Camzyos (mavacamten) is a daily capsule for obstructive hypertrophic cardiomyopathy (HCM). It relaxes an overly strong heart muscle, but because it can weaken the heart too much, it carries a boxed warning for heart failure and needs regular echocardiograms.
- What it treats: symptomatic obstructive HCM, to improve exercise capacity and symptoms such as breathlessness, chest pain and tiredness. Since September 2026 it is approved for children and teenagers weighing at least 30 kg as well as adults.
- How it works: it is the first cardiac myosin inhibitor. It reduces the excess force of each heartbeat, which eases the blockage (obstruction) that thickened heart muscle causes.
- The main risk: heart failure from too much weakening of the heart’s pumping (systolic dysfunction). Your ejection fraction is checked by echocardiogram before and during treatment, and the drug is paused if it falls below 50%.
- Restricted program: prescribers, pharmacies and patients must all enroll in the Camzyos REMS (Risk Evaluation and Mitigation Strategy) Program.
- Common side effects: dizziness and fainting are the ones seen more often than with placebo.
- Interactions matter a lot: several common drugs, including omeprazole and some antifungals and antibiotics, raise Camzyos levels and the risk of heart failure.
This is general information, not medical advice. Camzyos is started and adjusted only by a cardiologist through the REMS program. Never start, stop or change any medicine, including over-the-counter ones, without checking with your heart team.
Camzyos at a glance
| Details | |
|---|---|
| Generic name | Mavacamten |
| Drug class | Cardiac myosin inhibitor |
| Made by | Bristol Myers Squibb |
| First US approval | April 2022 (adults); September 2026 (children weighing 30 kg or more) |
| Form | Capsules: 1 mg, 2.5 mg, 5 mg, 10 mg and 15 mg |
| Usual adult starting dose | 5 mg once daily, adjusted by echocardiogram to 2.5, 5, 10 or 15 mg |
| Boxed warning | Risk of heart failure due to systolic dysfunction |
| Access | Only through the Camzyos REMS Program |
| Monitoring | Echocardiograms at the start, at weeks 4, 8 and 12, then every 3 to 6 months |
| Pregnancy | May harm a fetus; effective contraception required |
What is obstructive hypertrophic cardiomyopathy?
Hypertrophic cardiomyopathy is an inherited condition in which the walls of the heart’s main pumping chamber, the left ventricle, become abnormally thick. It affects roughly 1 in 500 people, although many are never diagnosed. In about two-thirds of people, the thickened wall near the outflow of the heart bulges into the path of blood leaving the heart. The mitral valve can also be pulled into that path during each beat. Together they create an obstruction, measured as a pressure gradient across the left ventricular outflow tract (LVOT).
Obstruction makes the heart work harder and can cause breathlessness on exertion, chest pain, palpitations, dizziness and fainting. At the cellular level, HCM is often driven by gene variants in heart muscle proteins, especially myosin, that make the muscle contract too forcefully and relax poorly.
Before Camzyos, treatment relied on beta-blockers, verapamil or diltiazem, and disopyramide to ease symptoms, and on septal reduction therapy (surgical myectomy or alcohol septal ablation) to remove or shrink the thickened muscle. None of the medicines targeted the underlying problem of excess contraction.
How Camzyos works
Heart muscle contracts when myosin “heads” grab onto actin filaments and pull. In HCM, too many myosin heads are available and active at once, producing an overly strong, energy-hungry contraction.
Mavacamten binds to cardiac myosin and shifts more of the heads into a resting “super-relaxed” state, so fewer are available to pull. The result is a gentler contraction, less obstruction in the outflow tract and better filling of the heart between beats. In trials, the outflow gradient began falling within the first few weeks of treatment.
The same effect explains the main risk. If too many myosin heads are switched off, the heart’s pumping strength (ejection fraction) falls too far and heart failure can develop. That is why the dose is guided by echocardiograms rather than set at a standard amount.
How Camzyos is dosed and monitored
For adults, treatment usually starts at 5 mg once daily. Your cardiologist then adjusts the dose step by step (2.5, 5, 10 or 15 mg) based on two measurements on your echocardiogram:
- Left ventricular ejection fraction (LVEF): how well the heart pumps. Normal in HCM is typically 60% or higher.
- Valsalva LVOT gradient: the outflow obstruction while you bear down, which makes obstruction worse.
The label rules are strict:
- Starting Camzyos is not recommended if LVEF is below 55%.
- Treatment is interrupted if LVEF falls below 50% at any visit, or if you develop heart failure symptoms or your clinical condition worsens. It can restart at a lower dose once LVEF recovers to 50% or more.
- Treatment is permanently stopped if LVEF falls below 50% twice on the lowest dose.
- Doses are only increased when LVEF is at least 55% and the Valsalva gradient is still 30 mmHg or more.
