Ivabradine is used in stable angina and HFrEF with heart rate >70 bpm. Its unique mechanism is best described as:
- A Selective inhibition of the hyperpolarisation-activated funny current (If) in the sinoatrial node pacemaker cells ✓
- B Blockade of L-type calcium channels in the sinoatrial node
- C Beta-1 adrenoceptor partial agonism, reducing chronotropy without full blockade
- D Blockade of IKs (slow delayed rectifier potassium channel) to prolong phase 4 depolarisation
Correct answer: A. Selective inhibition of the hyperpolarisation-activated funny current (If) in the sinoatrial node pacemaker cells
Explanation
Ivabradine selectively and specifically inhibits the HCN (hyperpolarisation-activated cyclic nucleotide-gated) channels in the sinoatrial node that carry the 'funny current' (If). If is a mixed Na+/K+ inward current that governs diastolic depolarisation (phase 4) in pacemaker cells, determining heart rate. By blocking If, ivabradine slows the rate of phase 4 depolarisation exclusively in the SA node, reducing heart rate without affecting contractility, conduction, or blood pressure. It has no effect on beta receptors, L-type channels, or IKs.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.