No circadian effect on nortriptyline kinetics in man.

Kinetics of a single 100-mg dose of nortriptyline were studied in 10 normal men who took this dose at 9 A.M. in the morning and on another occasion at 9 P.M. Only minimal differences in kinetic parameters were observed, none enough to be of any clinical consequence. A rather high first-pass metabolism of the drug was evident by high plasma concentrations of 10-hydroxynortriptyline. It is thus unlikely that the recent custom of giving single daily doses of tricyclic antidepressants in the evening excludes regimens with more favorable drug kinetics.