Urinary excretion of mefloquine and some of its metabolites in African volunteers at steady state.

Because of the extremely long terminal elimination half-life of mefloquine it is practically impossible to measure quantitatively its urinary excretion after a single dose. Indeed, a correct estimation would require collection of urine over a period of several months. This difficulty was overcome by measuring excretion in the course of a multiple-dose study when steady-state conditions had been reached. Six male African volunteers were given at an interval of 1 week 250 mg mefloquine base in the form of its hydrochloride. Urine was quantitatively collected from each subject during the 11th week and analyzed for unchanged drug and its alcohol and acid metabolites. Excretion of the unchanged drug and of its acid metabolite amounted respectively to 9% (5.2-13.1%) and 4.2% (2.9-6.2%) of the weekly dose. Concentrations of the alcohol metabolite were too low to be measured.