Dose‐dependent changes in sulfamethazine kinetics in rapid and slow isoniazid acetylators

Abstract

The pharmacokinetics of sulfamethazine (SMZ) was studied in 44 healthy volunteers. After an oral dose of 10 mg/kg we found the usual distribution of rapid and slow acetylators. The differences in the t^½s between the phenotypes were not due to variations in renal clearance. Repeat studies at this dose showed very little intraindividual variation in t^½s. After a 40 mg/kg dose there was an increase in the t^½ of SMZ in every subject. The implications of these results on methods of phenotyping are discussed.