A simple pharmacokinetic method for separating the three acetylation phenotypes: a preliminary report.

1 Until recently, phenotyping the N-acetyltransferase enzyme had been restricted to distinguishing the slow acetylators from the rapid. Further separation of the heterozygous rapid phenotype from the homozygous rapid phenotype has only been possible by detailed pharmacokinetic studies using sulphadimidine and necessitating prolonged plasma sampling. 2 A simple method of deriving the basic pharmacokinetic parameters is presented. In this study of ten healthy volunteers, one urine sample and hourly plasma sampling over only 5 h enabled calculation of the total body (TBC) and metabolic clearances (MC) wih enough accuracy to distinguish the three (slow, intermediate and rapid) acetylator phenotypes. The spread of the distribution for the elimination rate constant was however too wide to enable their clear separation.