Mavacamten is used in adults to treat a heart problem called obstructive hypertrophic cardiomyopathy (HCM). mavacamten may improve people's symptoms and their ability to be active.

Mavacamten is available only from a certified pharmacy under a special program. You must be registered in the program and understand the risks and benefits of this medicine.

Mavacamten may also be used for purposes not listed in this medication guide.

Call your doctor at once if you have shortness of breath, chest pain, tiredness, swelling in your legs, rapid weight gain, or racing or pounding heartbeats.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Talk to your doctor before changing your dose.

You should get an echocardiogram before and during treatment with mavacamten.

Take mavacamten once a day.

Swallow the capsule whole and do not crush, chew, break, or open it.

Your treatment may be delayed or permanently discontinued if you have certain side effects.

Store at room temperature away from moisture and heat.

Usual Adult Dose for Hypertrophic Cardiomyopathy:

Starting dose: 5 mg orally once a day
Allowable subsequent doses with titration: 2.5, 5, 10, or 15 mg orally once a day

Comments:
-Patients may develop heart failure while taking this drug; regular left ventricular ejection fraction (LVEF) and Valsalva left ventricular outflow tract (LVOT) gradient assessment is needed for careful titration to achieve an appropriate target Valsalva LVOT gradient, while maintaining LVEF at least 50% and avoiding heart failure symptoms.
-When initiating or titrating this drug, LVEF should be considered first, then the Valsalva LVOT gradient and patient clinical status should be considered to guide appropriate dosing; the algorithms for INITIATION and MAINTENANCE should be followed for appropriate dosing and monitoring schedules.
-If LVEF is less than 50% during therapy, this drug should be interrupted; the algorithm for INTERRUPTION should be followed for guidance on interrupting, restarting, or discontinuing this drug. If interrupted at 2.5 mg, the patient should either restart at 2.5 mg or permanently discontinue this drug.

Use: For the treatment of patients with symptomatic New York Heart Association (NYHA) class II to III obstructive hypertrophic cardiomyopathy (HCM) to improve functional capacity and symptoms

Some drugs should not be used with mavacamten. Your treatment plan may change if you also use:

• nefazodone;

• St. John's wort;

• an antibiotic--clarithromycin, rifabutin, rifampin, rifapentine, telithromycin;

• antifungal medicine--itraconazole, ketoconazole;

• antiviral medicine for HIV or hepatitis C--boceprevir, cobicistat, dasabuvir, elvitegravir, indinavir, lopinavir/ritonavir, nelfinavir, ombitasvir, paritaprevir saquinavir, telaprevir, tipranavir;

• cancer medicine--apalutamide, enzalutamide, mitotane;

• seizure medicine--carbamazepine, oxcarbazepine, phenytoin, primidone;

• steroid medicine--dexamethasone, prednisone;

Tell your doctor if you have ever had:

• an irregular heartbeat; or

• if you have an infection.

Mavacamten may harm an unborn baby. You may need a pregnancy test to make sure you are not pregnant. Use effective birth control while using mavacamten and for at least 4 months after your last dose. Tell your doctor if you become pregnant.

Ask a doctor if it is safe to breastfeed while using mavacamten.

Mavacamten can make birth control pills less effective. Ask your doctor about other birth control options such as an injection, implant, skin patch, vaginal ring, condom, diaphragm, cervical cap, or contraceptive sponge.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

Unless your doctor tells you otherwise, continue your normal diet.

Grapefruit may interact with mavacamten and cause side effects. Avoid consuming grapefruit products.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Mavacamten may cause serious side effects. Call your doctor at once if you have:

• heart failure symptoms--shortness of breath, chest pain, tiredness, swelling in your legs, rapid weight gain, or racing or pounding heartbeats.

Common side effects of mavacamten may include:

• dizziness; or

• fainting.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all your other medicines, especially:

• other medicines to treat obstructive hypertrophic cardiomyopathy; or

• omeprazole, esomeprazole, or cimetidine.

This list is not complete. Other drugs may affect mavacamten, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.