Opsumit (macitentan) is a medication for treating people with pulmonary arterial hypertension (PAH), or high blood pressure in the blood vessels in the lungs. It can be used alone or together with other PAH medications. Opsumit (macitentan) has several benefits, including lowering the risk of worsening of PAH and hospitalization due to PAH. But, it also has some side effects, such as headache, sore throat, and anemia.
Pulmonary arterial hypertension (PAH)
Opsumit (macitentan) is an endothelin receptor antagonist. It works by blocking the effects of a protein in your body called endothelin. Doing so relaxes the blood vessels that go from your heart to your lungs and allows more blood to flow through. This lowers the amount of work your heart needs to pump blood to your lungs to get oxygen for your body. As a result, it's easier for you to exercise and breathe.
Source: DailyMed
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
More common
Decrease in the amount of urine
noisy, rattling breathing
pale skin
swelling of the fingers, hands, feet, or lower legs
troubled breathing with exertion
unusual bleeding or bruising
unusual tiredness or weakness
Less common
Abdominal or stomach pain or tenderness
clay colored stools
dark urine
difficult, burning, or painful urination
frequent urge to urinate
lower back or side pain
muscle aches and pains
difficulty with breathing
tightness in the chest
yellow eyes or skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Works well to slow down the worsening of PAH and make it easier to breathe, exercise, and walk longer distances
Taken by mouth once per day with or without food
Might work better than ambrisentan (Letairis) or bosentan (Tracleer)
Not a cure for PAH
Can cause side effects like headache, fluid buildup in the body, and anemia
Not safe to use during pregnancy
Not recommended for breastfeeding mothers because we don't know if it's safe
Make sure to mark your appointments on your calendar for when you need to see your provider. These appointments are important to discuss how treatment is going for you and make sure Opsumit (macitentan) is safe for you to take. For example, your provider will need to check your liver health regularly and your blood cell counts periodically.
Take Opsumit (macitentan) with or without food at the same time day every day.
Swallow Opsumit (macitentan) tablets whole. Don't split, crush, or chew the tablets. If you're having trouble swallowing the tablets, contact your provider.
Opsumit (macitentan) can cause your body to hold onto too much fluid and swell up. Contact your provider if you notice shortness of breath, unexpected weight gain, or swelling in the ankles or feet.
Opsumit (macitentan) interacts with a lot of medications (prescription and over-the-counter), including amiodarone (Pacerone), diltiazem (Cardizem), and fluconazole (Diflucan), among many others. Make sure to let your provider know about all the medications you're taking (including vitamins and supplements) before starting Opsumit (macitentan) so that they can check for interactions. If there are interactions, your provider might switch you to a different medication to prevent harmful effects.
If you're a woman who's able to have children, it's recommended that you use birth control during treatment with Opsumit (macitentan) and for at least 1 month after your last dose. In addition, you'll need to do a pregnancy test every month while you take Opsumit (macitentan). Let your provider know right away if you get pregnant while taking this medication. Opsumit (macitentan) can potentially harm an unborn baby.
If you're a man and are prescribed Opsumit (macitentan), let your provider know if there's a possibility you might want to have children in the future. This medication might not be the best option for you because Opsumit (macitentan) can lower your sperm count. It's not known if this effect is reversible after you stop the medication.
Opsumit (macitentan) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Opsumit (macitentan) shouldn't be taken during pregnancy. While it hasn't been studied in human pregnancy, animal studies show that it can cause severe and life-threatening harm to unborn babies. Because of this risk, Opsumit (macitentan) is available only through the Opsumit REMS program. If you're a woman who's able to have children, your provider will ask you take a pregnancy test before you start Opsumit (macitentan), monthly during treatment, and once more a month after you stop the medication. Women who are able to get pregnant should use birth control during treatment with Opsumit (macitentan) and for at least 1 month after completing treatment. If you're pregnant or thinking of becoming pregnant, talk to your provider about the risks and benefits of using Opsumit (macitentan) during pregnancy.
Opsumit (macitentan) can cause liver problems that can sometimes lead to liver failure. You'll need to get blood tests to check your liver health before and during treatment. These blood tests make sure your liver is working properly. Get medical attention right away if you notice symptoms of liver problems, such as swelling of your stomach, stomach pain, yellowing of your skin or the whites of your eyes, stool changes (black, tarry, or bloody stools), nausea, vomiting, or dark or brown urine. You might need to stop taking Opsumit (macitentan) to prevent further liver damage.
Risk factors: Heart failure
Opsumit (macitentan) can cause fluid buildup in the body, leading to swelling or shortness of breath. If you have a history of heart failure, this fluid buildup can be severe and worsen your heart condition. Fluid buildup can start to happen within weeks of starting Opsumit (macitentan). If you have any heart problems or heart failure, let your provider know before starting Opsumit (macitentan). Contact your provider if you have any signs of heart failure, like shortness of breath; swelling in the legs, ankles, or feet; irregular heartbeat; not able to exercise; or tiredness while taking Opsumit (macitentan).
Risk factors: Severe anemia
Opsumit (macitentan) might cause your hemoglobin levels to go down. Hemoglobin is the protein on your red blood cells that carries oxygen to the rest of your body. Low hemoglobin levels can lead to anemia. You will need regular blood tests while taking Opsumit (macitentan) to make sure your hemoglobin stays at a healthy level. If you have a history of anemia, speak with your provider before taking Opsumit (macitentan) so they can make sure it's safe for you to take. If you experience weakness, shortness of breath, dizziness, fast or irregular heartbeat, or pale skin while taking Opsumit (macitentan), let your provider know.
The typical dose is 10 mg by mouth once per day.
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Pregnancy
By signing up, I agree to GoodRx's Terms and Privacy Policy, and to receive marketing messages from GoodRx.
Actelion Pharmaceuticals US, Inc. (2023). Opsumit- macitentan tablet, film coated [package insert]. DailyMed.
Actelion Pharmaceuticals US, Inc. (n.d.). Benefits of OPSUMIT®.
American Heart Association. (2023). Pulmonary hypertension - High blood pressure in the heart-to-lung system.
Billett, H. H. (1990). Chapter 151: Hemoglobin and hematocrit. Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edition.
Canadian Agency for Drugs and Technologies in Health. (2015). Drugs for pulmonary arterial hypertension. CADTH Report/Project in Briefs.
Centers for Disease Control and Prevention. (2019). Pulmonary hypertension.
Fagan, K. A., et al. (2001). Role of endothelin-1 in lung disease. Respiratory Research.
Humbert, M., et al. (2022). 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: Developed by the task force for the diagnosis and treatment of pulmonary hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS). Endorsed by the International Society for Heart and Lung Transplantation (ISHLT) and the European Reference Network on rare respiratory diseases (ERN-LUNG). European Heart Journey.
Li, J., et al. (2022). Efficacy and safety of switching from bosentan or ambrisentan to macitentan in pulmonary arterial hypertension: A systematic review and meta-analysis. Frontiers in Cardiovascular Medicine.
Macitentan REMS. (n.d.). A Risk Evaluation and Mitigation Strategy (REMS) is a program required by the Food and Drug Administration (FDA) to manage serious risks associated with a drug product.
MedlinePlus. (n.d.). Hemoglobin test.
U.S. Food and Drug Administration. (2023). Risk evaluation and mitigation strategies | REMS.
Zhang, Y., e tal. (2019). A network meta-analysis for safety of endothelin receptor antagonists in pulmonary arterial hypertension. Cardiovascular Diagnosis & Therapy.
Research prescriptions and over-the-counter medications from A to Z, compare drug prices, and start saving.