Echocardiogram schedule
Under the April 2025 update to the REMS program, echocardiograms are required:
- before treatment starts
- at 4, 8 and 12 weeks after starting
- every 3 to 6 months after that, depending on your results
- 4 and 12 weeks after any dose change, after a treatment break, and after starting certain interacting medicines
Before 2025, the maintenance schedule was every 12 weeks. The change to every 3 to 6 months for stable patients was based on longer-term safety data.
Children and teenagers
In September 2026 the FDA extended the approval to children weighing at least 30 kg (about 66 lb), based on the SCOUT-HCM trial in 44 patients aged 12 to 18. Mavacamten significantly lowered the Valsalva outflow gradient compared with placebo over 28 weeks. Children can start on lower doses, and the lowest pediatric dose is 1 mg.
The boxed warning: heart failure
Camzyos lowers ejection fraction in everyone who takes it; that is how it works. In most people the fall is modest and the heart still pumps normally. In some, it falls far enough to cause heart failure due to systolic dysfunction, which can be serious or life-threatening.
The risk is higher if:
- you start or increase an interacting medicine (see below)
- you develop a serious illness, such as an infection or a fast irregular heartbeat like atrial fibrillation
- you have heart surgery or another major procedure
Seek medical help straight away if you notice worsening shortness of breath, breathlessness when lying flat, swelling of the legs or ankles, rapid weight gain, a fast or irregular heartbeat, or feeling faint. Tell your cardiologist about any new illness, since they may pause the drug.
The Camzyos REMS Program
Because of the heart failure risk, Camzyos is not available at ordinary pharmacies. Under the REMS:
- Prescribers must be certified and must confirm your echocardiogram results before each prescription can continue.
- Patients must enroll, receive the patient brochure and keep up with echocardiograms. If you miss the required scans, you will not be able to keep getting the drug.
- Pharmacies must be certified, check for interacting drugs before every dispense and only supply authorized patients.
It sounds bureaucratic, but the program exists so that the drug’s main risk is caught early.
Drug interactions: why they matter so much
Mavacamten is broken down by two liver enzymes, CYP2C19 and CYP3A4. Drugs that block these enzymes raise mavacamten levels and the risk of heart failure. Drugs that speed them up lower its levels and can make it stop working. Your genes matter too: people who are “poor metabolizers” through CYP2C19 clear the drug much more slowly.
| Type of drug | Examples | What the label says |
|---|---|---|
| Moderate to strong CYP2C19 inhibitors | Fluconazole, fluvoxamine, ticlopidine | Contraindicated |
| Strong CYP3A4 inhibitors | Clarithromycin, itraconazole, ketoconazole, ritonavir | Contraindicated |
| Moderate to strong CYP2C19 or CYP3A4 inducers | Rifampin, carbamazepine, phenytoin, St John’s wort | Contraindicated (can stop Camzyos working) |
| Weak CYP2C19 inhibitors | Omeprazole, esomeprazole, cimetidine | Reduce Camzyos by one dose level when starting; extra echos |
| Moderate CYP3A4 inhibitors | Diltiazem, verapamil, erythromycin | Reduce Camzyos by one dose level when starting; extra echos |
| Negative inotropes | Disopyramide, plus beta-blockers or verapamil together | Extra caution; can add to the drop in heart function |
Two points catch people out. First, heartburn medicines like omeprazole and esomeprazole are sold over the counter, but they need a Camzyos dose reduction. Second, stopping an inhibitor can let mavacamten levels fall, so changes in either direction need your cardiologist’s input.
Hormonal contraception
Mavacamten may reduce the effectiveness of combined hormonal contraceptives. The label advises a contraceptive method that is not affected by CYP3A4 induction (such as an intrauterine device) or adding a non-hormonal method. This matters because mavacamten may harm a developing baby. Use effective contraception during treatment and for 4 months after the last dose.
How well does Camzyos work?
EXPLORER-HCM
This phase 3 trial enrolled 251 adults with symptomatic obstructive HCM. The main goal was a combined improvement in exercise capacity (peak oxygen uptake) and symptoms (NYHA class). After 30 weeks, 37% of people on mavacamten met the goal, compared with 17% on placebo. Outflow gradients fell substantially, symptoms and quality-of-life scores improved, and NT-proBNP, a blood marker of heart strain, dropped. When the drug was stopped for 8 weeks at the end of the study, ejection fraction returned to baseline.
VALOR-HCM
This trial asked a practical question: can mavacamten spare people from septal reduction surgery? It enrolled 112 adults with severe symptoms who were already referred for myectomy or alcohol septal ablation. After 16 weeks, only 17.9% of people on mavacamten still met guideline criteria for, or chose to go ahead with, the procedure, compared with 76.8% on placebo. Many people on mavacamten were able to avoid or postpone surgery.
