Clearly beneficial
4-14 ANTIDEPRESSANTS AND CHRONIC PAIN
Antidepressants are used widely to treat symptoms other than depression, many of which fit into the general category of pain. These include neuropathic pain (postherpetic neuralgia, diabetic neuropathy), irritable bowel syndrome, temporomandibular joint dysfunction, atypical facial pain, and fibromyalgia. Do they work?
"There is strong evidence that tricyclic antidepressants are effective for several of these conditions. For established postherpetic neuralgia tricyclic anti-depressants seem to be the only drugs of proved benefit." (Two patients in 5 achieve at least a 50% relief of pain.) All individual randomized trials of diabetic neuropathy and post herpetic neuralgia showed active treatment to be better than placebo. Two studies of atypical facial pain and pain after stroke also reported at least 50% pain relief in 2 to 3 of every 5 treated.
Amitriptyline (Elavil) has proved analgesic efficacy with a median preferred dose of 75 mg. The speed of onset (1 to 7 days) is much faster than that reported in depression. The analgesic effect is distinct from any effect on mood.
Two rules in managing chronic pain with antidepressants: 1) When pain relief with conventional analgesics (aspirin to morphine) is inadequate, and 2) When pain relief from conventional analgesics is combined with intolerable or unmanageable adverse effects. The failure of conventional analgesics should justify a therapeutic trial of antidepressants, particularly if the pain is neuropathic (pain in a numb area).
A secondary role is their use in addition to conventional analgesics. This can be particularly effective in patients with cancer who have pain at multiple sites, some nocioceptive and some neuropathic. Improved sleep is a huge bonus.
There is little evidence that one antidepressant is better than another, though some patients troubled by adverse effects may benefit from changing drugs. A common first choice is amitriptyline starting with 25 mg at bedtime. The editorialists advise patients to increase the dose by 25 mg at weekly intervals until they achieve pain relief or adverse effects become problematic. Maximum dose 150 mg. "It is clear that antidepressants have an important role to play in relieving chronic pain."
BMJ March 15, 1997; 314: 763-64 Editorial from Univ. Of Oxford, Oxford, UK

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