[Plasma levels of rifampicin and isoniazid and serum levels of aminotransferases in combined tuberculostatic treatment (author's transl)].

During treatment of active pulmonary tuberculosis with isoniazid, rifampicin and ethambutol in 15 patients transaminase activity increased in seven to levels of 60-340 U/l (group I). In the other eight the laboratory values remained within normal limits (group II). Rifampicin levels in group I were significantly raised at 2 and 5 hours after administration of 10 mg/kg body weight on proven fasting. There was no significant difference between the two groups for isoniazid. Estimated half-life of rifampicin was significantly longer in the first than the second group. If there is evidence of chronic liver disease (by history or by chemical tests) the rifampicin dose should be decreased to less than 10 mg/kg body weight.