Local anaesthetics: adrenaline addition: 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 · Local anaesthetics: adrenaline addition

Sample item

Why is adrenaline added to lidocaine for infiltration, and where must the mixture be avoided?

AIt increases systemic absorptionBIt reduces the potency of the blockCIt speeds metabolism of lidocaine and is safe in fingersDVasoconstriction prolongs the block and reduces toxicity, but it is avoided in end-arterial regions such as fingers and penis

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

The answer and the reasoning

D. Vasoconstriction prolongs the block and reduces toxicity, but it is avoided in end-arterial regions such as fingers and penis

Adrenaline reduces blood flow, delaying absorption and thus prolonging the duration, lowering peak plasma level and giving a drier field. In end-arterial areas, vasoconstriction may produce ischaemic necrosis.

Option by option

A. It increases systemic absorption
It decreases systemic absorption.
B. It reduces the potency of the block
It increases the duration of action.
C. It speeds metabolism of lidocaine and is safe in fingers
It does not hasten metabolism and is unsafe in fingers.
D. Vasoconstriction prolongs the block and reduces toxicity, but it is avoided in end-arterial regions such as fingers and penis (correct)
Correct. Longer action, but risk of ischaemia in end arteries.

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 D, Vasoconstriction prolongs the block and reduces toxicity, but it is avoided in end-arterial regions such as fingers and penis. Adrenaline reduces blood flow, delaying absorption and thus prolonging the duration, lowering peak plasma level and giving a drier field.

Why is "It increases systemic absorption" not the answer?

It decreases systemic absorption.

Why is "It reduces the potency of the block" not the answer?

It increases the duration of action.

Why is "It speeds metabolism of lidocaine and is safe in fingers" not the answer?

It does not hasten metabolism and is unsafe in fingers.

What concept does this question test?

It tests Local anaesthetics: adrenaline addition in Pharmacology. In end-arterial areas, vasoconstriction may produce ischaemic necrosis.

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 Local anaesthetics: adrenaline addition?

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.