The pharmacokinetics of dapsone and acetylated dapsone in serum and saliva

The concentrations of dapsone (DDS) and its acetylated derivatives (MADDS and DADDS) were determined in the serum and saliva after one oral dose of dapsone until 72 hr. The peak serum concentrations of DDS and MADDS were reached, on average, at 3.8--4.3 hr after the dosage. The amounts of DADDS were negligible. The elimination half-life of the first order kinetics was, on average, at 20--21 hr for both DDS and MADDS. The study group included 6 rapid acetylators and 4 slow acetylators with the mean ratios MADDS/DDS 1.0 and 0.19, respectively. No difference in the pharmacokinetics of DDS or MADDS could be seen between the rapid and slow acetylators. The protein-free fractions of DDS and MADDS were 50 and 41 per cent, respectively, of the total serum concentrations as measured at 8 and 32 hr after the dosage. The salivary concentration of DDS was, on average, 49 per cent of the total serum concentration during the whole study period. The salivary concentration of MADDS was 40 per cent, respectively. The elimination half-life of DDS and MADDS in saliva did not differ from that in serum. Between the salivary and serum protein-free concentrations a strict correlation existed (p less than 0.001). The salivary concentration of dapsone and its monoacetyl derivative reflect the protein-free, active drug in serum.