What should we do when someone is diagnosed with the methanol poisoning What harm does methanol cause on our body, such as the harm to some proteins? What first-aid measures should we take?
Methanol is highly toxic in humans. As little as 10 ml of pure methanol can destroy the optic nerve and cause permanent blindness, while 30 ml dose is fatal (Vale et al, 2007). However, its toxic effects take hours to come up after ingestion, and antidotes are often helpful in preventing permanent damage.
Methanol exerts its toxic effects by two main methods:
Much similar to ethanol, methanol is also a CNS depressant since it enhances the activity of inhibitory neurotransmitter GABA and also interferes with excitatory neurotransmitters.
When ingested, methanol is converted in liver first to methanal by alcohol dehydrogenase, and then to methanoic acid (or formic acid) by aldehyde dehydrogenase (Schep et al, 2009). Under cellular pH, formic acid exists as formate. Formate interferes with the mitochondrial enzyme cytochrome c oxidase, causing cellular hypoxia and metabolic acidosis (Liesivuori et al, 1991).
To prevent methanol toxicity, two kinds of antidotes are used:
Bicarbonate can alter the metabolic acidosis and potentially reverses the visual deficits.
Ethanol and fomepizole are also used as antidotes to methanol. Since the affinity of liver enzymes alcohol dehydrogenase and aldehyde dehydrogenase is about 10-20 times more for ethanol than methanol, ethanol can thus prevent (or at least delay) metabolism of methanol to formate. During this time, methanol can be removed from the body by kidneys or through dialysis. Fomepizole is also metabolized by the same enzymes, but ethanol is generally preferred due to high cost and low availability of fomepizole (Medscape). Thus, intravenous injections of ethanol can (under some circumstances) serve as a first-aid measure (although consulting a physician is always the best option).