Disposition of dapsone and monoacetyldapsone in rats.

Female Buffalo and Lewis rats receiving 1.0 mg DDS/kg ip exhibited higher plasma levels of DDS and its monoacetylated metabolite, MADDS, than did male rats of each strain receiving the same dose. The fraction of the total measured drug in plasma as MADDS at 8 hr in female rats of both strains ranged from 43 to 62% compared with a range of 28-31% in male rats. Plasma half times of disappearance (T1/2) of DDS ranged from 5.0 to 6.8 hr and were not different among sexes and strains. Deacetylation of MADDS to DDS occurred when equimolar doses of MADDS were administered. An approach to a steady state of acetylation-deacetylation was indicated by comparing the percentage MADDS of the total drug in plasma in the respective sexes and strains receiving both drugs. T1/2 values of MADDS were significantly lower than values for DDS in Lewis rats. They were not different in Buffalo rats. Protein binding studies in plasma from rats receiving 5.0 mg DDS or 5.8 mg MADDS/kg showed 67-72% binding of DDS and 91% binding of MADDS. These in vivo observations were confirmed by in vitro binding studies. Comparison of these results with those of earlier studies in mice and man indicates that the rat is a better model of man than is the mouse for studies on the disposition of DDS.