[Modification during treatment of the rate of acetylation of isoniazide clinically or biologically detectable hepatic damage (author's transl)].

The rate of acetylation of isoniazid is usually constant in a given subject. The authors report here a case where despite an adjusted initial dose there was a decrease in the rate of acetylation during treatment with INH-rifampicin and ethambutol, without hepatic involvement but accompanied by retrobulbar optic neuritis. The role of ethambutol and/or an overdose of isoniazid are discussed. The technique for its estimation is also described.