ACETYLATION OF DAPSONE BY HUMAN WHOLE-BLOOD

We studied the acetylation of dapsone (DDS) in vitro by whole blood taken from subjects with known acetylator phenotype. The acetylation of DDS by whole blood was both incubation time- and DDS concentration-dependent. Thus, it is highly recommended to separate plasma immediately after blood withdrawal during acetylation phenotyping using DDS. para-aminobenzoic acid (PABA) substantially inhibited the acetylation of DDS by whole blood taken from both slow and rapid acetylators, while procainamide (PAD) significantly inhibited DDS acetylation by whole blood taken from slow acetylators. At the highest PAD concentration used (208 muM), DDS acetylation by whole blood taken from rapid acetylators was also inhibited. In contrast, sulphanilamide (SAD) failed to produce any significant inhibition of the acetylation of DDS by whole blood taken from either slow or rapid acetylators. Furthermore, there was no correlation between DDS acetylation by whole blood in vitro and the acetylator status of the subject. It is therefore not possible to predict the acetylator phenotype by studying DDS acetylation by human whole blood. These results indicate that the DDS N-acetyltransferase of human whole blood is most probably of the monomorphic type.