On the pharmacokinetics of rifampicin during treatment with intermittent administration. II. Influence of age and sex and of the patients.

Pharmacokinetic investigations in 75 patients receiving their first treatment for infectious lung tuberculosis gave the following results: RMP and its products of biotransformation are excreted via the urine in smaller amounts in patients above 55 years than in younger patients. In the older age group the induction phase - as measured by the urinary excretion of RMP - is also more marked than in younger patients. Both the serum RMP-concentration and the urinary excretion of RMP are significantly higher in women than in men. The sex specific differences in pharacokinetics seem to be of clinical importance. Because of the higher serum RMP-concentration it is possible to reduce the RMP-dosage 10% in female patients, even with intermittent administration, and to diminish the risk of dose-dependent side effects.