To determine the relative efficacy and adverse effects of
antidepressants and
anticonvulsants in the treatment of diabetic neuroapathy and
postherpetic neuralgia, published reports were identified from a variety of electronic databases, including Medline, EMBASE, the Cochrane Library and the Oxford
Pain Relief Database, and from two previously published reviews. Additional studies were identified from the reference lists of retrieved reports. The relative benefit (RB) and number-needed-to-treat (NNT) for one patient to achieve at least 50 %
pain relief was calculated from available dichotomous data, as was the relative risk (RR) and number-needed-to-harm (NH) for minor adverse effects and
drug related study withdrawal. In
diabetic neuropathy, 16 reports compared
antidepressants with placebo (491 patient episodes) and three compared
anticonvulsants with placebo (321). The NNT for at least 50 %
pain relief with
antidepressants was 3.4 (95 % confidence interval 2.6-4. 7) and with
anticonvulsants 2. 7 (2. 2-3. 8). In
postherpetic neuralgia, three reports compared
antidepressants with placebo (145 patient episodes) and one compared
anticonvulsants with placebo (225), giving an NNT with
antidepressants of 2.1 (1. 7-3) and with
anticonvulsants 3.2 (2.4-5). There was little difference in the incidence of minor adverse effects with either
antidepressants or
anticonvulsants compared with placebo, with 1VH (minor) values of about 3. For
drug-related study withdrawal,
antidepressants had an NNH (major) of 17 (11-43) compared with placebo, whereas with
anticonvulsants there was no significant difference from placebo.
Antidepressants and
anticonvulsants had the same efficacy and incidence of minor adverse effects in these tzoo
neuropathic pain conditions. There was no evidence that
selective serotonin reuptake inhibitors (
SSRIs) were better than older
antidepressants, and no evidence that
gabapentin was better than older
anticonvulsants. In these trials patients were more likely to stop taking
antidepressants than
anticonvulsants because of adverse effects.