A comparison study of amitriptyline and nortriptyline with plasma levels.

Forty-one depressed outpatients were treated for six weeks after random assignment to amitriptyline hydrochloride (N = 22) or nortriptyline hydrochloride (N = 19). On a mean daily dose of 119 mg, amitriptyline-treated patients had a mean tricyclic level (amitriptyline plus nortriptyline) of 120 ng/ml. Nortriptyline-treated patients on a mean dose of 117 mg/day had a mean nortriptyline level of 141 ng/ml. The two drugs were equally effective in the treatment of depression. The correlation between the Hamilton Score and the mean tricyclic level was negative in the amitriptyline-treated patients (r = -0.54, P less than .025) and positive in the nortriptyline-treated patients (r = -0.49, P less than .05). Patients treated with amitriptyline or nortriptyline with plasma levels within the therapeutic range, defined in other laboratories, had a better response, as measured by the Hamilton Score (P less than .001), Zung Score (P less than .01), and percent recovered (P less than .001), than those above or below the therapeutic range.