RT Journal Article SR Electronic T1 Studies on the effects of isoniazid on acetylhydrazine metabolism in vivo and in vitro. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 237 OP 240 VO 7 IS 4 A1 J A Timbrell A1 J M Wright YR 1979 UL http://dmd.aspetjournals.org/content/7/4/237.abstract AB The interaction of isoniazid with its hepatotoxic metabolite acetylhydrazine has been studied. In vitro, isoniazid at a concentration of 0.5 mM was found to inhibit the microsomal metabolism of acetylhydrazine to a reactive acylating species. In vivo, however, coadministered isoniazid inhibited the acetylation to diacetylhydrazine and concomitantly increased the microsomal metabolism of 14C-acetylhydrazine to a reactive intermediate which covalently bound to liver macromolecules. Comparison of urinary metabolites of isoniazid at two dose levels indicated that acetylation of acetylhydrazine produced as a metabolite may be inhibited by the parent drug.