Plasma concentrations of the enantiomers of halofantrine and its main metabolite in malaria patients.

The plasma concentrations of the enantiomers of halofantrine and its N-desbutyl metabolite in six patients with malaria were measured after oral administration of 3 x 750 mg doses of micronised, racemic halofantrine hydrochloride given at 6-hour intervals. Significant differences were observed between the plasma concentrations of the enantiomers both of halofantrine and its N-monodesbutyl metabolite. AUC(0)84h values were higher for (+)halofantrine (9917 micrograms.ml-1.h) than for (-)-halofantrine (6127 micrograms.ml-1.h). The clinical significance of these observations is not known. The isomers have equipotent activity in vitro but their relative toxicity has not yet been assessed.