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Generic Name: Macitentan (ma si TEN tan)
Brand Name: Opsumit

Medically reviewed by Last updated on Nov 14, 2020.


  • This medicine may cause harm to the unborn baby if you take it while you are pregnant.
  • Do not take Opsumit (macitentan) if you are pregnant. A pregnancy test will be done to show that you are NOT pregnant before starting Opsumit (macitentan).
  • A pregnancy test will be done every month during treatment and for 1 month after the last dose.
  • Use 2 kinds of birth control during treatment and for 1 month after your last dose.
  • If you get pregnant while taking Opsumit (macitentan) or within 1 month after your last dose, call your doctor right away.

Uses of Opsumit:

What do I need to tell my doctor BEFORE I take Opsumit?

  • If you have an allergy to macitentan or any other part of Opsumit (macitentan).
  • If you are allergic to Opsumit (macitentan); any part of Opsumit (macitentan); or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you have anemia.
  • If you have a health problem called pulmonary veno-occlusive disease (PVOD).
  • If you take any drugs (prescription or OTC, natural products, vitamins) that must not be taken with Opsumit (macitentan), like certain drugs that are used for HIV, infections, or seizures. There are many drugs that must not be taken with Opsumit (macitentan).
  • If you are breast-feeding. Do not breast-feed while you take Opsumit (macitentan).

This is not a list of all drugs or health problems that interact with Opsumit (macitentan).

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Opsumit (macitentan) with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take Opsumit?

For all patients taking Opsumit (macitentan):

  • Tell all of your health care providers that you take Opsumit (macitentan). This includes your doctors, nurses, pharmacists, and dentists.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • Low red blood cell levels have happened with Opsumit (macitentan). Sometimes, this has led to anemia and the need for a blood transfusion. If you have anemia or have been told that you have a low red blood cell level, talk with your doctor.
  • Swelling and extra fluid in the body have happened with Opsumit (macitentan). 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 medicine may lower sperm counts in men. This may affect being able to father a child. Talk with the doctor.
  • If you are a woman and you miss a period, have unprotected sex, or think that your birth control has not worked, call your doctor right away.


  • If your child started taking Opsumit (macitentan) before puberty, talk with the doctor. Call the doctor right away if breast buds or pubic hair begin to develop or if your child starts her menstrual period.

How is this medicine (Opsumit) best taken?

Use Opsumit (macitentan) as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • Take with or without food.
  • Swallow whole. Do not chew, break, or crush.
  • Keep taking Opsumit (macitentan) as you have been told by your doctor or other health care provider, even if you feel well.

What do I do if I miss a dose?

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

What are some side effects that I need to call my 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 doctor or get medical help right away if you have 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, feeling tired, not hungry, 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.
  • 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.

What are some other side effects of Opsumit?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you 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 doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at

If OVERDOSE is suspected:

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.

How do I store and/or throw out Opsumit?

  • Store at room temperature.
  • Store 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.

Consumer information use

  • If your symptoms or health problems do not get better or if they become worse, call your doctor.
  • Do not share your drugs with others and do not take anyone else's drugs.
  • This medicine comes with an extra patient fact sheet called a Medication Guide. Read it with care. Read it again each time Opsumit (macitentan) is refilled. If you have any questions about Opsumit (macitentan), please talk with the doctor, 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.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.