Macitentan is used to treat high blood pressure in the lungs (pulmonary arterial hypertension). This condition is thought to be caused by increased levels of a certain natural substance (endothelin-1). This medication blocks the effects of endothelin-1, which helps decrease the blood pressure in the lungs, and reduces the risk of worsening of symptoms and hospital stays due to the disease.

Read the Medication Guide and, if available, the Patient Information Leaflet provided by your pharmacist before you start taking macitentan 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 tablet whole. Do not split, crush, or chew the tablet.

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

Do not increase your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of side effects will increase.

Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets.

Tell your doctor if your condition does not get better or if it gets worse.

Runny nose, sore throat, cough, headache, chills, or body aches may occur. If any of these effects last or get 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.

Tell your doctor right away if you have any serious side effects, including:

• signs of low red blood cell count (such as unusual tiredness, rapid breathing, pale skin, shortness of breath, fast heartbeat)
• unusual weight gain
• new or worsening swelling of the hands/ankles/feet

Macitentan may rarely cause serious liver disease. Tell your doctor right away if you have any symptoms of liver disease, including:

• nausea/vomiting that doesn't stop
• loss of appetite
• dark urine
• stomach/abdominal pain
• yellowing eyes/skin

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 macitentan, 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:

• anemia
• other lung conditions (such as pulmonary veno-occlusive disease)

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

This medication can affect fertility in males. Ask your doctor for more details.

Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets.

This medication must not be used during pregnancy. It may harm an unborn baby. Discuss the use of reliable forms of birth control (such as condoms, birth control pills) during treatment and for 1 month after the last dose. If you become pregnant or think you may be pregnant, tell your doctor right away. See also Warning section.

It is unknown if this medication passes into breast milk. Because of the possible risk to the infant, breastfeeding is not recommended while using this medication. 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.

A product that may interact with this drug is:

• sparsentan

Other medications can affect the removal of macitentan from your body, which may affect how macitentan works. Examples include amiodarone, azole antifungals (such as fluconazole, ketoconazole), cobicistat, macrolide antibiotics (such as clarithromycin), rifamycins (such as rifampin), ritonavir, among others.

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 tests (such as liver function, pregnancy tests, hemoglobin) 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.