Antidepressants and pain: a review of the pharmacological data supporting the use of certain tricyclics in chronic pain.

There have been reports that tricyclic antidepressants, such as clomipramine (Anafranil), alleviate some forms of chronic pain in man. This paper examines and compares the pharmacological properties of centrally-acting analgesics and the tricyclic antidepressants, to establish a scientific basis for the observed clinical effects of the tricyclics. Opiates and tricyclic antidepressants share a number of pharmacological properties including activity in animal tests for antidepressant and analgesic activity. In doses which alone were not analgesic, clomipramine potentiated whilst maprotiline (Ludiomil) attenuated the analgesic activity of single doses of morphine in laboratory animals. However, when morphine and tricyclic agent were given repeatedly over several days, clomipramine enhanced or accelerated the onset of morphine tolerance, whereas maprotiline delayed tolerance. It is concluded that there is much experimental data to support the belief that tricyclics such as clomipramine may be useful in chronic clinical pain. Where an opiate is being administered chronically (for example in terminal pain) the concomitant administration of maprotiline may delay onset of tolerance.