Question:
Many people have consumed contaminated alcohol and present with abdominal pain, confusion, decreased vision. Methyl alcohol conc detected as 20 mg %. On assessment which metabolites will be found
Many people have consumed contaminated alcohol and present with abdominal pain, confusion, decreased vision. Methyl alcohol conc detected as 20 mg %. On assessment which metabolites will be found
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Methanol → formaldehyde → formic acid; the resulting mitochondrial block also raises one more common acid. (Oxalic/glycolic acids belong to ethylene glycol.)
Updated On: Aug 27, 2026
- Formic acid & lactic acid
- Glycolic acid & oxalic acid
- Oxalic acid & formic acid
- Glyoxylic acid & formic acid
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The Correct Option is A
Solution and Explanation
Step 1: Identify the toxin and clinical picture. A cluster of people drinking contaminated (illicit) alcohol with abdominal pain, confusion and decreased vision, plus a measured methyl alcohol (methanol) level of 20 mg%, is methanol poisoning. The visual loss is the hallmark.
Step 2: Recall the metabolic pathway of methanol. Methanol is oxidised in the liver:
\[\text{Methanol} \xrightarrow{\text{alcohol dehydrogenase}} \text{Formaldehyde} \xrightarrow{\text{aldehyde dehydrogenase}} \text{Formic acid}\]
The toxic end-metabolite is formic acid (formate), which inhibits cytochrome oxidase, damages the optic nerve/retina and produces a severe high-anion-gap metabolic acidosis.
Step 3: Account for the second acid. The accumulating formate impairs mitochondrial respiration; tissue hypoxia and anaerobic glycolysis then generate lactic acid. So both formic acid and lactic acid build up and together drive the high-anion-gap acidosis seen in methanol poisoning. Hence the metabolites detected are formic acid and lactic acid.
Step 4: Eliminate the distractors. Glycolic acid and oxalic acid (B), oxalic acid and formic acid (C) and glyoxylic acid and formic acid (D) all involve glycolic/oxalic/glyoxylic acids - these are products of ETHYLENE GLYCOL metabolism, not methanol. Ethylene glycol is metabolised through glycolaldehyde → glycolic acid → glyoxylic acid → oxalic acid (causing calcium-oxalate crystals and renal failure). Since the toxin here is methanol, oxalic/glycolic/glyoxylic acids do not apply.
Final answer: A - Formic acid & lactic acid.
Step 2: Recall the metabolic pathway of methanol. Methanol is oxidised in the liver:
\[\text{Methanol} \xrightarrow{\text{alcohol dehydrogenase}} \text{Formaldehyde} \xrightarrow{\text{aldehyde dehydrogenase}} \text{Formic acid}\]
The toxic end-metabolite is formic acid (formate), which inhibits cytochrome oxidase, damages the optic nerve/retina and produces a severe high-anion-gap metabolic acidosis.
Step 3: Account for the second acid. The accumulating formate impairs mitochondrial respiration; tissue hypoxia and anaerobic glycolysis then generate lactic acid. So both formic acid and lactic acid build up and together drive the high-anion-gap acidosis seen in methanol poisoning. Hence the metabolites detected are formic acid and lactic acid.
Step 4: Eliminate the distractors. Glycolic acid and oxalic acid (B), oxalic acid and formic acid (C) and glyoxylic acid and formic acid (D) all involve glycolic/oxalic/glyoxylic acids - these are products of ETHYLENE GLYCOL metabolism, not methanol. Ethylene glycol is metabolised through glycolaldehyde → glycolic acid → glyoxylic acid → oxalic acid (causing calcium-oxalate crystals and renal failure). Since the toxin here is methanol, oxalic/glycolic/glyoxylic acids do not apply.
Final answer: A - Formic acid & lactic acid.
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