What are the indications, dosing, and side effects of ivabradine (heart rate reducer)?

Ivabradine: Mechanism, Indications, Dosing, and Side Effects

Mechanism of Action

Ivabradine is a selective inhibitor of the If (funny) current in the sinoatrial node that reduces heart rate without affecting blood pressure, myocardial contractility, or ventricular conduction. 1 This unique mechanism distinguishes it from beta-blockers by providing pure heart rate reduction without negative inotropic effects. 2

Primary Indication

Ivabradine is FDA-approved to reduce the risk of hospitalization for worsening heart failure in adult patients with stable, symptomatic chronic heart failure with left ventricular ejection fraction ≤35%, who are in sinus rhythm with resting heart rate ≥70 beats per minute and either are on maximally tolerated doses of beta-blockers or have a contraindication to beta-blocker use. 3

Key Patient Selection Criteria:

• Must be in sinus rhythm (not for atrial fibrillation or 100% atrial pacing) 1
• Heart rate persistently ≥70 bpm despite optimal beta-blocker therapy 1
• NYHA functional class II-IV symptoms 1
• History of heart failure hospitalization within the previous year strengthens the indication 1
• A history of paroxysmal atrial fibrillation is NOT a contraindication 1

Dosing Recommendations

Starting Doses:

• Standard dose: 5 mg twice daily with meals 1, 3
• Reduced dose: 2.5 mg twice daily for patients with history of conduction defects or age ≥75 years 1, 3

Titration:

• Assess heart rate after 2 weeks of treatment 3
• Maximum dose: 7.5 mg twice daily 1, 3
• Adjust based on heart rate response and tolerability 1

Critical Dosing Context:

Before initiating ivabradine, beta-blocker therapy should be optimized to the maximum tolerated or target dose. 1 Ivabradine is an adjunctive therapy, not a beta-blocker replacement. 1

Clinical Efficacy

The SHIFT trial demonstrated that ivabradine added to guideline-directed medical therapy resulted in: 1

• 18% relative risk reduction in cardiovascular death or heart failure hospitalization (p<0.0001) 1
• 26% relative risk reduction in heart failure hospitalizations 1
• 74% relative risk reduction in deaths due to heart failure 1
• Number needed to treat: 24 patients for 23 months to prevent one event 1
• Improved left ventricular function and quality of life 1

Benefits were particularly pronounced in patients with heart rate ≥77 bpm at baseline. 1

Side Effects

Common Adverse Reactions (≥1% incidence):

Bradycardia:

• Occurs in 10% of patients on ivabradine vs 2.2% on placebo 3
• 5% experience symptomatic bradycardia vs 1% on placebo 1
• Monitor heart rate regularly, especially when combining with other negative chronotropes 1, 3

Phosphenes (Visual Brightness Phenomena):

• Reported by 2.8-3% of patients on ivabradine vs 0.5-1% on placebo 1, 3
• Described as transiently enhanced brightness in limited visual field areas, halos, image decomposition, colored bright lights, or multiple images 3
• Usually triggered by sudden variations in light intensity 3
• Generally mild to moderate intensity and onset within first 2 months 3
• Led to treatment discontinuation in <1% of patients 3
• Most resolve during or after treatment 3

Atrial Fibrillation:

• Occurs in 8.3% of patients vs 6.6% on placebo 3
• Monitor patients for new-onset atrial fibrillation 3

Hypertension/Blood Pressure Increase:

• Reported in 8.9% of patients vs 7.8% on placebo 3

Postmarketing Adverse Reactions:

Syncope, hypotension, torsade de pointes, ventricular fibrillation, ventricular tachycardia, angioedema, erythema, rash, pruritus, urticaria, vertigo, diplopia, and visual impairment have been reported. 3

Absolute Contraindications

Ivabradine is contraindicated in: 3

• Acute decompensated heart failure
• Clinically significant hypotension (blood pressure <90/50 mm Hg)
• Sick sinus syndrome, sinoatrial block, or 3rd-degree AV block (unless functioning demand pacemaker present)
• Clinically significant bradycardia
• Severe hepatic impairment
• Heart rate maintained exclusively by pacemaker
• Concomitant use with strong CYP3A4 inhibitors (boceprevir, clarithromycin, indinavir, itraconazole, ketoconazole, lopinavir/ritonavir, nelfinavir, ritonavir, saquinavir, telaprevir, posaconazole, voriconazole)

Important Precautions

Drug Interactions:

• Avoid strong CYP3A4 inhibitors and inducers (including grapefruit juice, St. John's wort, carbamazepine, phenytoin, rifampin) 1, 3
• Avoid diltiazem and verapamil due to additive heart rate-lowering effects 1
• Use caution with other negative chronotropes (digoxin, amiodarone) and monitor heart rate closely 3

Special Populations:

• Not recommended in 2nd-degree AV block 1
• Pregnancy: Fetal toxicity risk—females should use effective contraception 3
• Lactation: Breastfeeding not recommended 3

Off-Label Use: Inappropriate Sinus Tachycardia (IST)

Ivabradine at 2.5-7.5 mg twice daily significantly reduces heart rate and improves symptoms in patients with IST. 1, 4 The ACC/AHA/HRS guidelines give this a Class IIa recommendation. 1 In one observational study, ivabradine was more effective than metoprolol for heart rate reduction and symptom improvement in IST. 1, 4

Clinical Pearls

• Ivabradine provides heart rate reduction without the hypotension, bronchospasm, or negative inotropy associated with beta-blockers 1, 2
• The drug is particularly valuable in patients who cannot tolerate beta-blocker up-titration due to hypotension or fatigue 1, 4
• Take with meals to optimize absorption 3
• Visual side effects (phosphenes), while noticeable, rarely lead to discontinuation and typically resolve 3
• The BEAUTIFUL trial confirmed excellent safety in patients with coronary artery disease, though it did not reduce the primary composite endpoint in that population 1, 5