All of the following are true about methanol poisoning except: (AIIMS November 2013, May 2013)
Correct Answer: Fomepizole is a competitive inhibitor of aldehyde dehydrogenase
Description: Ans. a. Fomepizole is a competitive inhibitor of aldehyde dehydrogenase (Ref: Reddy 33/e p582, 3lst/387; KDT 6/e p395)Fomepizole is a specific inhibitor of alcohol dehydrogenase, not the aldehyde dehydrogenase.Fomepizole:Fomepizole (4-methylpyrazole) is a specific inhibitor of alcohol dehydrogenase- retards methanol metabolismLoading dose is 15 mg/Kg IV followed by 10 mg/kg every 12 hours till serum methanol falls below 20 g/dL, has been found effective and safe.Minimum lethal dose of methanol is 1.25ml/kg body weight:Minimum lethal dose of methanol is 0.3-1.0 gm/kgFormic acid is mainly responsible for toxicity:In methyl alcohol poisoning there is CNS depression, cardiac depression and optic nerve atrophy. These effects are produced due to Formaldehyde and formic acid.The specific toxicity of formic acid is retinal damage.Methanol causes snow field vision:Methanol causes snowfield vision, blurred vision, decreased visual acuity, diplopia and photopia Methyl Alcohol Poisoning* Can be present in contaminated country liquorQ, used to denature ethanol.* Metabolized to formaldehyde and formic acidQ by alcohol and aldehyde dehydrogenase respectively.* Is a CNS depressant and toxicity is mainly due to formic aeidQ.Clinical Presentation:* Symptoms may appear with in an hourQ but are commonly delayed* Nausea, VomitingQ, Dizziness, Headache, Abdomen pain.* Temporary blindness to optic atrophyQ. Convulsions, ComaFatal dose: 60-200 mIFatal period: 24-36 hours, may be delayed for 2-4 daysInvestigation: Serum Methanol and formate levelTreatment:* Gastric lavage (treatment of choice)* NaHCO3 for acidosis and Treatment of seizures* EthanolQ or Fomepizole (4-Methly pyrazole) therapy in:1. Methanol cone. > 6 mmol/L2. Increased anion gap acidosis3. Visual symptomsQ
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