Amitriptyline plasma-concentration and clinical effect. A World Health Organisation Collaborative Study.

54 patients in five centres participated in a study of the relationship between steady-state plasma-levels of amitriptyline (AT) and its active metabolite nortriptyline (NT) and therapeutic response. The participants were inpatients who, after a 7-12 day period of assessment, were rated greater than or equal to 16 on the Hamilton rating scale for depression. They were given 75 mg of amitriptyline for 3 days and then 150 mg daily for an active-treatment period of 6 weeks.