Possible Side Effects While Using This Medicine:
Call your doctor right away if you notice any of these side effects:

• Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
• Dark urine or pale stools, nausea, vomiting, loss of appetite, stomach pain, yellow skin or eyes
• Trouble breathing
• Unusual bleeding, bruising, or weakness

If you notice these less serious side effects, talk with your doctor:

• Headache
• Stuffy or runny nose, sore throat

If you notice other side effects that you think are caused by this medicine, tell your doctor.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

When This Medicine Should Not Be Used:
This medicine is not right for everyone. Do not use if you are pregnant or breastfeeding.

How to Use This Medicine:
Tablet

• Your doctor will tell you how much medicine to use. Do not use more than directed.
• Swallow the tablet whole. Do not crush, break, or chew it.
• This medicine should come with a Medication Guide. Ask your pharmacist for a copy if you do not have one.
• Missed dose:Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
• Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

Drugs and Foods to Avoid:
Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

• Some foods and medicines can affect how macitentan works. Tell your doctor if you are using ketoconazole, rifampin, or ritonavir.

Warnings While Using This Medicine:

• It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant. You must use 2 forms of effective birth control to avoid pregnancy while you use this medicine and for at least 1 month after you stop taking the medicine.
• You must have a negative pregnancy test before you start using this medicine and every month during your treatment. Tell your doctor right away if you think you have become pregnant.
• Tell your doctor if you have liver problems or anemia.
• This medicine may cause the following problems:
  
  • Liver problems
  • Anemia
  • Pulmonary edema
• This medicine may affect a man's ability to father a child by decreasing the amount of sperm made. Talk with your doctor before you use this medicine if you plan to have children.
• Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
• Keep all medicine out of the reach of children. Never share your medicine with anyone.