Camzyos (mavacamten) is a prescription medication used to treat obstructive hypertrophic cardiomyopathy (oHCM) in adults. The FDA approved it specifically for people with symptomatic oHCM classified as NYHA class II or III, meaning they experience noticeable limitations during physical activity like shortness of breath, chest pain, or fatigue. It was the first drug designed to target the underlying muscle problem in this condition rather than just managing symptoms indirectly.
What Obstructive Hypertrophic Cardiomyopathy Is
Hypertrophic cardiomyopathy is a condition where the heart muscle becomes abnormally thick, usually in the wall (septum) between the two lower chambers. In the obstructive form, that thickened muscle bulges into the pathway where blood flows out of the heart, partially blocking it. This obstruction forces the heart to work harder to push blood to the rest of the body, which is why people feel short of breath, dizzy, or exhausted during exercise or even routine activities.
The condition affects roughly 1 in 500 people and is mostly genetic. Many people live with it without major symptoms, but the obstructive form can significantly limit daily life. Before Camzyos, the main options were beta blockers, calcium channel blockers, and, for severe cases, surgery or alcohol septal ablation to physically reduce the thickness of the heart muscle.
How Camzyos Works
Camzyos works differently from older heart medications. It directly targets the protein that makes heart muscle cells contract, called cardiac myosin. In oHCM, too many of these myosin molecules are in an active, power-generating state at any given time, causing the muscle to contract too forcefully and stiffen excessively.
Camzyos reduces the number of myosin molecules that shift into that active state and pushes more of them into a resting, energy-saving configuration. The result is a heart that contracts with less excessive force, which reduces the obstruction in the outflow tract and lets blood flow more freely. Because it addresses the root mechanical problem, it can improve both exercise capacity and day-to-day symptoms like breathlessness and fatigue.
Where It Fits in Treatment
The 2024 guidelines from the American Heart Association and American College of Cardiology give Camzyos (and myosin inhibitors as a class) a Class 1 recommendation, the strongest level. That recommendation applies to adults with obstructive HCM who still have symptoms despite taking beta blockers or calcium channel blockers. In practice, this means Camzyos is typically added when first-line medications aren’t providing enough relief, and it can serve as an alternative to invasive procedures like septal myectomy surgery.
What Taking Camzyos Looks Like
Camzyos is a once-daily capsule taken by mouth, with or without food. The starting dose is 5 mg. Because the drug takes weeks to reach its full effect in the body, dose adjustments happen gradually. At week 4, your doctor will use an echocardiogram to measure how much obstruction remains in the heart’s outflow tract, then decide whether to keep the dose the same, lower it to 2.5 mg, or raise it to 10 mg.
After the initial adjustment period, monitoring continues every 12 weeks. The dose can be gradually increased up to a maximum of 15 mg per day if symptoms and obstruction persist, as long as the heart’s pumping function stays strong. This step-by-step approach is essential because the drug’s main risk is reducing heart function too much.
The Key Safety Concern
Camzyos carries a boxed warning, the FDA’s most serious safety label, related to heart failure. Because the drug deliberately reduces how forcefully the heart contracts, it can occasionally lower the heart’s pumping ability (measured as left ventricular ejection fraction, or LVEF) below safe levels. If LVEF drops below 50% at any point, treatment is paused. If it drops below 50% a second time on the lowest dose (2.5 mg), the medication is permanently discontinued.
Starting Camzyos is not recommended if your ejection fraction is already below 55%. This is why regular echocardiograms are a non-negotiable part of being on this medication. The monitoring schedule is built into the prescribing requirements, so you should expect frequent imaging appointments, especially in the first few months.
Drug Interactions and Contraindications
Camzyos is processed in the liver by specific enzymes, and medications that speed up or slow down those enzymes can significantly change how much Camzyos is active in your body. Certain antifungal medications, some antibiotics, and even grapefruit juice can increase drug levels to a dangerous degree. On the other hand, some seizure medications and the herbal supplement St. John’s wort can reduce its effectiveness. Your prescribing team will carefully review your full medication list before starting treatment and at every dose change.
Camzyos is contraindicated during pregnancy due to potential harm to the developing fetus. The 2024 AHA/ACC guidelines classify its use in pregnant women as “Class 3: Harm,” meaning it should not be used under any circumstances during pregnancy.
What to Expect in Terms of Results
Because Camzyos takes weeks to build up in the body, you won’t feel a dramatic change in the first few days. Most people begin noticing improvements in exercise tolerance and daily symptoms over the first several weeks as the dose is optimized. The clinical trials that led to its approval showed meaningful reductions in the pressure gradient across the heart’s outflow tract, which translated to patients being able to do more physical activity with fewer symptoms.
For many people with oHCM, Camzyos represents a significant shift: a medication that targets the disease itself rather than just blunting the heart rate or relaxing blood vessels. It doesn’t cure the condition or reverse the thickening of the heart muscle, but it can substantially reduce the obstruction that causes the most debilitating symptoms.