A habitual sniffer of cocaine powder presents with recurrent epistaxis. Examination reveals a perforated nasal septum. Which pharmacological action of cocaine best explains this finding?

• A Inhibition of dopamine reuptake causing intense vasoconstriction
• B Direct caustic destruction of the cartilaginous septum by the drug
• C Stimulation of alpha-1 receptors leading to rebound vasodilation and tissue necrosis
• D Local anaesthetic action with blockade of voltage-gated sodium channels producing intense vasoconstriction of nasal vessels ✓

Explanation

Cocaine is both a local anaesthetic, blocking voltage-gated sodium channels, and a potent sympathomimetic causing marked vasoconstriction of nasal mucosal vessels through noradrenergic potentiation. Chronic ischaemia of the septal cartilage leads to ulceration and perforation. The drug itself is not caustic, which kills option B, and the perforation results from ischaemia rather than dopaminergic or rebound effects, ruling out A and C.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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