CNS drugs and antiepileptics: ropivacaine versus bupivacaine: 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 · CNS drugs and antiepileptics: ropivacaine versus bupivacaine

Sample item

A labouring woman needs prolonged epidural analgesia by continuous infusion, and the anaesthetist chooses ropivacaine over bupivacaine. What is the main reason?

AAction on potassium channels instead of sodium channelsBHigher potency allowing a smaller volumeCEster linkage with rapid plasma hydrolysisDLower cardiotoxicity and less motor block

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

The answer and the reasoning

D. Lower cardiotoxicity and less motor block

Ropivacaine is the pure S-enantiomer of a propyl analogue of bupivacaine. It is less lipophilic, so it produces less motor block and has a lower risk of cardiac toxicity if absorbed or injected intravascularly. Its potency is a little lower than that of bupivacaine.

Option by option

A. Action on potassium channels instead of sodium channels
Both drugs block voltage-gated sodium channels.
B. Higher potency allowing a smaller volume
Ropivacaine is slightly less potent than bupivacaine.
C. Ester linkage with rapid plasma hydrolysis
Ropivacaine is an amide, and ester hydrolysis in plasma is a feature of chloroprocaine.
D. Lower cardiotoxicity and less motor block (correct)
Correct. Lower cardiotoxicity and less motor block make it suitable for prolonged infusion.

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, Lower cardiotoxicity and less motor block. Ropivacaine is the pure S-enantiomer of a propyl analogue of bupivacaine.

Why is "Action on potassium channels instead of sodium channels" not the answer?

Both drugs block voltage-gated sodium channels.

Why is "Higher potency allowing a smaller volume" not the answer?

Ropivacaine is slightly less potent than bupivacaine.

Why is "Ester linkage with rapid plasma hydrolysis" not the answer?

Ropivacaine is an amide, and ester hydrolysis in plasma is a feature of chloroprocaine.

What concept does this question test?

It tests CNS drugs and antiepileptics: ropivacaine versus bupivacaine in Pharmacology. It is less lipophilic, so it produces less motor block and has a lower risk of cardiac toxicity if absorbed or injected intravascularly. Its potency is a little lower than that of bupivacaine.

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 CNS drugs and antiepileptics: ropivacaine versus bupivacaine?

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.