This medication is used to treat a certain heart problem (hypertrophic cardiomyopathy). It works by relaxing the muscles in your heart. Mavacamten may help to increase your ability to exercise and improve symptoms such as shortness of breath and tiredness.

Read the Medication Guide provided by your pharmacist before you start taking mavacamten and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor, usually once daily. Swallow the capsules whole. Do not crush or chew the capsules.

The dosage is based on your medical condition, response to treatment, lab tests, and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

To reduce your risk of side effects, your doctor may direct you to start this medication at a low dose and gradually increase your dose. Follow your doctor's instructions carefully.

Avoid eating grapefruit or drinking grapefruit juice while using this medication unless your doctor or pharmacist says you may do so safely. Grapefruit can increase the chance of side effects with this medicine. Ask your doctor or pharmacist for more details.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.

Tell your doctor if your condition lasts or gets worse.

See also Warning section.

Dizziness may occur. If this effect lasts or gets worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Get medical help right away if you have any very serious side effects, including:

• fainting

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking mavacamten, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• other heart problems (such as heart failure, irregular heartbeat)
• current infection

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while taking mavacamten. Mavacamten may harm an unborn baby. Your doctor should order a pregnancy test before you start this medication. Ask about reliable forms of birth control while using this medication and for 4 months after the last dose. See also Drug Interactions section. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Other medications can affect the removal of mavacamten from your body, which may affect how mavacamten works. Examples include azole antifungals (such as itraconazole, ketoconazole), cobicistat, dicloxacillin, efavirenz, esomeprazole, etravirine, fluoxetine, fluvoxamine, moclobemide, drugs used to treat seizures (such as carbamazepine, phenytoin), among others.

This medication can speed up the removal of other medications from your body, which may affect how they work. Examples of affected drugs include elacestrant, quizartinib, revumenib, among others.

This medication may decrease the effectiveness of hormonal birth control such as pills, patch, or ring. This could cause pregnancy. Discuss with your doctor or pharmacist if you should use reliable backup birth control methods while using this medication. Also tell your doctor if you have any new spotting or breakthrough bleeding, because these may be signs that your birth control is not working well.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as echocardiogram) should be done before you start taking this medication and while you are taking it. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.