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Opsumit is an oral tablet used for pulmonary arterial hypertension. It works by blocking endothelin-1, which helps relax blood vessels and lower blood pressure in the lungs. Common side effects include nasal congestion, sore throat, headache, and low red blood cell levels. Opsumit may cause harm to a fetus if taken during pregnancy. Other serious side effects may include liver damage and fluid retention.

Uses

What is Opsumit used for?

Opsumit (macitentan) is commonly used for pulmonary arterial hypertension (PAH). PAH is a condition where you have high blood pressure in the blood vessels (arteries) that carry blood to your lungs. Over time, this pressure strains your heart and makes it harder for you to be physically active.

Opsumit may also be used for other conditions as determined by your health care provider.

How does Opsumit work (mechanism of action)?

Opsumit blocks endothelin-1, a substance that tightens blood vessels and worsens lung damage in people with pulmonary arterial hypertension. By blocking endothelin-1, Opsumit helps relax the blood vessels and lower the blood pressure in the lungs. This can help prevent the damage from getting worse.

How is Opsumit supplied (dosage forms)?

Brands and other names

  • Opsumit

Dosage forms and strengths

  • 10 mg oral tablets

How should I store Opsumit?

Opsumit should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of Opsumit?

The most common side effects of Opsumit are listed below. Tell your health care provider if you have any of these side effects that bother you.

There may be other side effects of Opsumit that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of Opsumit?

While less common, the most serious side effects of Opsumit are described below, along with what to do if they happen.

Severe Allergic Reactions. Opsumit may cause allergic reactions, which can be serious. Stop taking Opsumit and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking Opsumit. Keep all lab test appointments to monitor for signs of liver problems. Call your health care provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Fluid Retention (Edema). Opsumit can cause fluid retention, also called edema. Fluid retention can cause serious issues in people with certain conditions, such as heart failure. Call your health care provider right away if you have any of the following symptoms.

  • Chest pain
  • Shortness of breath that is worse than usual
  • Stretched or shiny skin
  • Unusual weight gain
  • Swelling of your ankles, legs, belly, or other body areas

Anemia. Opsumit may cause anemia, which is when you have low levels of red blood cells, and low hemoglobin. Hemoglobin is a protein in red blood cells that carries oxygen throughout your body. Tell your health care provider if you have any of the following symptoms of anemia.

  • Unusual weakness or tiredness
  • Cold hands and feet
  • Fast or abnormal heartbeat
  • Pale or yellowish skin 
  • Dizziness, lightheadedness, or feeling like you are about to pass out

Warnings & Precautions

Who should not use Opsumit?

Allergies to Ingredients. People who are allergic to any of the following should not take Opsumit.

  • Macitentan
  • Opsumit
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in Opsumit.

Pregnancy. Do not take Opsumit if you are pregnant or plan to become pregnant. If you become pregnant or think you might be pregnant, contact your health care provider right away. See the Pregnancy section for more details.

What should I know about Opsumit before taking it?

Do not take Opsumit unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share Opsumit with other people, even if they have the same condition as you. It may harm them.

Keep Opsumit out of the reach of children.

Due to Opsumit’s risk of harm to a fetus, people who are able to get pregnant can only get Opsumit through a special program. This program requires taking certain steps to avoid getting pregnant and having monthly pregnancy tests while taking Opsumit. For more information about this program, visit www.MacitentanREMS.com or call 888-572-2934.

Opsumit may lower your sperm count and could make it hard for you to get your partner pregnant. If you have concerns, talk to your health care provider.

What should I tell my health care provider before taking Opsumit?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if Opsumit is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Low levels of red blood cells (anemia)
  • Liver problems
  • Heart failure
  • Pulmonary veno-occlusive disease, a condition where certain blood vessels in the lungs are blocked or narrowed

Other Medicines and Supplements. Opsumit may interact with other medicines and supplements. Before taking Opsumit, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Opsumit may cause harm to a fetus. You must not be pregnant before starting Opsumit. If you can become pregnant, you must take a pregnancy test before starting Opsumit, every month while taking it, and one month after stopping it to make sure you are not pregnant. You must also use a highly effective birth control method (such as tubal ligation) or a combination of methods (such as the pill plus condoms) while taking Opsumit and for one month after your last dose. Talk to your health care provider about your birth control options. If you become pregnant or think you might be pregnant, contact your health care provider right away. 

Breastfeeding. It is not known if Opsumit passes into breast milk. Do not take Opsumit while you are breastfeeding. Tell your health care provider if you are breastfeeding or plan to breastfeed. 

How can I get more information about Opsumit?

For more information about Opsumit, you can visit the drugmaker’s website at www.opsumit.com or call them at 800-526-7736.

Interactions

Does Opsumit interact with foods or drinks?

Your health care provider may recommend limiting or avoiding grapefruit while taking Opsumit. Eating grapefruit or drinking grapefruit juice may raise blood levels of the medicine in your body, which could increase the side effects of Opsumit.

It is unknown if drinking alcohol will affect Opsumit. The risk of side effects, such as headache and liver problems, may be higher if you drink alcohol while taking Opsumit.

Does Opsumit interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking Opsumit.

  • Rifampin (Rifadin), which is a medicine commonly used to treat an infection called tuberculosis
  • Fluconazole (Diflucan), itraconazole (Sporanox, Tolsura), ketoconazole, posaconazole (Noxafil), or voriconazole (Vfend), which are medicines used for fungal infections
  • Amiodarone (Pacerone and others), which is a medicine used for an irregular heart rhythm
  • Any medicine for HIV or AIDS, such as ritonavir (Norvir)

Many other medicines may alter the blood levels of Opsumit. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with Opsumit. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much Opsumit?

If you or someone else has taken too much Opsumit, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of Opsumit?

If you miss a dose, take it as soon as you remember that same day. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.