Pharmacokinetics: 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 · Pharmacokinetics

Sample item

A drug has an apparent volume of distribution of 40 L and an oral bioavailability of 50 percent. What oral loading dose is needed to achieve a plasma concentration of 10 mg/L?

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

The answer and the reasoning

B. 800 mg

Loading dose equals target concentration multiplied by volume of distribution, divided by bioavailability. Here 10 mg/L times 40 L gives 400 mg in the body, and dividing by 0.5 gives 800 mg orally.

Option by option

  • A. 400 mg

    400 mg would be adequate only for intravenous dosing, as it ignores incomplete absorption.

  • B. 800 mg (correct)

    Correct. 10 times 40 divided by 0.5 equals 800 mg.

  • C. 1600 mg

    1600 mg would correspond to a bioavailability of 25 percent, not 50 percent.

  • D. 200 mg

    200 mg results from multiplying by the bioavailability instead of dividing by it.

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.

More Pharmacology questions

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, 800 mg. Loading dose equals target concentration multiplied by volume of distribution, divided by bioavailability.

Why is "400 mg" not the answer?

400 mg would be adequate only for intravenous dosing, as it ignores incomplete absorption.

Why is "1600 mg" not the answer?

1600 mg would correspond to a bioavailability of 25 percent, not 50 percent.

Why is "200 mg" not the answer?

200 mg results from multiplying by the bioavailability instead of dividing by it.

What concept does this question test?

It tests Pharmacokinetics in Pharmacology. Here 10 mg/L times 40 L gives 400 mg in the body, and dividing by 0.5 gives 800 mg orally.

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 Pharmacokinetics?

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.