Plasma levels, psychophysiological variables, and clinical response to amitriptyline

Hamilton depression scale ratings and physiological measurements were made for 37 patients with primary depression before treatment with amitriptyline (150 mg/day) and again after 2 and 4 weeks of treatment; plasma drug levels were determined weekly. Improvement was maximal at mean amitriptyline + nortriptyline concentrations of 125-200 ng/ml (14 patients), while at lower levels the outcome was significantly poorer (12 patients). Highly variable results were seen in 11 patients with levels between 200 and 301 ng/ml, with lesser improvement occurring in those patients who exhibited poor habituation of the skin resistance response before treatment. Other psychophysiological variables showed significant changes during treatment, but no correlation with clinical results or drug levels.