Lignocaine (lidocaine) is used as a local anaesthetic. The mechanism by which it blocks nerve conduction is:

• A It closes potassium channels, hyperpolarising the axonal membrane
• B It antagonises calcium channels on Schwann cells, reducing myelin conduction
• C It binds the intracellular face of voltage-gated Na+ channels in the open/inactivated state, blocking Na+ influx in a use-dependent manner ✓
• D It activates inhibitory GABA-B receptors on peripheral sensory neurons

Explanation

Local anaesthetics are tertiary amines that penetrate the nerve membrane in the uncharged (free base) form, become protonated intracellularly, and then bind to a receptor site within the inner vestibule of the voltage-gated Na+ channel. They preferentially bind open and inactivated channel states (use-dependence/frequency-dependence), blocking Na+ influx and preventing action potential propagation. Small, unmyelinated C-fibres (pain) are blocked before large myelinated motor fibres.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.