• 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. Nortriptylinetreated 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 <.025) and positive in the nortriptyline-treated patients (r = 0.49, P <.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<.001), Zung Score (P <.01), and percent recovered (P <.001), than those above or below the therapeutic range.
Vincent E. Ziegler, Paula J. Clayton, John T. Biggs. A Comparison Study of Amitriptyline and Nortriptyline With Plasma Levels. Arch Gen Psychiatry. 1977;34(5):607–612. doi:10.1001/archpsyc.1977.01770170117012