[The different inactivation of isoniazid in intermittent chemotherapy (author's transl)].

A ratio-test (Isoniazid: acetyl-isoniazid) is used for phenotyping the Isoniazid-inactivation. The border-line between both the phenotypes is determinated. The influence of age and weight of the patients is studied. Usefully results are obtained after application per os of an uniform dosage and a sampling period for urine of 4 hours. Increasing the dosage to 900 mg the portion of isoniazid arises mmore than proportionally, more distinct in rapid than in slow inactivators. Therefore the differences between the two phentoypes are diminished. The clinical importance of these results is discussed.