Toxicology: oxalic acid poisoning: practice question

A Forensic Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Forensic Medicine · Toxicology: oxalic acid poisoning

Sample item

A man drinks a rust-removing solution and develops perioral numbness, carpopedal spasm and a prolonged QT interval. Urine microscopy shows envelope-shaped crystals. Which is the most appropriate specific measure?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Intravenous calcium gluconate

Oxalic acid binds ionised calcium to form insoluble calcium oxalate, causing hypocalcaemia with tetany and arrhythmias, and the crystals damage the kidney. Intravenous calcium gluconate corrects the hypocalcaemia, and fluids protect the kidney. Emesis is avoided because the acid is corrosive.

Option by option

  • A. Intravenous sodium thiosulphate

    Thiosulphate is used for cyanide poisoning and does not bind oxalate.

  • B. Intravenous dimercaprol

    Dimercaprol is a chelator for arsenic and mercury and has no action on oxalate.

  • C. Oral activated charcoal

    Charcoal does not adsorb corrosive acids and adds the risk of impeding endoscopy.

  • D. Intravenous calcium gluconate (correct)

    Correct. Calcium replacement treats the hypocalcaemic tetany and QT prolongation.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Forensic Medicine questions

Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is D, Intravenous calcium gluconate. Oxalic acid binds ionised calcium to form insoluble calcium oxalate, causing hypocalcaemia with tetany and arrhythmias, and the crystals damage the kidney.

Why is "Intravenous sodium thiosulphate" not the answer?

Thiosulphate is used for cyanide poisoning and does not bind oxalate.

Why is "Intravenous dimercaprol" not the answer?

Dimercaprol is a chelator for arsenic and mercury and has no action on oxalate.

Why is "Oral activated charcoal" not the answer?

Charcoal does not adsorb corrosive acids and adds the risk of impeding endoscopy.

What concept does this question test?

It tests Toxicology: oxalic acid poisoning in Forensic Medicine. Intravenous calcium gluconate corrects the hypocalcaemia, and fluids protect the kidney. Emesis is avoided because the acid is corrosive.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Toxicology: oxalic acid poisoning?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.