Ivabradine reduces heart rate without affecting myocardial contractility or blood pressure. The molecular target responsible for this selective chronotropic effect is:

• A L-type calcium channel in the AV node selectively
• B Funny current (If) channel (HCN4) in the sinus node, reducing the rate of slow diastolic depolarization ✓
• C Hyperpolarization-activated cyclic nucleotide-gated channel HCN2 in the atrial myocardium
• D IKs (slow delayed rectifier potassium channel) in the sinus node

Explanation

Ivabradine selectively and specifically inhibits the hyperpolarization-activated cyclic nucleotide-gated channel HCN4 (responsible for the funny current, If) in sinoatrial node pacemaker cells. The If current is a mixed Na+/K+ inward current activated during diastolic depolarization (phase 4); its inhibition slows the rate of spontaneous depolarization, reducing heart rate. Because If channels are absent from contractile myocardium, ivabradine does not affect inotropy, dromotropy, or vasomotor tone. It is used for stable angina in patients intolerant of beta-blockers and for symptomatic heart failure with HR >70 bpm despite beta-blocker therapy.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.