Calcium Channel Blockers: What Are They and How Do They Work?
Key takeaways:
Calcium channel blockers (CCBs) are medications used to treat high blood pressure and other heart-related health conditions. They work by relaxing the blood vessels in the body.
Although there were some concerns about the safety of CCBs, studies have shown them to be safe and effective. They’re considered a first-choice medication class to treat high blood pressure.
CCBs may interact with other medications. So be sure to check with your pharmacist or healthcare provider before starting any new medication while taking CCBs. If you experience side effects from CCBs, be sure to let your provider know.
Do you have high blood pressure, chest pain, or migraines? If so, you might already be familiar with a class of medication called calcium channel blockers (CCBs). But there may be some things about them — like how they work — that you might not know about.
What are calcium channel blockers?
If you have high blood pressure, CCBs might be one of the first types of medication your healthcare provider prescribes. But that’s not all they can treat. Some CCBs can also help with conditions like coronary artery disease, angina (chest pain), and arrhythmias (irregular heart beats). They’re also used off-label for pulmonary hypertension and migraine prevention.
Some common CCBs are:
Amlodipine (Norvasc, Katerzia)
Nifedipine (Procardia, Procardia XL)
Nisoldipine (Sular)
And there are a few other CCBs that work differently from the rest:
Diltiazem (Cardizem)
Diltiazem ER (Cardizem CD, Cardizem LA, Cartia XT)
Verapamil ER (Calan SR, Verelan)
You may have heard that some blood pressure medications work better for people of certain racial backgrounds. CCBs, however, seem to be equally effective across all racial groups.
Read more like this
Explore these related articles, suggested for readers like you.
How do calcium channel blockers work?
CCBs work by relaxing blood vessels in the body. But their exact mechanism of action is a bit more complex.
Calcium enters the muscles of your heart and blood vessels through tiny pores called calcium channels. Calcium helps your heart and arteries contract to deliver blood and oxygen to your body. But for many people with heart disease and high blood pressure, those muscles are working too hard.
Blocking the calcium channels keeps calcium from coming in. Ultimately, this relaxes the arteries so that more oxygen can get to the heart. It also lowers blood pressure and makes it easier for the heart to pump blood. This is generally how all CCBs work, but there are some differences, too.
Dihydropyridine vs. non-dihydropyridine CCBs
There are two main types of CCBs: dihydropyridine and non-dihydropyridine.
Most CCBs are known as dihydropyridine CCBs. These are the ones that end in ”ipine,” as in amlodipine. They don’t affect the strength or rate of the heart’s contractions.
But diltiazem and verapamil are known as non-dihydropyridine CCBs. They have more significant effects on the heart than the dihydropyridine CCBs. Specifically, they lower the strength and speed of heartbeats. This makes them especially useful for people who have an irregular heartbeat or other heart-related problems.
How long do calcium channel blockers take to work?
Some CCBs start working within 1 to 4 hours of taking the first dose, but it often takes up to 2 to 4 weeks for the full effects to kick in. This can vary depending on the CCB. Your healthcare provider can give you more information about the specific CCB you’re taking.
Food affects individual CCBs differently. For example, taking felodipine and eating a high-fat meal can result in higher levels of the medication in the body. But taking nicardipine and eating the same meal can result in lower levels of the medication in the body. Ask your healthcare provider whether you should take your CCB with or without food.
Are calcium channel blockers safe?
In the early 1990s, a CCB called lidoflazine was found to increase the risk of irregular heartbeat and death. Due to this, it was never brought to market, and concern grew that other CCBs might also be unsafe. Then, a study published in 1995 claimed that short-acting nifedipine could increase the risk of death in people with heart disease. This led to even more concern over the safety of CCBs.
However, a very large study, called the ALLHAT trial, came to a different conclusion. This study was sponsored by the National Heart, Lung, and Blood Institute and followed over 30,000 people with high blood pressure. It compared the CCB amlodipine with two other standard hypertension treatments: lisinopril and chlorthalidone. The study concluded that there was no increased risk of death with CCB treatment compared to the other medications.
A second study, the ACTION trial, compared long-acting nifedipine to a placebo (a pill with no medication in it) and came to the same conclusion.
These studies helped calm concern about CCB safety, and they are now used as a first-choice medication class for high blood pressure and other heart-related conditions.
Common side effects
The most common side effects of dihydropyridine CCBs are:
Flushing
Headaches
Edema (swelling in the extremities, especially the legs and feet)
Dizziness
The side effects of non-dihydropyridine CCBs include constipation and a low heart rate.
As your body gets used to taking a CCB, side effects like flushing and headaches usually go away. But if these side effects linger or become bothersome, be sure to let your healthcare provider know.
Severe side effects
Severe CCB side effects are rare, but include changes in heart rhythm and blood pressure. Remember that verapamil and diltiazem, in particular, keep the heart from pumping as hard and fast as usual. For that reason, your healthcare provider may not prescribe these medications if you have heart failure or another condition that lowers your heart function.
If you experience shortness of breath or sudden chest pain while taking a CCB, seek emergency medical care. These could be signs your heart isn’t working the way it should.
Will calcium channel blockers interact with my other medications?
Certain medications are known to interact with CCBs. These include:
Azole antifungals, like itraconazole (Sporanox)
Beta-blockers, like atenolol (Tenormin)
Digoxin (Lanoxin)
Some chemotherapy medications
Before you take a CCB, ask your healthcare provider or pharmacist to review your entire medication list to be sure there are no serious drug interactions. If there are, your doctor may change your dose of either medication or may prescribe a new medication altogether.
You may need to avoid drinking grapefruit juice while taking some CCBs, since it may raise levels of the medication in your blood. This could be dangerous, causing your blood pressure to drop too low.
The bottom line
Calcium channel blockers (CCBs) are medications used for high blood pressure and other heart-related conditions. They work by relaxing the blood vessels in the body.
Although there were some early concerns about the safety of CCBs, newer studies have shown them to be safe and effective. They’re considered a first-choice medication class for high blood pressure.
CCBs may interact with some medications. So be sure to check with your pharmacist or healthcare provider before starting any new medication if you’re taking a CCB. If you experience side effects from CCBs, be sure to let your provider know.
Why trust our experts?
References
ANI Pharmaceuticals, Inc. (2021). Nicardipine hydrochloride [package insert].
Bansal, A. B., et al. (2022). Felodipine. StatPearls.
Elliott, W. J., et al. (2011). Calcium channel blockers. The Journal of Clinical Hypertension.
Godfraind, T. (2017). Discovery and development of calcium channel blockers. Frontiers in Pharmacology.
National Hearth, Lung, and Blood Institute. (n.d.). Antihypertensive lipid-lowering treatment to prevent heart attack trial (ALLHAT).
Nguyen, T. T., et al. (2009). Racial differences in blood pressure response to calcium channel blocker monotherapy: A meta-analysis. American Journal of Hypertension.
Poole-Wilson, P. A., et al. (2006). Safety of nifedipine GITS in stable angina: The ACTION trial. Cardiovascular Drugs and Therapy.
