General pharmacology: zero-order kinetics: 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 · General pharmacology: zero-order kinetics

Sample item

A man drinks heavily and his blood alcohol falls by roughly the same amount every hour, whether the level is high or low. Which kinetic pattern does this describe?

AZero-order elimination, a constant amount removed per unit time because enzymes are saturatedBFirst-order elimination, a constant fraction removed per unit timeCTwo-compartment redistribution with a rapid alpha phaseDFlip-flop kinetics caused by slow absorption

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

The answer and the reasoning

A. Zero-order elimination, a constant amount removed per unit time because enzymes are saturated

With zero-order (saturation) kinetics the elimination enzyme works at maximum capacity, so a fixed amount of drug is removed per hour regardless of concentration. Alcohol, phenytoin at higher doses and high-dose aspirin behave this way, and a small dose increase can produce a disproportionate rise in level.

Option by option

A. Zero-order elimination, a constant amount removed per unit time because enzymes are saturated (correct)
Correct. A constant amount per hour at any concentration is the definition of zero-order kinetics.
B. First-order elimination, a constant fraction removed per unit time
Under first-order kinetics the amount eliminated falls as the concentration falls, since a fixed fraction is cleared.
C. Two-compartment redistribution with a rapid alpha phase
Redistribution describes a fast initial fall between compartments, not a steady linear decline.
D. Flip-flop kinetics caused by slow absorption
Flip-flop kinetics refers to absorption being slower than elimination, which does not explain a constant hourly fall.

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, Zero-order elimination, a constant amount removed per unit time because enzymes are saturated. With zero-order (saturation) kinetics the elimination enzyme works at maximum capacity, so a fixed amount of drug is removed per hour regardless of concentration.

Why is "First-order elimination, a constant fraction removed per unit time" not the answer?

Under first-order kinetics the amount eliminated falls as the concentration falls, since a fixed fraction is cleared.

Why is "Two-compartment redistribution with a rapid alpha phase" not the answer?

Redistribution describes a fast initial fall between compartments, not a steady linear decline.

Why is "Flip-flop kinetics caused by slow absorption" not the answer?

Flip-flop kinetics refers to absorption being slower than elimination, which does not explain a constant hourly fall.

What concept does this question test?

It tests General pharmacology: zero-order kinetics in Pharmacology. Alcohol, phenytoin at higher doses and high-dose aspirin behave this way, and a small dose increase can produce a disproportionate rise in level.

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 General pharmacology: zero-order kinetics?

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.