Local Anaesthetic Mechanism — MFDS Part 1 MCQ

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EasyPharmacologyLocal Anaesthetic MechanismMFDS Part 1

What is the primary mechanism by which local anaesthetics prevent conduction of nerve impulses?

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Correct answer: D — Blockade of voltage-gated sodium channels in axonal membranes

Local anaesthetics primarily produce conduction block by inhibiting voltage-gated sodium channels in axonal membranes. Reduced sodium influx prevents the rapid depolarisation required to initiate and propagate an action potential. The uncharged drug fraction facilitates access across the lipid membrane, while protonated drug can interact with sites within the channel pore; channel state and alternative hydrophobic access pathways also influence blockade. Potassium-channel blockade is not the principal local anaesthetic mechanism. GABA-receptor activation is associated with several central sedative drugs, acetylcholinesterase inhibition increases cholinergic transmission, and opening presynaptic calcium channels would promote rather than suppress neurotransmitter release.

Reference: Körner J, et al. Sodium Channels and Local Anesthetics—Old Friends With New Perspectives. Frontiers in Pharmacology. 2022;13:837088. https://pubmed.ncbi.nlm.nih.gov/35418860/