Methanol toxicity

Methanol toxicity

Lewis structure of methanol

Methanol toxicity is a form of poisoning that occurs when methanol, a type of alcohol, is ingested, inhaled, or absorbed through the skin. Methanol is a colorless, volatile liquid with a distinctive odor, commonly used as an industrial solvent, antifreeze, and fuel. It is also found in small amounts in various consumer products.

Pathophysiology

Methanol itself is not highly toxic, but it is metabolized in the liver to formaldehyde and then to formic acid, which are highly toxic metabolites. The enzyme alcohol dehydrogenase converts methanol to formaldehyde, and aldehyde dehydrogenase further converts formaldehyde to formic acid. Formic acid accumulation leads to metabolic acidosis and can cause damage to the optic nerve, resulting in blindness.

Symptoms

The symptoms of methanol toxicity can vary depending on the dose and duration of exposure. Initial symptoms may include:

• Headache
• Dizziness
• Nausea
• Vomiting
• Abdominal pain

As the condition progresses, more severe symptoms can develop, such as:

• Visual disturbances (e.g., blurred vision, "snowfield" vision)
• Blindness
• Seizures
• Coma
• Respiratory failure

Diagnosis

Diagnosis of methanol toxicity is based on clinical presentation and laboratory tests. Key diagnostic indicators include:

• Elevated anion gap metabolic acidosis
• Increased serum methanol concentration
• Presence of formic acid in the blood

Treatment

The primary goals of treatment are to inhibit methanol metabolism, correct metabolic acidosis, and remove methanol and its toxic metabolites from the body. Treatment options include:

• Fomepizole: An inhibitor of alcohol dehydrogenase, preventing the conversion of methanol to formaldehyde.
• Ethanol: Competes with methanol for alcohol dehydrogenase, reducing the formation of toxic metabolites.
• Sodium bicarbonate: Used to correct metabolic acidosis.
• Hemodialysis: Effective in removing methanol and formic acid from the blood.

Prevention

Preventing methanol toxicity involves minimizing exposure to methanol-containing products and ensuring proper labeling and storage. Public education on the dangers of methanol ingestion and the importance of seeking immediate medical attention if exposure occurs is crucial.

Related pages

• Alcohol poisoning
• Formaldehyde
• Metabolic acidosis
• Optic nerve