Abstract:A simultaneous analytical method was reported for measuring the plasma levels of amitriptyline, imipramine, clomipramine, maprotiline, nor‐triptyline, desipramine, desmethylclomipramine, desmethylmaprotiline and amoxapine by high performance liquid chromatography (HPLC). The total plasma levels of each parent drug plus its desmethyl metabolite were monitored in 29 depressed patients administered with amitriptyline, maprotiline or amoxapine using the present analytical method. There were significant linear correlations between the dose per kg body weight and the total plasma levels with amitriptyline and maprotiline, but no such correlation was found with amoxapine. The ratios of total plasma levels to dose per kg body weight of these three drugs were lower in outpatients than in inpatients. These results indicate that the monitoring of plasma levels of antidepressants is useful in treating depressio