Application of an individually predicted dosage of amitriptyline to the treatment of depression.

The treatment of depressed patients with a fixed dose of amitriptyline is compared to treatment with an individualized dose calculated by means of a simple pharmacokinetic test. Clinical response and the development of side-effects are compared between the two groups of patients. Although the numbers in the groups were small, the clinical results lend little support to the concept of a therapeutic range of plasma drug concentrations for amitriptyline, and none of the plasma concentrations was high enough to produce serious toxic effects. No obvious clinical advantage was observed in the predicted dose treatment group as assessed by a reduction in depression ratings. The dose prediction test did however more than halve the variance in blood drug concentrations, and its usefulness in preventing high and potentially toxic concentrations is indisputable.