Question

The topical use of which of the following local anaesthetics is not recommended?

• A. Lignocaine
• B. Bupivacaine
• C. Cocaine
• D. Dibucaine

Hint:

Bupivacaine penetrates mucosa poorly and is unusually cardiotoxic if absorbed, so surface or topical use is avoided even though lignocaine, cocaine, and dibucaine are all used topically.

Answer 1

The Correct Option is B

Step 1: Group the drugs by their family first.
All four are local anaesthetics that numb tissue by blocking sodium channels along a nerve. The question is really asking which one is unsafe or unreliable when placed directly on a mucous surface rather than injected.

Step 2: Confirm the three that are used topically.
Lignocaine is one of the most common topical anaesthetics, used before procedures on the throat or skin. Cocaine, despite its abuse potential, still has a place in nasal and eye procedures because it numbs and constricts blood vessels at the same time. Dibucaine also penetrates skin and mucosa well enough for topical creams.

Step 3: Ask what goes wrong with bupivacaine specifically.
Bupivacaine does not cross mucous membranes efficiently, so a topical dose gives patchy, unreliable numbness. If enough of it does get absorbed, it binds strongly to heart sodium channels and is slow to let go, and this combination can set off dangerous heart rhythm problems that are hard to treat.

Step 4: Conclude.
The poor mucosal penetration plus the high cardiotoxic potential is why bupivacaine is kept away from topical or surface application.
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