💊 Ivabradine

Ivabradine is a selective and specific inhibitor of the 'funny' current (If) in the sinoatrial node, leading to a reduction in heart rate.

It selectively inhibits the If current in the sinoatrial node, which is responsible for the spontaneous diastolic depolarisation of pacemaker cells. This slows the heart rate without affecting myocardial contractility, intracardiac conduction, or blood pressure significantly.

Ivabradine is indicated for the symptomatic treatment of chronic stable angina pectoris in adults with normal sinus rhythm who have a contraindication or intolerance to beta-blockers, or whose heart rate is above 70 beats per minute and remains uncontrolled by beta-blockers. It is also used in chronic heart failure with reduced ejection fraction (HFrEF) in patients in sinus rhythm with a heart rate ≥75 bpm, in combination with standard therapy.

Absolute contraindications include acute unstable angina, cardiogenic shock, severe hypotension, and sick sinus syndrome. It is also contraindicated in severe hepatic impairment, heart rate <70 bpm at rest before treatment, and in combination with strong cytochrome P450 3A4 inhibitors. Pregnancy and breastfeeding are also contraindications.

The most common adverse effect is luminous phenomena (phosphenes), a transient visual disturbance often described as flashes of light, due to its effect on retinal If channels. Bradycardia is also common and can be severe. Other effects include headache and dizziness. Atrial fibrillation can occur.

Heart rate should be measured before and during treatment to ensure it remains above the contraindication threshold and to monitor for bradycardia. Patients should be advised to report any visual disturbances. Efficacy in reducing angina symptoms or improving heart failure symptoms should be assessed.

Always check the patient's resting heart rate before prescribing and ensure it is within the appropriate range. Counsel patients about the potential for visual disturbances and to report them. Emphasise that it is not a first-line treatment for angina or heart failure, but rather an add-on or alternative.

Ivabradine specifically targets the If current, reducing heart rate without affecting contractility. The key adverse effect is luminous phenomena. It's used in stable angina (when beta-blockers are unsuitable/ineffective) and HFrEF (HR ≥75 bpm). Remember the contraindication with strong CYP3A4 inhibitors.

SBA questions often focus on its unique mechanism of action (If current inhibition) and its specific indication in patients intolerant to beta-blockers or with a high heart rate. The characteristic adverse effect of luminous phenomena is a common differentiator. Watch for scenarios involving bradycardia or atrial fibrillation.