Toxic Alcohol Ingestion: Methanol

General concepts for all 3 toxic alcohols:

• Parent compounds (not metabolites) cause high osmolal gap
• When NAD depleted, pyruvate converts to lactate - which then causes lactic acidosis
• See metabolism of alcohols diagram below

Methanol: Factoids

Solvent found in cleaning and printing solutions, adhesives, stains, paint removers, antifreeze agent in windshield wiping fluid, camp stove fuel, gasoline additive

Pharmacology:

• Peak serum concentration 30-60 minutes, elimination half-life 12-20 hours
• Permanent blindness reported at as little as 0.1 mL/kg (6-10 mL in adults)
• Lethal dose = 1-2 mL/kg
• Metabolite (eg. formic acid) causes toxicity, but does NOT cause osmolal gap

Classic Presentation

Classic Profile

• Altered mental status
• Visual disturbances
• Abdominal pain
• High anion gap metabolic acidosis
• High osmolal gap

Signs and Symptoms

• CNS: Headache, lethargy, confusion, Parkinsonian extrapyramidal symptoms
• Ocular: Blurry vision, central scotoma, impaired pupillary response, photophobia, retinal edema (permanent damage in 25-33% of patients)
• GI: Vomiting, abdominal pain, pancreatitis

Stages of Presentation

Stage	Clinical findings
Early	Mild euphoria, inebriation, drowsiness
Latent (lasting 6-30 hours)	Normal sensorium but blurred vision
Late	Severe systemic toxicity with worsening acidosis

Management

Goal: Prevent further formation of formic acid (using fomepizole) and eliminate toxic metabolites (through dialysis)

• Folic or folinic acid supplementation to enhance formate metabolism
• Antidote: Fomipezole inhibits alcohol dehydrogenase (alternative = ethanol)

Fomipezole	Dosing
Loading dose	15 mg/kg IV
Maintenance dose	10 mg/kg IV every 12 hours x 2 days

American Academy of Clinical Toxicology guidelines

Metabolism of alcohols

References

• Jammalamadaka D, Raissi S. Ethylene glycol, methanol and isopropyl alcohol intoxication. Am J Med Sci. 2010 Mar;339(3):276-81. doi: 10.1097/MAJ.0b013e3181c94601. [PubMed]
• Kraut JA, Kurtz I. Toxic alcohol ingestions: clinical features, diagnosis, and management. Clin J Am Soc Nephrol. 2008 Jan;3(1):208-25. Epub 2007 Nov 28. [PubMed]
• Marraffa JM, Cohen V, Howland MA. Antidotes for toxicological emergencies: a practical review. Am J Health Syst Pharm. 2012 Feb 1;69(3):199-212. doi: 10.2146/ajhp110014 [PubMed]
• Barceloux DG, Bond GR, Krenzelok EP, Cooper H, Vale JA; American Academy of Clinical Toxicology Ad Hoc Committee on the Treatment Guidelines for Methanol Poisoning. American Academy of Clinical Toxicology practice guidelines on the treatment of methanol poisoning. J Toxicol Clin Toxicol. 2002;40(4):415-46. [PubMed]