Camzyos (mavacamten) is a prescription medication used to treat symptomatic obstructive hypertrophic cardiomyopathy (HCM) in adults. It carries an FDA boxed warning for heart failure risk, and it’s only available through a restricted safety program because of that risk.
Camzyos Boxed Warning: Heart Failure Risk
Camzyos works by reducing the excessive contraction of the heart muscle that causes obstructive HCM, but that same mechanism can reduce left ventricular ejection fraction (LVEF) — a measure of how well the heart pumps — too much in some patients, leading to heart failure due to systolic dysfunction. This is a boxed warning, the FDA’s strongest safety warning, though the event was reported as rare in clinical trials.
Because of this risk, Camzyos is available only through the CAMZYOS REMS Program (Risk Evaluation and Mitigation Strategy). Prescribers, pharmacies, and patients must all be enrolled. The program requires:
- An echocardiogram (LVEF check) before starting treatment
- Periodic echocardiograms during treatment to monitor LVEF
- Screening for interacting medications at every visit
Starting Camzyos is not recommended if LVEF is already below 55%, and treatment is interrupted if LVEF drops below 50% at any point, or if a patient develops heart failure symptoms or a worsening clinical status.
Common Camzyos Side Effects
The most commonly reported side effects include:
- Dizziness
- Fainting (syncope), which can increase the risk of falls and injury
- Shortness of breath
Anyone who feels lightheaded, dizzy, or faint while taking Camzyos should sit or lie down immediately to avoid a fall, and report the symptom to their prescriber.
Drugs That Increase Camzyos Risk
Certain medications raise the risk of heart failure when combined with Camzyos, and the REMS program specifically screens for them at every visit. These include:
- Disopyramide (Norpace)
- Ranolazine (Ranexa)
- Verapamil (Verelan) or diltiazem (Cardizem CD) taken together with a beta-blocker such as metoprolol (Lopressor)
Patients with an existing heart condition, including a prior history of heart failure, are also at higher risk and require closer monitoring. This is general information, not medical advice — never start, stop, or combine medications with Camzyos without checking with the prescribing cardiologist first, since interactions here carry a boxed-warning-level risk.
Frequently Asked Questions
Why does Camzyos require an echocardiogram before every dose change?
Because Camzyos directly affects how forcefully the heart contracts, its dose is individually titrated based on LVEF and symptom response. Echocardiograms let the prescriber confirm the heart is still pumping safely before increasing or continuing the dose.
Is Camzyos a beta-blocker?
No. Camzyos is a cardiac myosin inhibitor, a different drug class that works directly on the heart muscle’s contractile proteins. It’s sometimes used alongside beta-blockers, but the combination requires closer monitoring due to added heart failure risk.
Can Camzyos be taken during pregnancy?
Camzyos can cause fetal harm, so it’s not recommended during pregnancy, and effective contraception is generally required during treatment and for a period after stopping. Anyone who is pregnant or planning pregnancy should discuss this directly with their cardiologist.