What are the side effects of Aficamten?
Last updated September 7, 2026.
**Most reported side effects of aficamten are mild, but the effect that matters most is that it can lower your heart's pumping strength too far, which can cause heart failure symptoms.** Aficamten is a cardiac myosin inhibitor used for obstructive hypertrophic cardiomyopathy, and it works by reducing how forcefully the heart squeezes. That is helpful when the heart muscle is too thick, but too much reduction shows up as new shortness of breath, ankle swelling, quick weight gain, tiredness, or fainting. For that reason you get an echocardiogram before you start and on a set schedule afterward, and your dose is raised slowly based on those results. Milder effects people report include dizziness, fatigue, headache, and palpitations. Levels of the drug are changed by several common medicines, so keep one current list of everything you take, including over-the-counter acid reducers, and bring it to every cardiology visit.
What to do
- Keep every echo appointment: The scheduled echocardiograms are how your team catches a drop in pumping strength before you feel it.
- Track four warning signs: New or worse shortness of breath, ankle or leg swelling, weight gain over a few days, and fainting all deserve a same-week call.
- Share your full medicine list: Omeprazole, fluconazole, and some antidepressants change aficamten levels, so include over-the-counter and herbal products.
- Do not stop or double doses: Stopping suddenly can let the obstruction return, so any change should come from your cardiologist.
- Ask about pregnancy plans: If you are pregnant, breastfeeding, or planning a pregnancy, raise it before you start so your team can weigh options.
- Get urgent care for chest pain: Chest pain, fainting, or a racing heart that will not settle needs emergency evaluation, not a wait-and-see approach.
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