The disposition of dapsone and monoacetyldapsone in the dog (38516)

Four female dogs receiving 1.0 mg dapsone (DDS)/kg iv exhibited logarithmic decline of plasma levels of DDS with a mean half-time of disappearance (T-1/2 of 11.7 hr. No evidence of acetylation of DDS to monoacetyl DDS (MADDS) was found. An equimolar dose of MADDS was deacetylated slowly to DDS by the same dogs. The mean T 1/2 of MADDS was 6.5 hr, significantly less than that of DDS. In 2-hr plasma samples after these doses of drugs, protein-binding of DDS and MADDS averaged 71 and 84%, respectively. Tests of protein-binding of the two drugs in vitro confirmed the observations in vivo.