Urinary excretion of nortriptyline and five of its metabolites in man after single and multiple oral doses.

The urinary excretion of nortriptyline (NT) and five of its metabolites was studied by quantitative gas chromatography in 22 twins and 7 unrelated healthy subjects after single (1 mg/kg) and multiple oral doses (0.4 mg/kg t.i.d.) of NT hydrochloride. A mean recovery of 62% of the dose was found after both single and multiple doses. The metabolite pattern in the urine was qualitatively and quantitatively identical in the two regimes, but there were marked variations in the pattern of metabolites between individuals. The disappearance rate of NT from the plasma was mainly determined by the metabolism of NT to 10-hydroxynortriptyline, which varied considerably between individuals. The data suggest that in certain rapid NT metabolizers, the upper limit for the overall clearance of NT from the plasma (if extrahepatic metabolism is assumed to be negligible) might be set by the blood flow through the liver. [ABSTRACT FROM AUTHOR]