Side effects
Most people tolerate Camzyos well. In the adult trials, dizziness and fainting (syncope) were the side effects seen more often than with placebo. Shortness of breath was also reported slightly more often (about 12% vs 9% in the phase 3 studies). The more important “side effect” is the planned drop in ejection fraction, which is why monitoring is built into every step.
Who should not take Camzyos
- people with an ejection fraction below 55% at the start
- people who must take one of the contraindicated interacting medicines
- people who are pregnant or trying to become pregnant
- people with non-obstructive HCM: the FDA approval covers obstructive HCM only
If you have had atrial fibrillation, your cardiologist will want it well controlled, since a fast irregular rhythm can tip a weakened heart into failure.
Camzyos vs other HCM treatments
| Treatment | What it does | Role |
|---|---|---|
| Beta-blockers, verapamil, diltiazem | Slow the heart and improve filling | First-line symptom control |
| Disopyramide | Reduces contraction force and obstruction | Added when first-line drugs are not enough |
| Mavacamten (Camzyos) | Reduces excess myosin activity and obstruction | For symptoms despite first-line drugs; can delay or avoid surgery |
| Septal myectomy | Surgically removes thickened muscle | Very effective at experienced centres |
| Alcohol septal ablation | Shrinks thickened muscle via a catheter | Alternative to surgery in selected people |
Current American Heart Association and American College of Cardiology guidance places cardiac myosin inhibitors after beta-blockers or calcium channel blockers for adults whose symptoms persist. Septal reduction remains the definitive option for many, especially at high-volume centres. Mavacamten does not remove the need for an implantable defibrillator in people at high risk of sudden death, and it is not a cure.
Living with Camzyos: practical tips
- Never skip echocardiograms. Book the next one before you leave each appointment.
- Carry a medication card that says you take mavacamten, so emergency doctors know about the interaction risks.
- Check with your pharmacist before buying heartburn tablets, antifungals or herbal remedies.
- Call your cardiologist if you get ill with a fever, vomiting or a fast heartbeat; a short pause may be safer.
- Keep track of symptoms like breathlessness and swelling between visits.
- Ask about cost support. Bristol Myers Squibb runs a patient support program for eligible patients.
Frequently asked questions
What is Camzyos used for?
Camzyos (mavacamten) treats symptomatic obstructive hypertrophic cardiomyopathy, to improve exercise capacity and symptoms. It is approved for adults and, since September 2026, for children weighing at least 30 kg.
Why does Camzyos have a boxed warning?
Because it reduces the heart’s pumping strength and can cause heart failure due to systolic dysfunction. Echocardiograms are required before and during treatment, and the drug is paused if ejection fraction falls below 50%.
How often do you need an echocardiogram on Camzyos?
Before starting, at 4, 8 and 12 weeks, then every 3 to 6 months depending on results. Extra echos are needed 4 and 12 weeks after dose changes, treatment breaks or starting certain interacting medicines.
Can I take omeprazole with Camzyos?
Omeprazole, esomeprazole and cimetidine are weak CYP2C19 inhibitors. Under the current label they are not forbidden, but Camzyos should be reduced by one dose level when starting them, with extra echocardiograms. Always check with your cardiologist first.
What are the side effects of Camzyos?
Dizziness and fainting were seen more often than with placebo. The most important risk is heart failure from too much reduction in heart pumping, which is why ejection fraction is monitored.
Can Camzyos replace septal myectomy?
For some people it can delay or avoid surgery. In the VALOR-HCM trial, far fewer people on mavacamten still needed or chose septal reduction therapy after 16 weeks. Surgery remains the definitive option for many, and the choice should be made with an HCM specialist.
What is the Camzyos REMS Program?
A safety program required by the FDA. Prescribers, pharmacies and patients must enroll; echocardiogram results must be confirmed to continue treatment, and pharmacies check for drug interactions before every dispense.
References
- Bristol Myers Squibb. CAMZYOS (mavacamten) US prescribing information
- FDA. CAMZYOS prescribing information, revised 4/2025 (Drugs@FDA)
- FDA. CAMZYOS REMS Program document, April 2025
- FDA. FDA approves first drug to improve functional capacity and symptoms in children with rare inherited heart condition, 2026
- European Medicines Agency. Camzyos summary of product characteristics
- Olivotto I, et al. Mavacamten for treatment of symptomatic obstructive hypertrophic cardiomyopathy (EXPLORER-HCM). Lancet. 2020;396:759-769
- Desai MY, et al. Myosin inhibition in patients with obstructive hypertrophic cardiomyopathy referred for septal reduction therapy (VALOR-HCM). J Am Coll Cardiol. 2022;80:95-108
About this article
Written by the Health Linear Editorial Team from primary sources such as FDA prescribing information, DailyMed, NIH and peer-reviewed studies, which are linked in the article. Last updated October 30, 2026.
Read our editorial process and medical disclaimer. Spotted an error? Tell us and we will correct it.