Isoniazid phenotyping of black as well as white patients.

The isoniazid phenotyping in black patients from Birmingham (Alabama) as well as from South Africa yielded a higher frequency of fast inactivation than that in the Canadian and U.S. white participants. Following an oral test dose of 10 mg isoniazid per kilogram, the incidence of fast acetylation was 58.7 and 60.3% in South African and Birmingham blacks, respectively. In the Canadian and Birmingham Caucasians the rate was 41.9 and 41.0%, respectively.