Aficamten: treating obstructive HCM, dosing, and side effects
Last updated September 7, 2026.
**Aficamten is a prescription tablet in a class called cardiac myosin inhibitors, used for obstructive hypertrophic cardiomyopathy (HCM).** In obstructive HCM the heart muscle is thickened and squeezes too forcefully, which narrows the path blood takes out of the heart. Aficamten reduces that excess squeezing so the outflow tract opens up, which usually eases breathlessness and improves exercise capacity. The safety point that drives everything else: aficamten can lower your heart's pumping strength too much, so you need an echocardiogram before you start and at set points afterward, and every dose change is based on those results.
What does it treat?
Aficamten is used in adults with symptomatic obstructive hypertrophic cardiomyopathy, meaning the thickened muscle is blocking blood flow out of the left ventricle and you have symptoms because of it. The typical picture is shortness of breath with stairs, hills, or housework, chest tightness or pressure on exertion, lightheadedness when you stand up fast or after a large meal, palpitations, and sometimes fainting. Doctors confirm the pattern with an echocardiogram that measures the left ventricular outflow tract gradient at rest and with provocation, such as after a Valsalva maneuver or exercise. Aficamten is usually added when symptoms persist despite a beta blocker, verapamil, or diltiazem, and it is often continued alongside those medicines. It is not a treatment for nonobstructive HCM, for high blood pressure, or for ordinary heart failure, and it comes as a single ingredient tablet with no combination products.
How do you take it?
Aficamten comes as tablets taken once daily, with or without food, at about the same time each day. The label starts most adults at 5 mg once daily, then your doctor rechecks an echocardiogram and can step the dose up through 10 mg, 15 mg, and 20 mg once daily based on your outflow tract gradient and your ejection fraction; 20 mg once daily is the ceiling. Doses are not adjusted by how you feel alone, since the echo numbers decide, and your doctor may hold or lower the dose if your ejection fraction drops below the label's threshold or your gradient falls too far. Swallow the tablet whole with water rather than crushing or splitting it. If you miss a dose, take it that same day when you remember, and if it is already close to the next day's dose, skip the missed one and go back to your usual schedule; never take two doses in one day. Do not stop or restart aficamten on your own, because stopping changes your heart's function too, and call your doctor before the next dose if you develop new or worsening shortness of breath, swelling in your legs, sudden weight gain, or fainting.
Side effects to know
- Common: Many people notice no day to day effects, and the ones most often reported are dizziness or lightheadedness, tiredness, and headache, with the main expected effect being the drop in pumping strength that shows up on your echocardiogram rather than as a symptom.
- Serious: Stop and get medical help the same day if you develop signs of heart failure from reduced pumping strength: new or worsening shortness of breath, trouble breathing when lying flat, waking up short of breath, swelling in the legs or belly, or a weight gain of several pounds over a few days. Fainting, near fainting, chest pain, or a fast irregular heartbeat that does not settle also needs urgent evaluation, since atrial fibrillation and low blood pressure can appear on this medicine.
Who should not take it?
Aficamten is not started if your ejection fraction is already below the label's cutoff, and it is not for people with nonobstructive HCM. Tell your doctor about every medicine and supplement you take, because aficamten is broken down by the CYP2C19 and CYP3A4 enzymes: strong inhibitors such as omeprazole, esomeprazole, fluvoxamine, fluconazole, ketoconazole, itraconazole, clarithromycin, and ritonavir raise your levels, and inducers such as rifampin, carbamazepine, phenytoin, and St. John's wort lower them, so doses often need changing or the combination is avoided. Be careful with medicines that reduce blood volume or relax blood vessels, including diuretics, nitrates, and drugs for erectile dysfunction, since they can worsen the outflow obstruction. Dehydration, vomiting, diarrhea, fever, or a long stretch of heavy sweating can do the same, so call your doctor rather than pushing through. Keep alcohol light or skip it, because alcohol dilates blood vessels and dehydrates you, and it can trigger dizziness or fainting in obstructive HCM. Aficamten can harm a developing baby based on animal studies, so it is not recommended during pregnancy; if you can become pregnant, use effective contraception and tell your doctor right away if you become pregnant or plan to. There is no information on aficamten in breast milk, so discuss feeding plans before you start.
