[Clinical and pharmacologic aspects of the analgesic effect of tricyclic antidepressants].

Although tricyclic antidepressants have now been used for more than 20 years in the treatment of chronic pain, controlled studies of their effectiveness are quite recent. The best results are obtained in pain due to peripheral nerve lesions, and high doses are recommended. In contrast with the slow onset of their effect on depression, these drugs promptly relieve pain, which suggests two different mechanisms of action. The analgesic mechanism is unknown; some data indicate that serotonin is involved but an action on the adrenergic system cannot be ruled out. The arguments supporting the recent endorphin hypothesis are reviewed, ad a possible relationship between tricyclic antidepressants and endorphins is envisaged.