title: Extremely slow formate elimination in severe methanol poisoning: a fatal case report.
abstract: Methanol poisoning is a potentially fatal medical emergency because of its metabolism to formic acid. The half-life of formate has been reported in the range of 2.5-12.5 hours, but the degree of inter-individual variation is not known. We studied methanol and formate kinetics in a case of late diagnosed methanol poisoning with persisting metabolic acidosis and circulatory failure.
  
  
  METHODS
  A 63-year-old man was referred to our hospital with a tentative diagnosis of stroke. He was awake on admission, but he soon deteriorated in the emergency department and a metabolic acidosis was revealed. Methanol poisoning was then suspected approximately five hours after admission but in spite of intensive treatment he died after six days.
  
  
  RESULTS
  The S-methanol half-lives during treatment with fomepizole before and during hemodialysis were 49.5 and 4.1 hours, respectively, while the similar half-lives of S-formate were 77.0 and 2.9 hours. S-fomepizole was measured and found to be within the therapeutic range during treatment.
  
  
  CONCLUSIONS
  The patient was treated with the established dosing regimen for fomepizole and the measured S-fomepizole levels throughout the treatment were adequate; the S-methanol elimination also suggests that methanol metabolism was blocked. Hence, other explanations for this exceptionally long formate half-life include slow formate metabolism, due to small hepatic folate stores or to genetic deficiencies in formate-metabolizing enzymes, or slow formate excretion, due to renal tubular acidosis, to a non-oliguric renal failure, or to genetic deficiencies in the renal formate transporters.
  
  
  CONCLUSIONS
  This case report indicates that the half-life of S-formate may have greater inter-individual variation than earlier expected, being by far the longest half-life reported in the medical literature. These results support the use of hemodialysis in the treatment of such patients.
authors.affiliation: Department of Acute Medicine, Ullevaal University Hospital, Oslo, Norway. kehovda@yahoo.com
authors.forename: Knut Erik
authors.initials: KE
authors.lastname: Hovda
authors.forename: Haavard
authors.initials: H
authors.lastname: Mundal
authors.forename: Petter
authors.initials: P
authors.lastname: Urdal
authors.forename: Kenneth
authors.initials: K
authors.lastname: McMartin
authors.forename: Dag
authors.initials: D
authors.lastname: Jacobsen
mesh_terms: D000931:Antidotes / Q000627:therapeutic use; D017809:Fatal Outcome; D000077604:Fomepizole; D005561:Formates / Q000097:blood* / Q000652:urine; D006207:Half-Life; D006801:Humans; D008297:Male; D000432:Methanol / Q000097:blood / Q000506:poisoning* / Q000652:urine; D008875:Middle Aged; D011720:Pyrazoles / Q000627:therapeutic use; D006435:Renal Dialysis
chemical_list: D000931:Antidotes; D005561:Formates; D011720:Pyrazoles; C030544:formic acid; D000077604:Fomepizole; D000432:Methanol