• Heart Disease

Verapamil Uses, Side Effects, and Drug Interactions

Medically reviewed and edited by Cara Konzel, MS, RN, ACNP-BC

Verapamil is a versatile drug that can treat several medical conditions and it has been widely used for decades. Currently, over three million verapamil prescriptions are issued each year.

This prescription medication is sold under various brand names and may be administered orally or via intravenous injection.

Individuals who have been prescribed verapamil may experience certain side effects. Some of these are fairly common and typically subside once the body adjusts to the medication.

However, this medication can cause more serious side effects that require medical attention.

In this article, we will discuss what verapamil is used for, its common side effects, and how to take this medication safely.

What is Verapamil?

Verapamil is a calcium channel blocker. Calcium channels are proteins found in the cell membranes of the heart and blood vessels.

This calcium channel blocker is typically available as an immediate-release or extended-release tablet, with the choice of formulation depending on the disease being treated.

Usually, doctors who prescribe verapamil will require regular follow-ups with patients to monitor their blood pressure, heart rate, and liver function.

How Does Verapamil Work?

The calcium present in the body controls the heart rhythm and how the blood vessels contract or relax.

Verapamil impacts the movement of calcium into the cells of the heart and blood vessels.

In doing so, it relaxes the blood vessels and increases the supply of oxygen to the heart, reducing its workload.

It also slows down the electrical activity in the heart, which can help regulate and control heart rate.

What is Verapamil Used For?

Verapamil is mostly prescribed to treat hypertension (high blood pressure) as it dilates the blood vessels, thereby easing the demand on the heart.

This medication also effectively prevents chest pain (angina) that is caused by the heart not receiving enough oxygenated blood due to restricted arteries.

In addition, it may be used to treat a fast or irregular heartbeat (arrhythmia) as it can help to control and manage heart rhythms.

In some cases, verapamil is also effective in treating migraines and cluster headaches.

Common Side Effects of Verapamil

As with many other medications, verapamil can cause side effects. The most common side effects that people report are:

Constipation

As verapamil’s primary function is to smooth muscle cells, it can slow down the natural contractions in the digestive tract.

When the muscles in the digestive tract are less active, food and waste may move through the body at a slower rate.

The longer stool remains in the colon, the harder and more dry it becomes, making it difficult to pass.

This slowed movement and hardness may result in constipation for some individuals taking verapamil.

Dizziness

The main reason why people who take verapamil experience dizziness or lightheadedness is due to its impact on blood pressure and heart rate.

As verapamil works to lower blood pressure, it can result in reduced oxygen delivery to the brain, which may cause this adverse effect.

If blood pressure is already lowered by verapamil, you may also feel dizzy when moving from a seated to a standing position, as this changes the blood pressure in the body.

Dizziness poses a risk as it can cause fainting spells or falls, especially in individuals who are not stable on their feet. We’ll explain how this can be prevented later in this article.

Headaches

It’s not completely understood why verapamil causes headaches, but it might be a result of how the drug impacts blood flow in the brain.

While verapamil’s ability to widen blood vessels can help treat high blood pressure, dilated blood vessels in the brain can change blood flow and may cause headaches.

Some people are naturally more sensitive to new medications than others. This sensitivity may trigger headaches when starting the medication before the body adjusts.

Flushing

Flushing is characterized by sudden and temporary redness of the skin. It’s often accompanied by a warm sensation.

Dilated blood vessels can increase blood flow to the skin, allowing for more circulation, which may result in some flushing.

Swelling

If you take verapamil, you may experience swelling in your extremities (peripheral edema), including your hands, feet, ankles, and legs.

This is because of the drug’s impact on blood vessels. When blood vessels in the extremities expand, it can cause a fluid buildup in the surrounding tissues, resulting in swelling.

Fatigue

Although the association between fatigue and verapamil is not entirely understood, there are three potential causes of this side effect:

• Regulation of blood pressure: This medication can result in the reduction of blood flow throughout the body, including in the brain, which may cause feelings of fatigue.

• Reduced cardiac workload: Although verapamil is designed to reduce the heart’s workload, this mechanism may result in tiredness.

• Heart rate changes: Verapamil can slow the heart rate because it impacts the electrical signals that generate heart rhythm. While this is beneficial for people with arrhythmias, it may lead to fatigue.

Nausea

While somewhat more rare than the other side effects listed above, some people taking verapamil may experience nausea.

This may be because verapamil impacts the gastrointestinal system, which can change the functioning of the gut, potentially leading to nausea.

