Ivabradine protects against episodes of angina by reducing the myocardial oxygen demand through slowing of the heart rate.

Heart rate is determined by electrical pacemaker activity in the sinoatrial node (SAN) controlled by the I_f channels. Ivabradine blocks the I_f channels reducing the firing rate of the pacemaker cells. This inhibition of the I_f current substantially lowers the heart rate.⁸

At recommended doses ivabradine reduces the heart rate by approximately 10bpm which reduces cardiac workload and myocardial oxygen consumption.⁹

Ivabradine has no effect on blood pressure or the force of cardiac contraction.

An additional benefit of a reduction in the heart rate is increasing the duration of diastole leading to better perfusion of the myocardium.

Ivabradine is licensed for the treatment of stable angina in adults with a normal sinus rhythm and heart rate (above 70bpm) who are unable to tolerate beta blockers or where beta blockers are contra-indicated.

It can also be used in combination with beta blockers where heart rate is not adequately controlled by beta blockers alone.

Ivabradine should not be administered with drugs that prolong the QT interval as this effect may be exacerbated with a risk of arrhythmia.

Ivabradine should not be used with the rate controlling calcium channel blockers, diltiazem or verapamil, due to the increased risk of bradycardia. Bradycardia is clinically defined as a resting heart rate of less than 60bpm in adults.

Side effects

A very common side effect of ivabradine that affects more than 10% of patients are phosphenes or luminous phenomena. These are brief moments of increased visual brightness which occur because there are I_h channels within the retina that are similar in structure to the I_f channels within the sinoatrial node. Patients who are prescribed ivabradine should be warned about the possibility of this side effect.

Other common side effects include headache (especially during the first month of treatment), blurred vision, dizziness and bradycardia. Ivabradine has been associated with an increased risk of atrial fibrillation. Patients should be monitored regularly for cardiac rhythm disturbance.

Patients are usually initiated at a dose of 5mg twice a day; increasing if necessary after three or four weeks to 7.5mg twice daily provided the heart rate remains above 60bpm. In elderly patients, or where the 5mg dose is not tolerated, the dose can be reduced to 2.5mg twice daily.

Where ivabradine does not improve symptomatic control after 3 months treatment should be discontinued.

⁸ Sulfi S, Timmis AD. Ivabradine- the first selective sinus node I_f channel inhibitor in the treatment of stable angina. Int. J. Clin. Pract. February 2006; 60(2): 222-228.
⁹ Summary Product Characteristics: Procoralan. Electronic Medicines Compendium (eMC). https://www.medicines.org.uk/emc/medicine/17188. Updated June 7, 2016.