Endocrine drugs: phosphate binder choice in dialysis: 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 · Endocrine drugs: phosphate binder choice in dialysis

Sample item

A haemodialysis patient taking calcium carbonate has a serum calcium of 11.0 mg/dL and a phosphate of 7.5 mg/dL. Which change is most appropriate?

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

The answer and the reasoning

B. Switch to sevelamer

Sevelamer is a non-absorbed, calcium-free polymer that binds dietary phosphate in the gut and also lowers LDL cholesterol. It lowers phosphate without adding to calcium load. Lanthanum is another non-calcium binder. Aluminium hydroxide causes aluminium toxicity with long use.

Option by option

  • A. Add long-term aluminium hydroxide

    Long-term aluminium causes encephalopathy, bone disease and anaemia.

  • B. Switch to sevelamer (correct)

    Correct. A non-calcium binder lowers phosphate without further raising calcium.

  • C. Add calcitriol

    Calcitriol increases gut absorption of both calcium and phosphate, and would worsen both.

  • D. Increase the calcium carbonate dose

    More calcium carbonate would worsen the hypercalcaemia.

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.

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Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, Switch to sevelamer. Sevelamer is a non-absorbed, calcium-free polymer that binds dietary phosphate in the gut and also lowers LDL cholesterol.

Why is "Add long-term aluminium hydroxide" not the answer?

Long-term aluminium causes encephalopathy, bone disease and anaemia.

Why is "Add calcitriol" not the answer?

Calcitriol increases gut absorption of both calcium and phosphate, and would worsen both.

Why is "Increase the calcium carbonate dose" not the answer?

More calcium carbonate would worsen the hypercalcaemia.

What concept does this question test?

It tests Endocrine drugs: phosphate binder choice in dialysis in Pharmacology. It lowers phosphate without adding to calcium load. Lanthanum is another non-calcium binder. Aluminium hydroxide causes aluminium toxicity with long use.

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 Endocrine drugs: phosphate binder choice in dialysis?

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.