Distribution of acetylator phenotype in relation to age and sex in Swedish patients. A retrospective study.

In 310 Swedish patients, the distribution of acetylator phenotype was studied by determination of the half-life of isoniazid (INH T1/2). The expected bimodal distribution was found in the complete study group, but was not always clearly apparent after subgrouping for age and sex. Mean INH T1/2 was higher in males and tended to increase with age. The difference in INH T1/2 between males and females was small in younger individuals (below 46 years of age) and showed a gradual increase with age. In older individuals (above 65 y) mean INH T1/2 was 42 min longer in males than in females. In the females, mean INH T1/2 was relatively constant in all age groups. The effect of age on acetylator phenotype, previously reported by other workers, appears to have been confirmed but only in males. It may be influenced by concurrent treatment for certain diseases.