When is it an emergency?
Call 911 in the US if you collapse or faint, cannot catch your breath, have chest pain or pressure that lasts more than a few minutes, or have a heartbeat so fast or irregular that you feel faint. Sudden severe shortness of breath, pink or frothy sputum, or breathlessness that forces you to sit upright to breathe can mean acute heart failure and needs an emergency room, not a next day appointment. Signs of a severe allergic reaction, such as swelling of the lips, tongue, or throat, hives with trouble breathing, or sudden dizziness, are also a 911 call. For a suspected overdose, or if someone takes extra tablets by mistake, call Poison Control at 1-800-222-1222 right away; too much aficamten can drop the heart's pumping strength and blood pressure, causing severe weakness, fainting, and shortness of breath. Bring your dose and the date of your last echocardiogram with you, since that information changes how the emergency team treats you.
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Common questions
What is the maximum dose of aficamten?
The highest dose in the label is 20 mg once daily. Most people start at 5 mg once daily and move up in steps through 10 mg and 15 mg, with an echocardiogram checked before each increase. Your doctor raises the dose only if your outflow tract gradient is still high and your ejection fraction is safely above the label's cutoff. Never increase your own dose to get faster symptom relief, because the drug's benefit and its main risk both come from the same effect on heart squeeze.
Can I drink alcohol while taking aficamten?
Keep it light or skip it. Alcohol widens blood vessels and dehydrates you, and both of those worsen the outflow obstruction in HCM, so a couple of drinks can bring on dizziness, palpitations, or fainting that you would not get otherwise. There is no direct chemical clash between alcohol and aficamten, but the combined effect on blood pressure is the problem. If you do drink, have water alongside it, stay seated for a while before standing, and stop entirely if you have ever fainted with this condition.
Should I take aficamten with food?
You can take it with or without food, so pick whatever helps you remember. Take it at roughly the same time each day, and swallow the tablet whole with water instead of crushing or splitting it. What matters much more than food is what else you take with it: acid reducers like omeprazole and esomeprazole block the enzyme that clears aficamten and can raise your levels, so check with your doctor before starting any over the counter heartburn medicine. Bring your full medicine list, including supplements, to every visit.
Is aficamten safe during pregnancy or breastfeeding?
It is not recommended in pregnancy. Animal studies showed harm to the developing fetus, so people who can become pregnant are advised to use effective contraception while taking it. Tell your doctor as soon as you are pregnant or are planning to be, since your HCM treatment plan will need to change and pregnancy itself puts extra demand on the heart. There is no information on whether aficamten passes into breast milk, so talk through feeding plans before you start rather than after the baby arrives.
What happens if I take too much aficamten?
Too much of it lowers the heart's pumping strength and blood pressure more than intended. Watch for severe weakness, marked shortness of breath, lightheadedness, fainting, or a heartbeat that feels fast and weak. Call Poison Control at 1-800-222-1222 right away if you or someone else takes extra tablets, even if there are no symptoms yet, and call 911 if there is collapse or trouble breathing. Do not try to correct it by skipping the next several doses on your own, since stopping abruptly has its own effects; let your doctor set the plan.
Which medicines interact with aficamten?
Aficamten is cleared by the CYP2C19 and CYP3A4 enzymes, so drugs that block those enzymes raise your levels and increase the risk of your ejection fraction dropping. That list includes omeprazole, esomeprazole, fluvoxamine, fluconazole, ketoconazole, itraconazole, clarithromycin, and ritonavir. Drugs that speed those enzymes up, such as rifampin, carbamazepine, phenytoin, and St. John's wort, can make aficamten less effective. Separately, diuretics, nitrates, and erectile dysfunction drugs can worsen the outflow obstruction by dropping blood volume or dilating vessels. Check with your doctor or pharmacist before adding anything new, including supplements.
Why do I need so many echocardiograms on this medicine?
The echo is how your doctor sees both halves of the picture: whether the outflow tract gradient has come down enough to help your symptoms, and whether your ejection fraction has fallen too far. Symptoms alone cannot tell you that, because a falling ejection fraction can be silent at first. You get a baseline echo before your first dose, then repeat scans around each dose change and at intervals afterward. If your ejection fraction drops below the label's threshold, your doctor lowers or holds the dose until it recovers.