Methanol

Revised 10/09

Methanol also referred to as methyl alcohol or wood alcohol is widely used in commercial and industrial settings and can also be found in the home. Methanol is found as a component of many paint removers, varnishes, shellacs, windshield washing fluid and antifreeze. Methanol is derived as a by-product of wood distillation. Poisoning occurs with consumption of contaminated whiskey, accidental ingestion’s, and suicide attempts. Toxicity of methanol is due to the formation of toxic metabolites; formaldehyde and formic acid.

Metabolism:

                              Methanol → Formaldehyde → Formic acid → Folate

Pathophysiology:

 Methanol is a colorless, volatile liquid with distinct odor. Methanol is absorbed well in the GI tract. Methanol is primarily eliminated by liver through metabolism but a small percentage (2-5%) is renal excreted. Toxicity comes from the formation of formaldehyde and formic acid through hepatic dehydrogenases. The onsets of symptoms are associated with the accumulation of formic acid.  Formate inhibits mitochondrial respiration leading to tissue hypoxia and lactate formation. Formate production occurs in the retina and may lead to optic papillitis and retinal edema.

Clinical Features:

Initial symptoms may develop anywhere from 40 minutes to 72 hours after ingestion. The usual latent period is 12 to 18 hours. Coingestion with alcohol may delay symptoms. These signs and symptoms include:

• Headache, vertigo, lethargy, confusion, coma, and seizures. Initial symptoms may resemble ethanol intoxication.
• Hyperemia of optic disc and reduced papillary response to light,  “Looking into a snow field”, blurred vision, decreased visual acuity, diplopia, and photophobia.
• Nausea, vomiting, abdominal pain.
• Severe anion gap acidosis, co-ingestion of alcohol my delay onset of symptoms.

Treatment:

Support vital functions. GI decontamination with charcoal is not effective unless other co-ingestants are involved. Monitor arterial blood gases and electrolytes. Use sodium bicarbonate to correct the acidosis.  Calculate an anion gap and osmolar gap. Obtain a blood methanol level.

 Fomepizole has been FDA approved as the specific antidote for the treatment of methanol toxicity. It works by inhibiting the enzyme alcohol dehydrogenase which is responsible for the conversion of methanol to its toxic metabolites formaldehyde and formic acid. Ethanol therapy may be used in the absence of fomepizole therapy.
Adjunct therapy with folate and folinic acid can be initialized. Hemodialysis is effective at removing methanol and its metabolites from the blood.

Disposition:

Patients with serious signs and symptoms associated with methanol intoxication or a history of significant ingestion even in the absence of symptoms should be admitted to an intensive care setting.

References:

Antizol Product Monograph. Orphan Medical, Inc. Minnetonka, MN 1997.

Brent J, McMartin K, Philips S, Aaron C, Kulig K: Fomepizole for the Treatment of Methanol Poisoning. N Engl J of Med 344; 424-429, 2001.

Barceloux DG, Bond R, Krenzelok EP, Cooper H, Vale JA: American Academy of Clinical Toxicology Practice Guidelines on the Treatment of Methanol Poisoning. Clin Tox 40(4), 415-446 (2002).

Jacobsen D, McMartin KE: Antidotes for Methanol and Ethylene Glycol Poisoning. Clin Tox 35(2), 127-143 (1997)

Hanston P, Lambermont JY, Mahieu P: Methanol Poisoning During Late Pregnancy. Clin Tox 35(2); 187-191 (1997)

Roy M, Bailey B, Chalut D, Senecal PE, Gaudreault P: What are the Adverse Effects of Ethanol used as an Antidote in the Treatment of Suspected Methanol Poisoning in Children? Clin Tox 41(2); 155-161 (2003)

Kostic MA, Dart RC: Rethinking the Toxic Methanol Level. Clin Tox 41(6); 793-800, 2003

Sivilotti MLA, Ford MD Irwin and Rippe’s Intensive Care Medicine 5^th ed. 2003 Chapter 123 Alcohols and Glycols.

Anderson, Ilene. Methanol: Poisoning and Drug Overdose 4^th ed. McGraw-Hill 2004. 260-261.
 
If you have any questions regarding exposure to and/or treatment for Methanol, please call the poison center at 1-800-222-1222 …24 hours a day, 7 days a week.