Plasma concentrations of sulfadoxine-pyrimethamine and of mefloquine during regular long term malaria prophylaxis.

The plasma concentrations of sulfadoxine, pyrimethamine, mefloquine and its major metabolite were determined in 18 healthy male volunteers who had regularly taken either 500 mg of sulfadoxine and 25 mg of pyrimethamine (Fansidar) weekly or 250 mg mefloquine regularly every 14 d during 6 months for malaria prophylaxis. The mean trough concentrations of sulfadoxine, pyrimethamine and mefloquine were 194, 0.28 and 1.48 mumol/litre and the mean half lives were 7.7, 4.2 and 25 d respectively. The variation in area under the curve for the 3 drugs was only 2-3 fold. The findings do not indicate that drug accumulation or induction of metabolism occurred during long-term usage.