title: Methanol and formate kinetics during treatment with fomepizole.
abstract: OBJECTIVE
  Methanol is metabolized by alcohol dehydrogenase to formaldehyde, and further to formic acid, which is responsible for the toxicity in methanol poisoning. Fomepizole (4-methylpyrazole) is a potent competitive inhibitor of alcohol dehydrogenase and is used as an antidote to treat methanol poisonings. We report serum methanol kinetics in eight patients treated with bicarbonate and fomepizole only.
  
  
  METHODS
  Prospective case series study of eight patients with methanol poisoning, who were selected to fomepizole and bicarbonate treatment only, because of moderate metabolic acidosis. Three of the patients were later dialyzed, because of high serum methanol concentrations and very slow methanol elimination.
  
  
  RESULTS
  Upon admission the median pH was 7.27 (range 7.12-7.50), median base deficit was 15 mmol/L (5-22 mmol/L) and median serum methanol was 20.4 mmol/L (65 mg/dL) (range 8.4-140.6 mmol/L). The kinetics of methanol during fomepizole treatment in six patients was best described by a first-order elimination one-compartment model. The mean correlation coefficient (R2) describing the first-order elimination model in all eight patients was 0.95 (range 0.90-0.99). The mean plasma half-life (t(1/2)) of methanol during fomepizole treatment was 52 h (range 22-87); the higher the serum methanol, the longer the T(1/2). Mean half-life of serum formate was 2.6 h, when methanol metabolism was assumed blocked by fomepizole and no folinic acid was given. This rapid formate elimination in nonacidotic patients may be explained by high renal excretion of formate.
  
  
  CONCLUSIONS
  Based on our data, methanol-poisoned patients with moderate metabolic acidosis and methanol levels up to 19 mmol/L (60 mg/L) may safely be treated with bicarbonate and fomepizole only, without dialysis.
authors: Department of Acute Medicine, Medical Division, Ullevaal University Hospital, Oslo N-0407, Norway. kehovda@yahoo.com
authors: Knut Erik
authors: KE
authors: Hovda
authors: Kirsti Svendsen
authors: KS
authors: Andersson
authors: Petter
authors: P
authors: Urdal
authors: Dag
authors: D
authors: Jacobsen
mesh_terms: D000138:Acidosis / Q000209:etiology / Q000628:therapy; D000328:Adult; D000368:Aged; D000931:Antidotes / Q000627:therapeutic use*; D001639:Bicarbonates / Q000627:therapeutic use; D002849:Chromatography, Gas; D003956:Dialysis; D000077604:Fomepizole; D005561:Formates / Q000097:blood / Q000493:pharmacokinetics*; D006207:Half-Life; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008297:Male; D000432:Methanol / Q000097:blood / Q000493:pharmacokinetics* / Q000506:poisoning*; D008875:Middle Aged; D011446:Prospective Studies; D011720:Pyrazoles / Q000627:therapeutic use*
chemical_list: D000931:Antidotes; D001639:Bicarbonates; D005561:Formates; D011720:Pyrazoles; D000077604:Fomepizole; D000432:Methanol