Plasma hydrazine concentrations in man after isoniazid and hydralazine administration

By using a specific sensitive stable-isotope dilution gas chromatography-mass spectrometry (GC-MS) assay, hydrazine was detected in the plasma of eight healthy male volunteer subjects taking isoniazid (300 mg daily) for 2 weeks. Accumulation of hydrazine occurred in slow-acetylator phenotypes. Hydrazine was also detected in the plasma of eight out of 14 hypertensive patients treated chronically with hydralazine (200 mg daily). However, the concentrations of hydrazine observed were much lower than in the isoniazid study and were close to the limit of detection. As hydrazine is hepatotoxic, mutagenic and carcinogenic in animals, its presence in human plasma has important toxicological implications.