Chemotherapy: ivermectin: 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 · Chemotherapy: ivermectin

Sample item

A family has an outbreak of scabies with intense nocturnal itching and burrows between the fingers. Oral ivermectin is chosen. What is its mechanism of action?

ABinding to glutamate-gated chloride channels, causing paralysis of the parasiteBInhibition of acetylcholinesterase in the parasiteCAgonism at parasite nicotinic acetylcholine receptors causing spastic paralysisDInhibition of tubulin polymerisation in parasite cells

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

The answer and the reasoning

A. Binding to glutamate-gated chloride channels, causing paralysis of the parasite

Ivermectin potentiates glutamate-gated chloride channels in invertebrate nerve and muscle cells, causing hyperpolarisation and flaccid paralysis. It is used for strongyloidiasis, onchocerciasis, filariasis and scabies. It is not used in young children under 15 kg or in pregnancy.

Option by option

A. Binding to glutamate-gated chloride channels, causing paralysis of the parasite (correct)
Correct. Chloride influx paralyses the mite or worm.
B. Inhibition of acetylcholinesterase in the parasite
Cholinesterase inhibition is the action of organophosphates.
C. Agonism at parasite nicotinic acetylcholine receptors causing spastic paralysis
Pyrantel pamoate acts as an agonist at nicotinic receptors.
D. Inhibition of tubulin polymerisation in parasite cells
Tubulin inhibition is the action of albendazole and mebendazole.

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 A, Binding to glutamate-gated chloride channels, causing paralysis of the parasite. Ivermectin potentiates glutamate-gated chloride channels in invertebrate nerve and muscle cells, causing hyperpolarisation and flaccid paralysis.

Why is "Inhibition of acetylcholinesterase in the parasite" not the answer?

Cholinesterase inhibition is the action of organophosphates.

Why is "Agonism at parasite nicotinic acetylcholine receptors causing spastic…" not the answer?

Pyrantel pamoate acts as an agonist at nicotinic receptors.

Why is "Inhibition of tubulin polymerisation in parasite cells" not the answer?

Tubulin inhibition is the action of albendazole and mebendazole.

What concept does this question test?

It tests Chemotherapy: ivermectin in Pharmacology. It is used for strongyloidiasis, onchocerciasis, filariasis and scabies. It is not used in young children under 15 kg or in pregnancy.

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 Chemotherapy: ivermectin?

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.