Isoniazid Isoflurane

Isoniazid may increase the metabolism of enflurane, isoflurane or sevoflurane and thereby increase plasma-fluoride concentrations. However, this does not seem to have resulted in clinically important renal impairment. 

A 46-year-old woman underwent anaesthesia for renal transplantation 6 days after starting isoniazid 300 mg daily. Anaesthesia was indueed with intravenous thiopental and maintained for 4 hours with 60% nitrous oxide, fentanyl and isoflurane. Serum fluoride ions inereased from 4.3 mieromol preoperatively to approximately 30 mieromol between 2 and 8 hours after starting isoflurane. However, no impairment of renal funetion occurred. A second patient who was given 5 times the first patient s exposure to isoflurane and who had received isoniazid for 13 years showed no increase in serum fluoride concentrations over preoperative values, but did show an increase in trifluoroacetic acid levels. ... 

Gauntlett IS, Koblin DD, Fahey M Konopka K, Gruenke LD, Wa ell L, Eger El. Metabolism of isoflurane in patients receiving isoniazid. AnesthAnalg (1989) 69,245-9. 

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