Ivabradine is used for heart failure and stable angina in patients with contraindications to beta blockers. Its mechanism of action is best described as:
- A L-type calcium channel blockade reducing SA node automaticity
- B Non-selective beta-1 and beta-2 adrenergic blockade in the SA node
- C Selective blockade of the I(f) (funny current) HCN channel in the SA node, reducing heart rate without affecting contractility ✓
- D Activation of adenosine A1 receptors in the AV node, prolonging PR interval
Explanation
Ivabradine specifically blocks the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that carry the I(f) current — the 'funny current' that drives spontaneous diastolic depolarization in SA node pacemaker cells. By reducing I(f), it slows the rate of spontaneous depolarization, decreasing heart rate (pure negative chronotropy) without affecting contractility (no negative inotropy), automaticity outside the SA node, or intracardiac conduction. This makes it distinct from beta blockers and calcium channel blockers. It is contraindicated in atrial fibrillation as it has no effect on AV node conduction.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.