Effective analgesia in neuropathic pain and other syndromes

Antidepressants are used widely to treat symptoms other than depression, many of which fit into a general category of pain. They include neuropathic pain (postherpetic neuralgia, diabetic neuropathy (p 827)1), irritable bowel syndrome, temporomandibular joint dysfunction, atypical facial pain, and fibromyalgia. In Britain no antidepressant is licensed for these indications. Do they work?

There is strong evidence from systematic reviews of randomised trials that tricyclic antidepressants are effective treatments for several of these conditions.2 3 4 For established postherpetic neuralgia, tricyclic antidepressants seem to be the only drugs of proved benefit,4 and the number needed to treat to achieve at least 50% pain relief after three to six weeks compared with placebo was 2.3 (95% confidence interval 1.7 to 3.3).2 This means that two patients in five will achieve this (high) level of relief who would not have done so with placebo. Numbers needed to treat of two to three compare well with the most effective analgesics in acute pain, and with anticonvulsants in neuropathic pain.5

Figure 1 shows results from individual randomised trials of diabetic neuropathy and postherpetic neuralgia, each point representing one randomised trial.2 All …