Which Vaughan-Williams class of antiarrhythmic drugs works by BLOCKING cardiac sodium channels and is the class used by lignocaine?
- A Class II
- B Class I ✓
- C Class III
- D Class IV
Correct answer: B. Class I
Explanation
Class I antiarrhythmics block fast sodium channels, reducing the rate of depolarisation (Phase 0 of action potential) and slowing conduction velocity. They are subclassified: Ia (quinidine, procainamide) prolong APD; Ib (lignocaine, mexiletine) shorten APD; Ic (flecainide, propafenone) have no effect on APD. Class II are beta-blockers, Class III block potassium channels, and Class IV are calcium channel blockers.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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