Determination of methanol

Methanol (CH3OH _, wood alcohol, methyl alcohol) can be absorbed through the skin, respiratory tract, or gastrointestinal tract. When methanol enters the gastrointestinal tract, it is rapidly absorbed and distributed in body fluids. The main mechanism of methanol elimination in humans is oxidation to formaldehyde, formic acid, and CO2 _. Metabolism occurs in the liver with the participation of alcohol dehydrogenase. The particular sensitivity of humans to the toxic effects of methanol is associated with folate-dependent formate production, and not with methanol itself or the intermediate metabolic product, formaldehyde. Ethanol has a higher affinity for alcohol dehydrogenase than methanol. Therefore, saturation of the enzyme with ethanol can reduce formate formation and is often used to treat acute methanol intoxication. The alcohol dehydrogenase inhibitor methylpyrazole, alone or in combination with ethanol, has a good therapeutic effect in methanol and ethylene glycol poisoning.

Severe methanol poisoning is usually observed in people suffering from alcoholism and may not be recognized until characteristic symptoms appear, the most important and earliest of which is visual impairment ("snowfall, blizzard picture"). In severe cases, the patient's breath may smell formaldehyde, and the urine may also smell the same. The lethal dose of methanol when taken orally is from 60 to 250 ml, an average of 100 ml (without prior alcohol intake), although in some cases even 15 ml may be fatal.

If methanol poisoning is suspected, its concentration in the blood should be determined as soon as possible. However, the concentration of formate in the blood is a more accurate indicator of the severity of poisoning. A methanol concentration in the blood of 30 mg% or higher (formate - 3.6 mg% or higher) is considered toxic, and more than 80 mg% is considered lethal. Additional laboratory data indicating poisoning include metabolic acidosis with an increase in the anion gap and osmolarity. A decrease in serum bicarbonate is also a characteristic sign of severe methanol poisoning and an indication for treatment with ethanol.

Before starting treatment, in addition to the concentration of methanol, it is necessary to determine the level of ethanol and ethylene glycol in the blood.

Ethanol is used to treat poisoning in cases where the methanol concentration in the blood exceeds 20 mg% or when metabolic acidosis with an increased anion gap develops. Ethanol slows down the metabolism of methanol, reducing its toxicity. The initial dose of ethanol is 600 mg/kg, the maintenance dose is 100-150 mg/kg. When using ethanol in treatment, it is necessary to achieve its concentration in the blood of 100-150 mg%, and maintain this level until the methanol concentration falls below 10 mg% (formate below 1.2 mg%). If it is impossible to determine the methanol concentration, ethanol is prescribed for at least 5 days for patients who do not undergo hemodialysis, and 1 day for patients on dialysis.

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