Key takeaways

  • Camzyos carries a boxed warning due to the risk of heart failure, requiring close monitoring by your doctor and regular echocardiograms.
  • Dizziness is a common side effect of Camzyos, and its risk may increase with grapefruit juice consumption and certain other medications.
  • Although not reported in studies, Camzyos may cause allergic reactions, ranging from mild to severe. Severe symptoms, such as swelling of your mouth, tongue, or throat, or difficulty breathing, require immediate medical attention.

Camzyos (mavacamten) is a prescription drug used to treat a heart condition called obstructive hypertrophic cardiomyopathy (HCM). Camzyos can cause side effects that range from mild to serious. Examples include dizziness and heart failure.

Specifically, Camzyos is used in adults to treat obstructive HCM that’s causing symptoms with physical activity.

Keep reading to learn about the more common, mild, and serious side effects Camzyos can cause. To learn more about Camzyos, including its use, dosage, and cost, see this Camzyos overview article.

Boxed warning: Risk of heart failure

This drug has a boxed warning for the risk of heart failure. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Tips for managing side effects” section.

Camzyos can cause certain side effects, some more common than others. These side effects may be temporary, lasting a few days to weeks. Talk with your doctor if side effects do not go away, get worse, or become too difficult to tolerate.

More commonly reported Camzyos side effects include:

Mild side effects have been reported with Camzyos. These include:

In most cases, these side effects should be temporary, and some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. Do not stop taking Camzyos unless your doctor recommends it.

Camzyos may cause mild side effects other than those listed here. See the drug’s prescribing information for details.

Camzyos may cause serious side effects. The following list may not include all possible serious side effects of the drug. For more information, you can refer to the prescribing information for Camzyos.

Serious side effects that have been reported include:

If you develop serious side effects while taking Camzyos, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect while taking Camzyos and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Allergic reaction

For some people, Camzyos can cause an allergic reaction. But this side effect wasn’t reported in the drug’s studies.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking Camzyos.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Camzyos, they may have you switch to a different treatment.

Learn more about some of the side effects Camzyos may cause.

Risk of heart failure

Camzyos has a boxed warning for the risk of heart failure. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Camzyos relaxes your heart muscle and can cause reduced ejection fraction. (Ejection fraction is a measure of how much blood your heart pumps out with each heartbeat.) Reduced ejection fraction was a rare side effect reported in studies of Camzyos, but it can lead to heart failure.

With heart failure, your heart can’t pump blood around your body effectively. Heart failure may cause symptoms such as:

Factors that can increase the risk of heart failure when taking this drug include:

What might help

Due to the risk of heart failure, Camzyos is only available through a risk evaluation and mitigation strategy (REMS) program. The FDA requires REMS programs for certain medications to help make sure they’re used safely.

Your doctor must be certified by the REMS program in order to prescribe Camzyos. And you’ll only be able to get the medication from a REMS-certified specialty pharmacy.

As part of the the REMS program, you’ll need to have echocardiograms before starting Camzyos and regularly throughout your treatment. This is so your doctor can monitor your heart function and make sure Camzyos remains safe for you.

To help prevent heart failure, do not drink grapefruit juice while taking Camzyos. And be sure to check with your doctor or pharmacist before taking any other drugs with Camzyos. This includes over-the-counter medications, herbal remedies, and supplements.

If you develop new or worsening symptoms of heart failure during Camzyos treatment, contact your doctor right away. They’ll likely recommend stopping Camzyos and switching to a different treatment for your condition.

Dizziness

Dizziness was a common side effect reported in studies of Camzyos. With dizziness, you may also feel lightheaded or nauseous. Sometimes, dizziness may lead to fainting.

Note that dizziness and fainting are also symptoms of obstructive hypertrophic cardiomyopathy, which Camzyos is used to treat. They can also be symptoms of heart failure, which is a possible serious side effect of Camzyos.

Factors that can increase the risk of dizziness when taking this drug include:

  • drinking grapefruit juice or alcohol
  • taking medications that interact with Camzyos, especially:
    • disopyramide (Norpace)
    • ranolazine (Aspruzyo Sprinkle)
    • verapamil (Verelan) with a beta-blocker
    • diltiazem (Cardizem CD, Cartia XT) with a beta-blocker
    • certain antifungals, such as itraconazole (Sporanox)
    • certain antibiotics, such as clarithromycin
    • certain HIV drugs, such as ritonavir (Norvir)
    • omeprazole (Prilosec)
    • esomeprazole (Nexium)
    • cimetidine

What might help

To help prevent dizziness, do not drink grapefruit juice while taking Camzyos. And be sure to check with your doctor or pharmacist before taking any other drugs with Camzyos. This includes over-the-counter medications, herbal remedies, and supplements.

If you have new or worsening dizziness or fainting while taking this drug, talk with your doctor. They may reduce your dosage of Camzyos. They may also order various tests to check your heart function.

Allergic reaction

Like most drugs, Camzyos can cause an allergic reaction in some people. But this side effect wasn’t reported in the drug’s studies. Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, discoloration, or deepening of skin color)
  • swelling under your skin (usually in your eyelids, lips, hands, or feet)
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an oral antihistamine, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Camzyos, they’ll decide whether you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Camzyos, they may have you switch to a different treatment.

Get answers to some frequently asked questions about side effects of Camzyos.

How do side effects of Camzyos compare with those of beta-blockers, such as Coreg?

Coreg (carvedilol) belongs to a group of drugs called beta-blockers. Like Camzyos (which belongs to a group of drugs called cardiac myosin inhibitors), beta-blockers may be prescribed to help reduce symptoms of obstructive hypertrophic cardiomyopathy (HCM).

Camzyos and beta-blockers have some similar and different side effects. For example, both may cause dizziness and heart failure. But beta-blockers can also cause other side effects that aren’t reported with Camzyos, such as fatigue, slow heart rate, and low blood pressure.

To learn more about how Camzyos compares with beta-blockers or other drugs used to treat HCM, talk with your doctor. They can help determine which of these medications is the best treatment option for your condition.

Does Camzyos cause long-term side effects?

Camzyos has a boxed warning for the risk of heart failure, which can have long-term adverse effects. To learn more, see the “Tips for managing side effects” section.

If you’re concerned about this or other possible long-term side effects from this medication, talk with your doctor or pharmacist.

Keeping track of side effects

During Camzyos treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start a new drug or combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Sharing notes with your doctor will help them learn more about how Camzyos affects you. They can then use this information to adjust your treatment plan if needed.

The following is important information you should consider before starting Camzyos.

Boxed warning: Risk of heart failure

Camzyos has a boxed warning for the risk of heart failure. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Tips for managing side effects” section.

Other warnings

Camzyos can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Camzyos is a good treatment option for you.

Talk with your doctor about your health history before starting this medication. Be sure to tell them if any of the following factors apply to you:

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.