Which property makes cocaine unique among the clinically used local anaesthetic agents?

• A It is the only agent effective by topical route
• B It is the only ester metabolised by liver microsomal enzymes
• C It is the only agent safe in patients with sulpha allergy
• D It is the only agent that produces vasoconstriction without an added vasoconstrictor ✓

Explanation

Cocaine blocks the reuptake of noradrenaline at sympathetic nerve endings, producing intense intrinsic vasoconstriction, so it is useful topically in ENT surgery where combined anaesthesia and vasoconstriction are wanted. All local anaesthetics work topically if placed on mucosa, amides rather than esters concern patients with PABA sensitivity, and cocaine, like all esters, is hydrolysed by plasma pseudocholinesterase, not by hepatic microsomes.

Reference: Morgan and Mikhail Clinical Anesthesiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.