Camzyos (mavacamten) is a prescription drug that’s 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.

The active ingredient in Camzyos is mavacamten. (An active ingredient is what makes a drug work.) The drug comes as an oral capsule.

Keep reading to learn about the common, mild, and serious side effects Camzyos can cause. For a general overview of the drug, including details about its uses, see this article.

Some people may experience mild to serious side effects during Camzyos treatment. Examples of the drug’s more commonly reported side effects include:

  • dizziness*
  • fainting

* To learn more about this side effect, see the “Side effects explained” section below.

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. And do not stop taking Camzyos unless your doctor recommends it.

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

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after taking Camzyos, but this side effect wasn’t reported in studies.

Serious side effects have been reported with Camzyos. These 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.

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after taking Camzyos, but this side effect wasn’t reported in studies.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Camzyos, visit MedWatch.

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

How do side effects of Camzyos compare with those of similar drugs, 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 used to 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 seen with Camzyos. For example, they may cause fatigue (low energy), 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?

It’s unlikely. Long-term side effects weren’t reported in studies of Camzyos. If you’re concerned about possible long-term side effects from this medication, talk with your doctor or pharmacist.

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:

  • developing a serious infection
  • an irregular heart rhythm
  • drinking grapefruit juice
  • taking medications that interact with Camzyos, especially:

What might help

Due to the risk of heart failure, Camzyos is only available through a risk evaluation and mitigation strategies (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 light-headed or nauseous. Sometimes, dizziness may lead to fainting.

Note that dizziness and fainting are also symptoms of obstructive hypertrophic cardiomyopathy (HCM), which Camzyos is used to treat. They can also be symptoms of heart failure, which is a possible serious side effect of Camzyos. (See section just above to read more about this.)

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, don’t 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 Camzyos, talk with your doctor. They may reduce your dosage of the drug. 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 studies. Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, 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.

Keeping track of side effects

During your 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 taking a new drug or using a 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

Keeping notes and sharing them 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.

Below 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 “Side effects explained” section above.

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:

Alcohol and Camzyos

There are no known interactions between alcohol and Camzyos. But both substances can cause dizziness. So, you may have an increased risk of this side effect if you drink alcohol while taking Camzyos.

If you drink alcohol, talk with your doctor about how much is safe to consume during treatment with this medication.

Pregnancy and breastfeeding with Camzyos

Camzyos is usually only prescribed for someone who’s pregnant or breastfeeding if the benefits of treatment outweigh the potential risks to the fetus or child.

Pregnancy

Camzyos is not safe to take during pregnancy. If you’re pregnant or planning to become pregnant, talk with your doctor about your treatment options.

If you’re able to become pregnant, your doctor may recommend using a form of birth control during your Camzyos treatment. They’ll likely recommend that you use it throughout treatment and for 4 months after treatment ends. Note that Camzyos can make hormonal forms of birth control less effective. Talk with your doctor about your birth control options.

If you become pregnant while taking Camzyos, consider signing up for the Camzyos pregnancy safety study by calling 800-721-5072.

Breastfeeding

It’s not known whether Camzyos is safe to take while breastfeeding. If you’re breastfeeding or planning to do so, talk with your doctor before starting this medication.

Like most drugs, Camzyos can cause a number of side effects that range from mild to serious. But most are temporary and go away after a few days to weeks. If you have questions about side effects that Camzyos can cause, talk with your doctor. Examples of questions to help get you started include:

  • Do other medications I take increase my risk of side effects from Camzyos?
  • Is my risk of side effects higher when I first start Camzyos?
  • How often will I need to have an echocardiogram while taking Camzyos?

To learn more about Camzyos, see these articles:

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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.