Dose-response for analgesic effect of amitriptyline in chronic pain

A randomised, double-blind, multiple dose, crossover study with three 3-week treatment periods was set up to compare the analgesic efficacy and adverse effects of amitriptyline in oral doses of 25, 50 or 75 mg. Patients used diaries to assess their pain, and clinic assessments were made at the end of each treatment period. It was found that in 29 patients with chronic (more than 2 months) pain, amitriptyline 75 mg provided significantly greater efficacy than amitriptyline 25 or 50 mg. There was no significant difference in mood scores between the different doses of amitriptyline, but sleep was judged significantly better with 75 mg compared with 25 mg. The incidence of adverse effects was significantly higher with the 75 mg dose, and the principal adverse effects were dry mouth and drowsiness. In the context of chronic pain, the analgesic effect of amitriptyline was shown to have a dose-response unrelated to mood elevation, but there was a dose-response for the incidence of adverse effects.