Fomepizole may change indication for hemodialysis in methanol poisoning: prospective study in seven cases

Abstract

Background: Treatment of methanol poisoning includes administration of buffer, antidote and hemodialysis. The role of hemodialysis using the new antidote fomepizole has not been studied. We studied the kinetics of methanol and formate during hemodialysis, and the possibility for delayed hemodialysis in the methanol poisoned patients without severe metabolic acidosis or visual disturbances.

Patients and methods: Prospective case series study on methanol, formate and dialysis kinetics in 7 cases of severe methanol poisoning treated with buffer, fomepizole and hemodialysis (average 7 hours, range 5 - 8). Four patients were dialyzed early after diagnosis was obtained, while three were dialyzed "electively" the next day.

Results: The median pH upon admission was 6.9 (range 6.6 - 7.5) and median base deficit 20.4 mmol/l (range 5.1 - 30.0). Their median S-methanol was 76.3 mmol/l (range 15.6 - 140.6) and S-formate 13.6 mmol/l (range 3.3 - 21). The median half-life of methanol during fomepizole treatment before dialysis was 71.2 hours (range 69.3 - 77); compared to 2.5 hours (range 1.7 - 3.3) during procedure. The median half-life of formate during dialysis was 1.7 hours (range 1.5 - 1.9). The median dialysis clearance of methanol was 222 ml/min (range 204 - 232) and for formate 225 ml/min (range 220 - 229) at a blood flow of 250 ml/min. One patient died and 2 were discharged with permanent visual and cerebral sequelae, whereas one died one year later. All three patients, in whom "elective" hemodialysis was performed, were discharged without sequelae.

Conclusion: The efficacy and side effect profile of fomepizole may change the role of hemodialysis in methanol poisoning. More patients may be stabilized in local hospitals and transferred for "elective" dialysis, if methanol removal is still indicated after correction of metabolic acidosis.