HCN Channel Blockers

Reviewed by: HU Medical Review Board

HCN channel blockers are drugs used to treat certain people with heart failure (HF). HCN stands for “hyperpolarization-activated cyclic nucleotide-gated.” HCN channels conduct an electrical current that regulates the pace of the heartbeat. Blocking HCN channels slows your heartbeat. This can improve health outcomes for people with HF.1,2

Corlanor® (ivabradine) is the only HCN channel blocker approved by the US Food and Drug Administration (FDA) for HF. It can reduce the risk of hospitalization for certain people with HF. Serious side effects are possible. Talk to your doctor about the risks and benefits of HCN channel blockers.3

How do HCN channel blockers work?

Many people with chronic HF have a high resting heart rate. A high resting heart rate is linked to worse outcomes. The heart may also not contract well. This reduces how much oxygen-rich blood it pumps out to the rest of the body.1,4

HCN channel blockers work by reducing your resting heart rate. This can help the heart pump more blood with each beat. Reducing your heart rate lowers the risk of HF getting worse.1,2

HCN channels are present on the surface of heart muscle cells. They conduct an electrical current called the “pacemaker current.” This current is an important part of the system that sets the heart rhythm. Blocking the current slows heart rate.1

HCN channel blockers work best for people with high resting heart rates. This means they reduce heart rate more in people with a higher baseline heart rate. HCN channel blockers have less of an effect when your resting heart rate is already low.1


There is only 1 FDA-approved HCN channel blocker for HF: Corlanor (ivabradine). Corlanor lowers the risk of hospitalization and death from worsening HF.3,5

Corlanor can be used to treat adults who meet all of the following conditions:3,5

  • Have stable, symptomatic chronic HF
  • Have reduced “left ventricular ejection fraction” (not enough blood pumping out of the heart)
  • Have a resting heart rate over 70 beats per minute
  • Are taking the maximum dose of beta-blockers or cannot take beta-blockers

Corlanor can also be used to treat children over 6 years old who have all of these:3,5,6

  • Stable, symptomatic chronic HF
  • Dilated cardiomyopathy (which causes the ventricles to enlarge and makes it harder for your heart to pump blood effectively)
  • A high heart rate

What are possible side effects?

Side effects vary depending on the specific drug you are taking. The most common side effects of HCN blockers include:3,5

  • Increased blood pressure (hypertension)
  • Temporary brightness in part of your field of vision

HCN channel blockers increase the risk of irregular or rapid, quivering heartbeat. This is called atrial fibrillation. Tell your doctor if you notice symptoms of atrial fibrillation, such as:3,5

  • Pounding or racing heartbeat
  • Chest pressure
  • Worsened shortness of breath
  • Dizziness or fainting

HCN channel blockers can cause a slower than normal heart rate. This is called bradycardia. Tell your doctor if you notice symptoms of bradycardia, such as:3,5

  • Fatigue
  • Lack of energy
  • Dizziness

These are not all the possible side effects of HCN channel blockers. Talk to your doctor about what to expect when taking HCN channel blockers. You also should call your doctor if you have any changes that concern you when taking HCN channel blockers.

Other things to know

Take HCN channel blockers as your doctor describes. Corlanor is taken by mouth and with food. Your doctor may change your dose to achieve the right resting heart rate.2,3,5

Do not eat grapefruit or drink grapefruit juice while taking HCN channel blockers. HCN channel blockers can cause harm to unborn babies. Use birth control during treatment. Tell your doctor if you become pregnant during treatment.5

Certain other medicines and health conditions make HCN channel blockers unsafe. Before beginning treatment for HF, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.5

For more information, read the full prescribing information of Corlanor.

By providing your email address, you are agreeing to our privacy policy.