• The therapeutic efficacy, plasma levels, and psychomotor effects of tryptophan (L-tryptophan), clomipramine hydrochloride, and doxepin were investigated in "neurotically" depressed outpatients. The tricyclic antidepressants were significantly more efficacious than tryptophan in inducing remission. The alleviation of depression was preceded by an improvement of the initially slow information-processing rates in the depressed patients. The plasma levels of the tricyclics that were associated with a therapeutic response were significantly lower than those reported in "endogenously" depressed inpatients.
Linnoila M, Seppala T, Mattila MJ, Vihko R, Pakarinen A, Skinner JT. Clomipramine and Doxepin in Depressive NeurosisPlasma Levels and Therapeutic Response. Arch Gen Psychiatry. 1980;37(11):1295-1299. doi:10.1001/archpsyc.1980.01780240093011