The Pharmacokinetics of Bifemelane Hydrochloride in Elderly Patients (2nd Report)

The urinary excretion of metabolites of bifemelane hydrochloride (BFM) was studied in both young and elderly volunteers. BFM (50mg) was administered orally after breakfast to young healthy subjects (n=8) and elderly subjects (n=15). Urine was collected separately 0-8 and 8-24hr after administration, and the concentrations of metabolites including a new identified metabolite, M-2 sulfate, were determined. The excretion rate of M-2 sulfate within 24hr after administration, which was 27.55±3.25% of the dose in young and 20.88±1.56% of the dose in elderly subjects, was larger then that of any other metabolites. The excretion rate of total metabolites in the young for 8hr post-administration was 54.11±2.94% of the dose, which was significantly higher (P<0.01) than that in the elderly, 27.53±2.39%. On the other hand, the 8-24hr excretion rate of total metabolites in the elderly, 26.16±2.63% of the dose, was higher than in the young, 17.93±2.25% of the dose. The urinary excretion ratio of BFM metabolites in the elderly was less than that in the young, but the difference was not significant. The delay of urinary excretion of BFM metabolites in the elderly is considered to be mainly due to both the lower hepatic metabolic rate of BFM and renal excretion rate of its metabolites.