Methanol Poisoning

Poisoning with methanol (methyl alcohol) is a very dangerous condition that can lead to serious health problems or even death.


The poisoning is caused by ingestion of a substance called methanol. Methanol is used n industry and it is also produced in the process of poor-quality distillation of alcohol, which can occur in uncontrolled home distilleries. For example in Russia and other countries of the Eastern Europe, where many people burn hard liquor at home, the final product of their efforts often contains a significant dose of methanol.


Alcohol is a chemical substance known as ethanol. It is largely similar to methanol including the taste, color and aroma. However, ethanol in low doses causes only slight intoxication, while similar doses of methanol are gravely dangerous. The answer is a different chemical pathway of both substances in the body.


Ethanol is converted by an enzyme (alcohol dehydrogenase) to a substance known as acetalaldehyde (which is responsible for the hangover) and by another enzyme it is converted to a harmless acetic acid, which can be further metabolically processed.


Methanol is converted with the same enzyme as ethanol, i.e. by the alcohol dehydrogenase. The reaction product, however, is different – it is an aggressive substance formaldehyde, which is later converted into a relatively strong organic formic acid (the same substance is present in ant venom). These products of methanol metabolism are highly toxic and may cause fatal poisoning.


The poisoning by methanol has usually two main mechanisms. A person can drink methanol accidentally or on purpose in suicide attempt.


Due to the fact that methanol itself is not toxic until its metabolic conversion, the symptoms occur gradually. The affected person suffers from headache, nausea, vomiting, confusion, coma and death. A lethal dose of formic acid is present in about 100 milliliters of pure methanol. The products of methanol are especially toxic to the optic nerve and a dose of only 10 milliliters of pure methanol can cause its permanent damage and blindness.


In industry, all bottles containing methanol should be properly labeled. In some countries, the industrial methanol is stained by blue dye to prevent its confusion with alcohol. It is highly inadvisable to drink alcohol from unknown sources such as unsafe home distilleries. 


The basic therapy of methanol poisoning is the administration of ethanol. As first aid, any hard liquor may be use and it is also possible to intravenously administer some alcohol-containing solutions. We use the fact that ethanol and methanol are converted by the same enzyme. The enzyme preferably processes ethanol molecules and the methanol molecules must wait, which gives the body time to excrete methanol, before it is converted to the toxic products. The target alcohol blood level in the patient is about 1 per mille to reach the desired protective effect. If necessary, the doctors can use a dialysis machine, which is able to filter the methanol molecules from the patient's blood.


Note: The treatment is similar to ethylene glycol poisoning.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources