Conditions in which antidepressants have been used include diabetic neuropathy, postherpetic neuralgia, headaches, arthritis, chronic back pain, cancer, thalamic pain, facial pain, and phantom limb pain. Although much of the available information is derived from inadequately controlled trials, it seems that antidepressants provide analgesia in many of these disorders. The analgesic effects tend to be independent of antidepressant effects, and doses of heterocyclic antidepressants used for analgesia seem to be lower than those considered effective in the treatment of depression. Doses should be started low and gradually increased until the patient reaches the highest tolerable dose. Onset of analgesia is variable, ranging from 1 day to 10 weeks. Common side effects include dry mouth, drowsiness, urinary retention, orthostatic hypotension, and constipation. Optimum dosages and schedules have not been established.