Macitentan

This information from UpToDate^® Lexidrug^™ explains what you need to know about this medication, including what it’s used for, how to take it, its side effects, and when to call your healthcare provider.

Brand Names: US

Opsumit

Brand Names: Canada

Opsumit

What is this drug used for?

• It is used to treat high blood pressure in the lungs.

What do I need to tell the doctor BEFORE my child takes this drug?

• If your child is allergic to this drug; any part of this drug; or any other drugs, foods, or substances. Tell the doctor about the allergy and what signs your child had.
• If your child has any of these health problems: Anemia, kidney disease, or liver disease.
• If your child has a health problem called pulmonary veno-occlusive disease (PVOD).
• If your child takes any drugs (prescription or OTC, natural products, vitamins) that must not be taken with this drug, like certain drugs that are used for HIV, infections, seizures, and others. There are many drugs that must not be taken with this drug.

If your child is breast-feeding a baby:

• Be sure your child does not breast-feed a baby while taking this drug.

This is not a list of all drugs or health problems that interact with this drug.

Tell the doctor and pharmacist about all of your child’s drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe to give this drug with all of your child’s other drugs and health problems. Do not start, stop, or change the dose of any drug your child takes without checking with the doctor.

What are some things I need to know or do while my child takes this drug?

• Tell all of your child’s health care providers that your child is taking this drug. This includes your child’s doctors, nurses, pharmacists, and dentists.
• To lower the chance of feeling dizzy or passing out, have your child rise slowly if your child has been sitting or lying down. Have your child be careful going up and down stairs.
• Have your child’s blood work and other lab tests checked as you have been told by the doctor.
• Low red blood cell levels have happened with this drug. Sometimes, this has led to anemia and the need for a blood transfusion. If your child has anemia or you have been told that your child has a low red blood cell level, talk with the doctor.
• Swelling and extra fluid in the body have happened with this drug. Some people have had to take other drugs to treat this. Sometimes, people have had to go to the hospital to be treated for heart failure. Talk with the doctor.
• This drug may lower sperm counts. This may affect being able to father a child. If you have questions, talk with the doctor.
• If your child started taking this drug before puberty, talk with the doctor. Call the doctor right away if breast buds or pubic hair begin to develop or if your child’s period starts.

What are some side effects that I need to call my child’s doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your child’s doctor or get medical help right away if your child has any of the following signs or symptoms that may be related to a very bad side effect:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Signs of liver problems like dark urine, tiredness, decreased appetite, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
• Signs of a urinary tract infection (UTI) like blood in the urine, burning or pain when passing urine, feeling the need to pass urine often or right away, fever, lower stomach pain, or pelvic pain.
• Severe dizziness or passing out.
• Feeling very tired or weak.
• Trouble breathing that is new or worse.
• Shortness of breath, a big weight gain, or swelling in the arms or legs.
• Cough.
• Very heavy periods (menstrual bleeding).

What are some other side effects of this drug?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your child’s doctor or get medical help if any of these side effects or any other side effects bother your child or do not go away:

• Headache.
• Nose or throat irritation.
• Flu-like signs.
• Irritation of the airways (bronchitis).

These are not all of the side effects that may occur. If you have questions about side effects, call your child’s doctor. Call your child’s doctor for medical advice about side effects.

You may report side effects to your national health agency.

How is this drug best given?

Give this drug as ordered by your child’s doctor. Read all information given to you. Follow all instructions closely.

All products:

• Give this drug with or without food.
• Give this drug at the same time of day.
• Keep giving this drug to your child as you have been told by your child’s doctor or other health care provider, even if your child feels well.

Tablets:

• Have your child swallow whole. Do not let your child chew, break, or crush.

Dispersible tablets:

• Wash and dry your hands before and after you give this drug to your child. Do not touch the tablet with wet or damp hands.
• Do not let your child swallow the tablets whole. The tablets must be dissolved in a spoonful or small glass of water before giving.
• To make a suspension using a spoon: Place the tablets needed in a spoon with room temperature water. You may also use orange juice, apple juice, or skim milk. Stir gently for 1 to 3 minutes. Give to your child right away. If water was used, you may mix it further with a small amount of applesauce or yogurt. After giving, add more water, applesauce, or yogurt to the spoon and have your child drink to make sure all of the dose has been taken.
• To make a suspension using a small glass: Place the tablets needed in a glass with a small amount of room temperature water. Stir gently for 1 to 2 minutes. Give to your child right away. After giving, add more water to the glass and have your child drink to make sure all of the dose has been taken.

What do I do if my child misses a dose?

• Give a missed dose as soon as you think about it.
• If it is close to the time for your child’s next dose, skip the missed dose and go back to your child’s normal time.
• Do not give 2 doses at the same time or extra doses.

How do I store and/or throw out this drug?

All products:

• Store at room temperature in a dry place. Do not store in a bathroom.
• Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
• Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.

Dispersible tablets:

• Store in the original package until you are ready to use.

General drug facts

• If your child’s symptoms or health problems do not get better or if they become worse, call your child’s doctor.
• Do not share your child’s drug with others and do not give anyone else’s drug to your child.
• Some drugs may have another patient information leaflet. If you have any questions about this drug, please talk with your child’s doctor, nurse, pharmacist, or other health care provider.
• If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

Consumer Information Use and Disclaimer

This generalized information is a limited summary of diagnosis, treatment, and/or medication information. It is not meant to be comprehensive and should be used as a tool to help the user understand and/or assess potential diagnostic and treatment options. It does NOT include all information about conditions, treatments, medications, side effects, or risks that may apply to a specific patient. It is not intended to be medical advice or a substitute for the medical advice, diagnosis, or treatment of a health care provider based on the health care provider’s examination and assessment of a patient’s specific and unique circumstances. Patients must speak with a health care provider for complete information about their health, medical questions, and treatment options, including any risks or benefits regarding use of medications. This information does not endorse any treatments or medications as safe, effective, or approved for treating a specific patient. UpToDate, Inc. and its affiliates disclaim any warranty or liability relating to this information or the use thereof. The use of this information is governed by the Terms of Use, available at https://www.wolterskluwer.com/en/know/clinical-effectiveness-terms.

Last Reviewed Date

2026-06-19

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