Antiretrovirals: ritonavir boosting: 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 · Antiretrovirals: ritonavir boosting

Sample item

Why is low-dose ritonavir added to other protease inhibitors such as lopinavir or atazanavir?

AIt inhibits CYP3A4, boosting the plasma level of the partner drugBIt induces CYP3A4 to reduce toxicityCIt blocks viral entryDIt adds antiviral potency against integrase

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

The answer and the reasoning

A. It inhibits CYP3A4, boosting the plasma level of the partner drug

Ritonavir is a potent CYP3A4 inhibitor, so low doses are used as a pharmacokinetic enhancer to increase levels and half-life of other protease inhibitors. This causes many interactions, including with statins, ergots and sildenafil. Protease inhibitors also cause lipodystrophy and insulin resistance.

Option by option

A. It inhibits CYP3A4, boosting the plasma level of the partner drug (correct)
Correct. CYP3A4 inhibition boosts partner levels.
B. It induces CYP3A4 to reduce toxicity
It inhibits rather than induces CYP3A4.
C. It blocks viral entry
Entry blockade is the action of maraviroc and enfuvirtide.
D. It adds antiviral potency against integrase
Its role is pharmacokinetic and not integrase inhibition.

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, It inhibits CYP3A4, boosting the plasma level of the partner drug. Ritonavir is a potent CYP3A4 inhibitor, so low doses are used as a pharmacokinetic enhancer to increase levels and half-life of other protease inhibitors.

Why is "It induces CYP3A4 to reduce toxicity" not the answer?

It inhibits rather than induces CYP3A4.

Why is "It blocks viral entry" not the answer?

Entry blockade is the action of maraviroc and enfuvirtide.

Why is "It adds antiviral potency against integrase" not the answer?

Its role is pharmacokinetic and not integrase inhibition.

What concept does this question test?

It tests Antiretrovirals: ritonavir boosting in Pharmacology. This causes many interactions, including with statins, ergots and sildenafil. Protease inhibitors also cause lipodystrophy and insulin resistance.

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 Antiretrovirals: ritonavir boosting?

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.