Ivabradine reduces heart rate in stable angina by:
- A Blocking L-type calcium channels in sinoatrial and AV node
- B Stimulating cardiac muscarinic M2 receptors
- C Selectively inhibiting the funny (If) current in sinoatrial node pacemaker cells ✓
- D Non-selective β-adrenergic receptor blockade
Correct answer: C. Selectively inhibiting the funny (If) current in sinoatrial node pacemaker cells
Explanation
Ivabradine specifically blocks the HCN channel responsible for the hyperpolarisation-activated mixed cation current (If) in sinoatrial pacemaker cells. This current drives spontaneous depolarisation; its inhibition slows the rate of phase 4 depolarisation without affecting contractility, conduction, or blood pressure. Unlike verapamil (L-type Ca2+ blocker), ivabradine has no negative inotropic effect.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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