Methyl Alcohol

(BAN, USAN, rINN)
Methyl Alcohol Chemical formula
Synonyms: Metanol; Metanoli; Metanolis; Méthanol; Methanol; Methanolum.
Cyrillic synonym: Метиловый Спирт.

💊 Chemical information

Chemical formula: CH3OH = 32.04.
CAS — 67-56-1.

Pharmacopoeias.

In Eur.. Also in USNF.

Ph. Eur. 6.2

(Methanol). A colourless, clear, volatile, hygroscopic liquid. It is flammable. B.p. about 64°. Relative density 0.791 to 0.793. Miscible with water and with dichloromethane. Store in airtight containers. The BP 2008 gives Methyl Alcohol as an approved synonym.

USNF 26

(Methyl Alcohol). A clear, colourless, flammable liquid having a characteristic odour. Miscible with water, with alcohol, with ether, with benzene, and with most other organic solvents. Store in airtight containers remote from heat, sparks, and open flames.

💊 Adverse Effects

Immediate signs of acute poisoning after ingestion of methyl alcohol resemble those of ethanol (alcohol; ethyl alcohol) intoxication, but are milder. Characteristic symptoms of methyl alcohol poisoning are caused by toxic metabolites and develop after a latent period of about 12 to 24 hours, or longer if taken with ethanol. The outstanding features of poisoning are metabolic acidosis with rapid, shallow breathing, visual disturbances which often proceed to irreversible blindness, and severe abdominal pain. Other symptoms include headache, gastrointestinal disturbances, pain in the back and extremities, and coma which in severe cases may result in death due to respiratory failure or, rarely, to circulatory collapse. Mania and convulsions occasionally occur. Individual response to methyl alcohol varies widely. Ingestion of 30 mL is considered to be potentially fatal. Absorption of methyl alcohol through the skin or inhalation of the vapour may also lead to toxic systemic effects.
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9. Hantson PE. Intoxication aiguë par le méthanol : physiopathologie, pronostic et traitement. Bull Mem Acad R Med Belg 2006; 161: 425–34.

Handling.

Suitable precautions should be taken to avoid skin contact with methyl alcohol as it can penetrate skin and produce systemic toxicity.

💊 Treatment of Adverse Effects

Gastric aspiration may be considered if the patient presents within 1 hour of ingesting methyl alcohol. Activated charcoal is probably of little use as it does not absorb significant amounts of methyl alcohol. Metabolic acidosis should be corrected immediately with intravenous sodium bicarbonate. If significant amounts of methyl alcohol have been ingested, early treatment with an antidote (ethanol or fomepizole) is recommended. Ethanol delays the oxidation of methyl alcohol to its toxic metabolites formaldehyde and formic acid; dosage is adjusted to achieve and maintain a blood-ethanol concentration of 1 to 1.5 mg/mL. An oral dose for a 70-kg adult of about 150 mL of an ethanolic solution containing 40% v/v of C2H5OH has been suggested. Alcoholic spirits (such as whisky, gin, or vodka) may often be of the suitable strength. If required, an ethanolic infusion containing 10% v/v of C2H5OH may then be given as maintenance for which the following doses have been used:
for an average adult, 1.38 mL/kg per hour
for a non-drinker or child, 0.83 mL/kg per hour
for a chronic drinker, 1.96 mL/kg per hour
The infusion should be continued until methyl alcohol concentrations are undetectable, or fall below 50 micrograms/mL with resolution of systemic toxicity. Fomepizole, an inhibitor of alcohol dehydrogenase, is also used; it inhibits the metabolism of methyl alcohol to its toxic metabolites. Haemodialysis may be indicated to increase the removal of methyl alcohol and its toxic metabolites. Peritoneal dialysis has been used but is less efficient. Haemodialysis may be considered if the blood-methyl alcohol concentration is greater than 500 micrograms/mL, if there is severe metabolic acidosis unresponsive to sodium bicarbonate, or there is visual disturbance, CNS toxicity, renal failure, or severe electrolyte disturbance. If haemodialysis is used, a constant blood-ethanol concentration may be ensured either by increasing the ethanol infusion rate or by addition of ethanol to the dialysate fluid. Treatment should not be stopped prematurely since oxidation and excretion of methyl alcohol may continue for several days; patients should, therefore, be closely observed and monitored. Suitable supportive treatment should be carried out as required. Folinic acid and folic acid have been given in the treatment of methyl alcohol toxicity because they may enhance the metabolism of formic acid.
1. Barceloux DG, et al. 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: 415–46.

💊 Pharmacokinetics

Methyl alcohol is readily absorbed from the gastrointestinal tract and distributed throughout the body fluids. It may also be absorbed after inhalation or through large areas of skin. Oxidation by alcohol dehydrogenase with formation of formaldehyde and formic acid takes place mainly in the liver and also in the kidneys. These metabolites are thought to be largely responsible for the characteristic symptoms of methyl alcohol poisoning. Metabolism is much slower than for ethanol, which competitively inhibits the metabolism of methyl alcohol. Oxidation and excretion may continue for several days after ingestion. Elimination of unchanged methyl alcohol via the lungs and in the urine is a minor route of excretion.

💊 Uses

Methyl alcohol is used as a pharmaceutical and industrial solvent. It is also used as ‘wood naphtha’ to denature ethanol in the preparation of industrial methylated spirits. Methyl alcohol is also used as an extraction solvent in food processing.
Published November 17, 2018.