The slowed movement of food and waste through the body mentioned earlier can also cause feelings of fullness, discomfort, and nausea.

Low blood pressure

As verapamil works to slow down the heart’s workload and lower blood pressure, it may result in abnormally low blood pressure, known as hypotension.

Serious Side Effects of Verapamil

Verapamil may cause more serious side effects in some individuals. If you experience any of the adverse effects listed below, it’s important to call your doctor and seek medical attention.

Heart rhythm disturbances

While verapamil is intended to treat certain heart rhythm disorders, it can also make other rhythm issues worse. These include a very slow heart rate (bradycardia) and impaired electrical signals in the heart (heart block).

An allergic reaction

Although rare, some people may have an allergic reaction to verapamil. Symptoms of a serious allergic reaction include hives on the skin, itching, a rash, swelling, difficulty breathing, and severe dizziness.

Liver problems

There’s the potential, in rare cases, that people taking verapamil may have elevated liver enzyme levels. This can progress into liver injury or disease.

Gastrointestinal issues

When left untreated, severe constipation can lead to more serious gastrointestinal problems such as bowel obstruction.

Central nervous system effects

While uncommon, verapamil may cause side effects such as confusion, hallucinations, and mood changes.

Respiratory distress

Verapamil may worsen pre existing respiratory conditions. It may also cause breathing difficulties and shortness of breath.

What to Tell Your Doctor Before Taking Verapamil

If your doctor prescribes verapamil, they will likely get a full medical history from you before you start taking the medication.

However, it’s important to let your doctor know if you’ve ever suffered from:

• Kidney or liver disease

• Sick sinus syndrome (SSS)

• Congestive heart failure

Your health care provider will also need to know if you are taking any other medications, including vitamin or herbal supplements.

Verapamil Brand Names

This medication is typically sold under the following brand names:

• Calan

• Calan SR

• Covera-HS

• Isoptin SR

• Verelan

• Verelan PM

How to Take Verapamil

Depending on the formulation of verapamil you’ve been prescribed, you may need to take this oral medication several times a day:

• Immediate-release formulations: These are taken three or more times a day

• Extended-release formulations: These are usually taken once or twice a day

You should take your verapamil at the same time each day. Your doctor will typically tell you when it’s best for you to take your medication.

Be sure to closely follow the instructions on the prescription label to avoid unpleasant side effects.

Here is some other important information to keep in mind when taking verapamil:

Missing a dose

If you forget to take your verapamil, you can take the missed dose as soon as you remember.

But if it’s almost time for your next dose, skip it and continue with your regular dosing schedule.

Lower your risk of dizziness

As mentioned above, side effects of verapamil may include dizziness and lightheadedness.

To prevent fainting and falling, always rise slowly from a sitting or lying position. If you feel faint, ensure that you lie down until you feel better.

Continue to take your medication

Continue to take your verapamil even if you feel well and don’t have any symptoms of your medical condition. Don’t stop taking verapamil without talking to your doctor first.

What to Do If You Overdose on Verapamil

If you think you’ve taken too much verapamil, you must contact a poison control center and visit an emergency room immediately.

Symptoms of a verapamil overdose include:

• Swallowing or breathing difficulties

• Confusion

• Seizures

• Irregular heartbeat

• Blurred vision

• Severe dizziness

Verapamil Drug Interactions

Verapamil may interact with other medications and substances. Interactions mean the medication might not work as it should or it may have harmful side effects when used with these other substances.

Some interactions to be aware of include:

• High cholesterol medications such as simvastatin and lovastatin

• Beta blockers

• Other high blood pressure medication

• Digoxin

• Flecainide

• Lithium

• Carbamazepine

• Rifampin

• Phenobarbital

• Cyclosporine

• Vardenafil

Where Can I Learn More About Verapamil?

Through LifeMD, you can speak to a physician or nurse practitioner online via our telehealth platform.

A licensed healthcare provider can answer any questions you have about verapamil and prescribe this medication if necessary.

Visit our website to book your online consultation and skip the waiting room.

Cara Konzel, MS, RN, ACNP-BC

Cara earned her BA in Biology, BS in Nursing, and MS in Nursing — all from the University of Rochester. Cara's approach to medicine and patient care is grounded in years of experience and extensive knowledge. She combines compassion and personalized attention to ensure her patients feel valued, understood, and empowered to participate in their own health journey. Cara enjoys spending time with her three children, caring for her aging parents, and gardening.

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