A simple method for determining acetylator phenotype using isoniazid.

A comparison was made between the results of acetylator phenotyping by isoniazid (INH) half-life measurements based on samples taken for 6 h after a single oral dose (200 mg), and by determination of the ratio of acetylisoniazid (Ac.INH) to isoniazid in the 3 h samples. In the 32 subjects, examined, there was complete agreement about classification of the subject as a fast (t1/2 less than 130 min; Ac.INH/INH greater than 1.5) or slow acetylator (t1/2 greater than 130 min; Ac.INH/INH less than 1.5). The single sample test appears to be as reliable as the more time-consuming isoniazid half-life method.