THE METABOLISM OF CHLOROQUINE IN MAN DURING AND AFTER REPEATED ORAL DOSAGE

¹ Sterling-Winthrop Research Institute, Rensselaer, New York

The development of an analytic method which determines all of the known acidic and basic metabolites of chloroquine made possible a study of its metabolism in man during and after oral dosage at 310 mg/day for 14 days. Plasma levels and urinary excretion reached apparent plateaus at 125 µg/day, respectively, within 10 days. When medication was terminated, plasma levels and urinary excretion both decreased with a half-life of 6 to 7 days over the period of the next 4 weeks. Thereafter the urinary excretion rate decreased by 50% in 17 days, and by the 77th day off drug the mean daily output was about 1 mg. By this time a total of about 55% of the dose had been accounted for in the urine. The subjects included four Caucasians and four Negroes but no significant difference in the response of the two groups was evident. The subjects excreted only 1 to 2% of the intake of chloroquine as carboxylic acid derivatives. Otherwise, the partition of the determinable excretory products remained practically constant throughout as 70% chloroquine, 23% desethylchloroquine and smaller amounts (1-2%) of bisdesethylchloroquine and of an unidentified metabolite.

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