), morphine (1 RCT, n = 57), or amitriptyline (1 RCT, n = 25).
In adults with chronic neuropathic pain, gabapentin reduces pain but increases adverse events. Evidence is insufficient to evaluate the efficacy of gabapentin compared with other drugs.
Gabapentin vs placebo in chronic neuropathic pain*
*IMMPACT = Initiative on Methods, Measurement and Pain Assessment in Clinical Trials; PGIC = Patient Global Impression of Change; other abbreviations defined in Glossary. RBI, RRI, NNT, NNH, and CI calculated from control event rates, relative risks, and risk differences in article.
Chou R. Review: Gabapentin reduces some types of chronic neuropathic pain more than placebo in adults. Ann Intern Med. ;155:JC1–8. doi: 10.7326/0003-4819-155-2-201107190-02008
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Published: Ann Intern Med. 2011;155(2):JC1-8.
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