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Alcohol, Kinetics and other features, Metabolism, Disulfiram like reaction…
Alcohol
Ethanol: it is a CNS depressant drug that can result in psychological as well as physical dependence.
It is an imperfect food because it lacks essential constituents and it cant be stored.
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Metabolism
Ethanol is metabolized to acetaldehyde by alcohol dehydrogenase
and finally to acetic acid by aldehyde dehydrogenase.
Disulfiram like reaction
Disulfiram(Antabuse)
and several drugs like chlorpropamide, cefoperazone, moxalactam, cefamandole, metronidazole, griseofulvin etc
causes inhibition of aldehyde dehydrogenase
resulting in accumulation of acetaldehyde.
Acetaldehyde may lead to severe distressing symptoms known as disulfiram like reaction.
Enzyme inducer
Chronic alcohol consumption induces microsomal enzymes.
More generation of toxic metabolite NAPQI of acetaminophen is responsible for increased risk of hepatotoxicity in alcoholics.
Alcohol increases the risk of hypoglycaemia in diabetic patients taking insulin and other oral hypoglycemic drugs.
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Disulfiram
Disulfiram can be used in psychologically dependent persons who are motivated to quit alcohol.
It is contraindicated in physically dependent individuals.
Disulfiram produces severe distressing symptoms
like flushing, headache, vomiting, visual disturbance and mental confusion after intake of alcohol.
These symptoms are due to accumulation of acetaldehyde.
Due to these symptoms, individuals resolution to quit alcohol is strengthened.
Topiramate and ondansetron can also decrease alcohol craving.
Methyl alcohol(methanol)
It is metabolized to formaldehyde by alcohol dehydrogenase
and finally to formic acid by aldehyde dehydrogenase.
Accumulation of formic acid may result in lactic acidosis(high anion gap metabolic acidosis), blindness and death.
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Important antidotes
Ethanol is useful because it competitively inhibits the conversion of methanol to formic acid.
Fomepizole can also be used in methanol poisoning because it is a specific inhibitor of alcohol dehydrogenase.
Folinic acid or folic acid can also be used because folate dependent systems are responsible for conversion of formic acid to CO2.
Ethylene glycol:
it is used as solvent and as an antifreeze in industry.
It is metabolized to glycolaldehyde and glycolic acid.
At toxic levels, it can cause renal tubular acidosis with excretion of oxalate crystals in the urine.
Fomepizole is the drug of choice for the treatment of ethylene glycol poisoning.