Question:medium
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: Jun 22, 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
Pathway-first reasoning.
The scenario - multiple victims of spurious liquor with confusion, abdominal pain and, crucially, loss of vision, with a measured methanol level - fixes the poison as methanol. Decide the metabolites by tracing methanol's biotransformation, not the other alcohols'.
Methanol metabolism: Hepatic alcohol dehydrogenase converts methanol to formaldehyde, and aldehyde dehydrogenase then converts formaldehyde to formic acid. Formic acid (formate) is the culprit metabolite: it blocks cytochrome-c oxidase, poisons the optic nerve (explaining the visual symptoms) and causes a severe metabolic acidosis.
The accompanying acid: Because formate inhibits the mitochondrial electron-transport chain, cells switch to anaerobic metabolism and pour out lactic acid. So the two acids that accumulate - and that one would find on assessment - are formic acid and lactic acid, together producing the high anion gap.
Distinguishing from ethylene glycol: The other three options list glycolic, oxalic or glyoxylic acid. These belong to ethylene glycol, which is metabolised to glycolaldehyde $\rightarrow$ glycolic acid $\rightarrow$ glyoxylic acid $\rightarrow$ oxalic acid; ethylene glycol classically causes calcium-oxalate crystalluria, hypocalcaemia and renal failure - a different toxidrome from methanol's visual loss. Since this patient was poisoned by methanol, those acids are not the answer.
Hence the metabolites found are formic acid and lactic acid.
Answer: A (Formic acid & lactic acid).
The scenario - multiple victims of spurious liquor with confusion, abdominal pain and, crucially, loss of vision, with a measured methanol level - fixes the poison as methanol. Decide the metabolites by tracing methanol's biotransformation, not the other alcohols'.
Methanol metabolism: Hepatic alcohol dehydrogenase converts methanol to formaldehyde, and aldehyde dehydrogenase then converts formaldehyde to formic acid. Formic acid (formate) is the culprit metabolite: it blocks cytochrome-c oxidase, poisons the optic nerve (explaining the visual symptoms) and causes a severe metabolic acidosis.
The accompanying acid: Because formate inhibits the mitochondrial electron-transport chain, cells switch to anaerobic metabolism and pour out lactic acid. So the two acids that accumulate - and that one would find on assessment - are formic acid and lactic acid, together producing the high anion gap.
Distinguishing from ethylene glycol: The other three options list glycolic, oxalic or glyoxylic acid. These belong to ethylene glycol, which is metabolised to glycolaldehyde $\rightarrow$ glycolic acid $\rightarrow$ glyoxylic acid $\rightarrow$ oxalic acid; ethylene glycol classically causes calcium-oxalate crystalluria, hypocalcaemia and renal failure - a different toxidrome from methanol's visual loss. Since this patient was poisoned by methanol, those acids are not the answer.
Hence the metabolites found are formic acid and lactic acid.
Answer: A (Formic acid & lactic acid).
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