Evidence for a trimodal pattern of acetylation of isoniazid in uremic subjects.

Isoniazid metabolic clearance values were calculated retrospectively and plotted on a frequency distribution histogram. A trimodal distribution pattern was observed. According to a two-allele codominant model, the mean clearance values of the slow and rapid acetylators closely predicted the mean clearance value for the intermediate acetylators. The potential clinical implications of identifying intermediate and rapid acetylators of isoniazid and its use in renal failure are discussed.