Ivabradine is used for rate control in chronic stable angina and heart failure. Its mechanism of action is:
- A Selective blockade of β1 adrenoceptors in the SA node
- B Blockade of L-type voltage-gated calcium channels in the SA and AV nodes
- C Inhibition of the hyperpolarisation-activated cyclic nucleotide-gated (HCN) If 'funny' current in the SA node ✓
- D Enhancement of cardiac muscarinic M2 receptor signalling
Correct answer: C. Inhibition of the hyperpolarisation-activated cyclic nucleotide-gated (HCN) If 'funny' current in the SA node
Explanation
Ivabradine selectively and dose-dependently inhibits the If (funny) pacemaker current in sinoatrial node cells by blocking HCN channels, slowing the rate of diastolic depolarisation and thereby reducing heart rate without affecting conduction velocity, myocardial contractility, or blood pressure. This is distinct from β-blockers (β1 blockade), calcium channel blockers (L-type Ca2+ channel blockade), and cholinomimetics. Its lack of negative inotropy is advantageous in heart failure with reduced EF.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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