Methanol, which is also called wood spirit is widely used in the production of formaldehyde , and is also used to denature alcohol. It is used in antifreeze solutions, paints, duplicating fluids, paint removes and varnishes and as a solvent.

From time to time we hear of deaths and blindness in those who survive after consuming kasippu containing methanol in significant concentrations. A few days ago the news media reported a number of deaths and permanent blindness in some of those who survived after consuming kasippu containing methanol, ingestion of as little as 10ml of methanol can cause permanent blindness and 30 ml of methanol is potentially fatal. Toxicity also can occur due to inhalation or absorption of methanol through the skin.

Methylated spirits consist of 5 percent methanol and 95 percent ethanol (ethyl alcohol) and contrary to popular opinion toxicity of methylated spirit is mainly due to the presence of ethanol.

In humans, methanol is metabolised by an enzyme called alcohol dehydrogenase and catalyse enzyme systems, to formaldehyde and formic acid and the patients get acidosis due to concentration of formate. Depression of liver enzyme systems inhibit glucose production by the liver (gluconeogenesis) and lactate so produced make the acidosis worse. It is not certain whether the blindness is due to local formation of formaldehyde in the retina of the eye or due to damage to the optic nerve of the eye as a result of enzymes activated by the formate. Methanol also interferes with the utilisation of vitamin A in the eye.

The patients who come to the hospital may be suffering from mild and transient inebriation and drowsiness when methanol is ingested by itself. After a latent period of 8 to 36 hrs nausea, vomiting, abdominal pain, headache, dizziness and coma supervene. Blurred vision and diminished visual activity may occur and the pupils of the eyes get dilated in people who become permanently blind.

In severe cases metabolic acidosis accompanied by high blood sugar occurs. A blood methanol level greater than 500mg/L confirms serious methanol poisoning.

If the patient is brought to the hospital in the first two hours of the poisoning , doctors give gastric lavage. If the patient arrives at the hospital after two hours with acidosis, it can be corrected by giving bicarbonate. Correction of blood pressure is important and it is advisable to keep the patients in the intensive care unit (ICU)

Early cases are treated with alcohol (ethyl alcohol or ethanol), but , giving alcohol is useless if the patient arrives late. If the patient comes after about four hours it is not a wise move to give ethanol as, the acidosis may get worse. If the patient comes in the first two hours , physicians usually give about 50gm of ethanol in the form of arrack or whiskey or gin and this should be followed by an infusion of 10 to 12 gm of ethanol.

As stated earlier, ideally all patients with methanol poisoning should be managed in an intensive care unit where serum ethanol and methanol levels can be checked from time to time. In patients who have ingested large amounts of methanol, dialysis (haemodialysis or peritoneal dialysis) should be done, every two to three hours so that toxicity to the optic nerve can be prevented.