Toxicology: Gloriosa superba colchicine poisoning: practice question

A Pharmacology 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.

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Pharmacology · Toxicology: Gloriosa superba colchicine poisoning

Sample item

A farm worker in Tamil Nadu mistakes tubers of the glory lily (Gloriosa superba) for a yam and eats them. After vomiting and profuse diarrhoea, he develops leukopenia and a falling platelet count over the next week, followed by hair loss. Which mechanism underlies the toxicity?

AInhibition of the sodium-potassium ATPase pumpBInhibition of RNA polymerase IICBinding of colchicine to tubulin, preventing microtubule polymerisation and arresting mitosisDBlockade of muscarinic receptors

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

The answer and the reasoning

C. Binding of colchicine to tubulin, preventing microtubule polymerisation and arresting mitosis

Gloriosa superba contains colchicine and related alkaloids, which bind tubulin and prevent microtubule assembly, arresting dividing cells in metaphase. Rapidly dividing tissues such as gut mucosa, marrow and hair follicles are affected, giving early gastroenteritis and later pancytopenia and alopecia. There is no widely available specific antidote, so care is supportive with fluids, electrolytes and marrow support.

Option by option

A. Inhibition of the sodium-potassium ATPase pump
Sodium-potassium ATPase inhibition is the action of cardiac glycosides such as yellow oleander and digoxin.
B. Inhibition of RNA polymerase II
RNA polymerase II inhibition is the action of amatoxins from Amanita phalloides, which cause hepatic failure.
C. Binding of colchicine to tubulin, preventing microtubule polymerisation and arresting mitosis (correct)
Tubulin binding arrests mitosis, which explains the gut, marrow and hair follicle toxicity.
D. Blockade of muscarinic receptors
Muscarinic blockade causes dry mouth, mydriasis and tachycardia, not marrow suppression.

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.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Binding of colchicine to tubulin, preventing microtubule polymerisation and arresting mitosis. Gloriosa superba contains colchicine and related alkaloids, which bind tubulin and prevent microtubule assembly, arresting dividing cells in metaphase.

Why is "Inhibition of the sodium-potassium ATPase pump" not the answer?

Sodium-potassium ATPase inhibition is the action of cardiac glycosides such as yellow oleander and digoxin.

Why is "Inhibition of RNA polymerase II" not the answer?

RNA polymerase II inhibition is the action of amatoxins from Amanita phalloides, which cause hepatic failure.

Why is "Blockade of muscarinic receptors" not the answer?

Muscarinic blockade causes dry mouth, mydriasis and tachycardia, not marrow suppression.

What concept does this question test?

It tests Toxicology: Gloriosa superba colchicine poisoning in Pharmacology. Rapidly dividing tissues such as gut mucosa, marrow and hair follicles are affected, giving early gastroenteritis and later pancytopenia and alopecia. There is no widely available specific antidote, so care is supportive with fluids, electrolytes and marrow support.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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: Gloriosa superba colchicine poisoning?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.