Toxicology and antidotes: zinc in Wilson disease: 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 and antidotes: zinc in Wilson disease

Sample item

A patient with Wilson disease has been decoppered and is on maintenance therapy with zinc acetate. How does zinc reduce body copper?

AIt blocks hepatic copper uptake competitivelyBIt chelates copper in blood for urinary excretionCIt increases biliary copper excretion by upregulating ATP7BDIt induces intestinal metallothionein, which binds copper and blocks its absorption

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

The answer and the reasoning

D. It induces intestinal metallothionein, which binds copper and blocks its absorption

Zinc induces metallothionein in enterocytes. Metallothionein binds copper more avidly than zinc, so copper is trapped in the cell and lost when the cell is shed. Chelators such as penicillamine and trientine instead mobilise copper for urinary excretion.

Option by option

A. It blocks hepatic copper uptake competitively
Zinc acts at the intestine and not by blocking hepatic uptake.
B. It chelates copper in blood for urinary excretion
Chelation for urinary excretion is the action of penicillamine and trientine.
C. It increases biliary copper excretion by upregulating ATP7B
ATP7B is the defective gene in Wilson disease, and zinc does not correct it.
D. It induces intestinal metallothionein, which binds copper and blocks its absorption (correct)
Correct. Metallothionein induction traps dietary copper in enterocytes.

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 D, It induces intestinal metallothionein, which binds copper and blocks its absorption. Zinc induces metallothionein in enterocytes.

Why is "It blocks hepatic copper uptake competitively" not the answer?

Zinc acts at the intestine and not by blocking hepatic uptake.

Why is "It chelates copper in blood for urinary excretion" not the answer?

Chelation for urinary excretion is the action of penicillamine and trientine.

Why is "It increases biliary copper excretion by upregulating ATP7B" not the answer?

ATP7B is the defective gene in Wilson disease, and zinc does not correct it.

What concept does this question test?

It tests Toxicology and antidotes: zinc in Wilson disease in Pharmacology. Metallothionein binds copper more avidly than zinc, so copper is trapped in the cell and lost when the cell is shed. Chelators such as penicillamine and trientine instead mobilise copper for urinary excretion.

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 and antidotes: zinc in Wilson disease?

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.