Vitamins and minerals: niacin flushing: practice question

A Biochemistry 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

Biochemistry · Vitamins and minerals: niacin flushing

Sample item

A man with dyslipidaemia is started on nicotinic acid in pharmacological doses and complains of intense facial flushing and warmth. Which mediator accounts for the flushing, and which simple measure reduces it?

ASerotonin, reduced by prior ondansetronBHistamine, reduced by prior atenololCBradykinin, reduced by prior enalaprilDProstaglandin D2, reduced by prior aspirin

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

The answer and the reasoning

D. Prostaglandin D2, reduced by prior aspirin

Nicotinic acid acts on GPR109A in dermal Langerhans cells, causing release of prostaglandin D2 that dilates skin vessels. Aspirin taken before the dose blunts the flushing. Other adverse effects include hyperglycaemia, hyperuricaemia and hepatotoxicity.

Option by option

A. Serotonin, reduced by prior ondansetron
Serotonin is not the mediator of this flush.
B. Histamine, reduced by prior atenolol
Histamine is not the main mediator, and a beta blocker does not prevent the flush.
C. Bradykinin, reduced by prior enalapril
Bradykinin accumulation causes ACE inhibitor cough, not niacin flushing.
D. Prostaglandin D2, reduced by prior aspirin (correct)
Correct. Prostaglandin D2 mediates the flush and aspirin blocks its synthesis.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Prostaglandin D2, reduced by prior aspirin. Nicotinic acid acts on GPR109A in dermal Langerhans cells, causing release of prostaglandin D2 that dilates skin vessels.

Why is "Serotonin, reduced by prior ondansetron" not the answer?

Serotonin is not the mediator of this flush.

Why is "Histamine, reduced by prior atenolol" not the answer?

Histamine is not the main mediator, and a beta blocker does not prevent the flush.

Why is "Bradykinin, reduced by prior enalapril" not the answer?

Bradykinin accumulation causes ACE inhibitor cough, not niacin flushing.

What concept does this question test?

It tests Vitamins and minerals: niacin flushing in Biochemistry. Aspirin taken before the dose blunts the flushing. Other adverse effects include hyperglycaemia, hyperuricaemia and hepatotoxicity.

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 Vitamins and minerals: niacin flushing?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.