Determination of methanol
Last reviewed: 23.04.2024
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Methanol (CH 3 OH, wood alcohol, methyl alcohol) can be absorbed through the skin, respiratory tract or gastrointestinal tract. When ingested in the gastrointestinal tract, methanol is rapidly absorbed and distributed in the body fluids. The main mechanism for eliminating methanol in humans is oxidation to formaldehyde, formic acid and CO 2. Metabolism occurs in the liver with the participation of alcohol dehydrogenase. The special sensitivity of a person to the toxic effect of methanol is associated with folate-dependent production of formate, and not with methanol itself or an intermediate product of metabolism - formaldehyde. Ethanol has a higher affinity for alcohol dehydrogenase than methanol. Therefore, saturation of the enzyme with ethanol can reduce the formation of formate 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 persons with alcoholism and may not be recognized until characteristic symptoms appear, the most important and early of which is visual disturbance ("snowfall pattern, blizzards"). In severe cases, the odor of formaldehyde can be felt when the patient is breathing, the same odor can be produced by urine. The lethal dose of methanol when ingested is from 60 to 250 ml, an average of 100 ml (without prior intake of alcohol), although in some cases the intake of even 15 ml can be fatal.
If suspected of methanol poisoning, it is necessary to determine its concentration in the blood as soon as possible. At the same time, the concentration of formate in the blood is a more accurate indicator of the severity of the poisoning. Toxic is the concentration of methanol in the blood of 30 mg% and higher (formate - 3.6 mg% and more), the lethal - more than 80 mg%. Additional laboratory data suggesting the poisoning is metabolic acidosis with an increase in the anion interval and osmolarity. Reduction of serum bicarbonate is also a characteristic sign of severe methanol poisoning and an indication for the treatment of ethanol.
Before starting treatment in the blood, in addition to the concentration of methanol, it is necessary to determine the level of ethanol and ethylene glycol.
Ethanol for the treatment of poisoning is used in cases where the concentration of methanol in the blood exceeds 20 mg% or when metabolic acidosis develops with an increased anion interval. Ethanol slows the metabolism of methanol, reducing its toxicity. The initial dose of ethanol is 600 mg / kg, supporting - 100-150 mg / kg. When used in the treatment of ethanol, it is necessary to ensure that its concentration in the blood is 100-150 mg%, and maintain this level until the methanol concentration is below 10 mg% (formate below 1.2 mg%). If it is not possible to determine the concentration of methanol, ethanol is prescribed for at least 5 days to patients who do not undergo hemodialysis, and 1 day to patients with dialysis.
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