What is Opsumit?

Do not administer macitentan to a pregnant female because it may cause fetal harm. Exclude pregnancy before treatment initiation, monthly during treatment, and one month after treatment discontinuation in females of reproductive potential. Use acceptable contraception to prevent pregnancy during treatment and for one month after stopping treatment. Macitentan is only available for female patients through a restricted program under a Risk Evaluation and Mitigation Strategy (REMS) .

Macitentan treats symptoms of pulmonary arterial hypertension, which is high blood pressure in the main artery that carries blood from the right side of the heart (the ventricle) to the lungs. When the small blood vessels in the lungs become more resistant to blood flow, the right ventricle must work harder to pump enough blood through the lungs. Macitentan works by relaxing these blood vessels and increasing the supply of blood to the lungs, which reduces the workload of the heart.

This medicine is available only with your doctor's prescription.

Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. Also, do not stop taking this medicine without checking with your doctor first.

It is very important that you understand the rules of the Opsumit® REMS program. Read the patient Medication Guide. Ask your doctor or pharmacist if you have any questions. You might be asked to sign a form to show that you understand the information.

Swallow the tablet whole. Do not crush, break, or chew it.

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

• For oral dosage form (tablets):
  • For pulmonary arterial hypertension:
    • Adults—10 milligrams (mg) once a day.
    • Children—Use and dose must be determined by your doctor.

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Appropriate studies have not been performed on the relationship of age to the effects of macitentan in the pediatric population. Safety and efficacy have not been established.

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of macitentan in the elderly.

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

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.

• Atazanavir
• Boceprevir
• Carbamazepine
• Clarithromycin
• Cobicistat
• Conivaptan
• Enzalutamide
• Fluconazole
• Fosphenytoin
• Idelalisib
• Indinavir
• Itraconazole
• Ketoconazole
• Lopinavir
• Nefazodone
• Nelfinavir
• Phenytoin
• Posaconazole
• Primidone
• Rifabutin
• Rifampin
• Rifapentine
• Ritonavir
• Saquinavir
• St John's Wort
• Telaprevir
• Telithromycin
• Tipranavir
• Voriconazole

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Anemia (low red blood cells), severe or
• Fluid retention (edema) or
• Heart disease or
• Liver disease—Use with caution. May make these conditions worse.

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly and to check for unwanted effects. Blood tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can cause very serious birth defects. Use 2 forms of effective birth control to keep from getting pregnant while you are using this medicine (even if the medicine is temporarily stopped), and for at least 1 month after you stop taking the medicine. The most effective forms of birth control are hormone birth control pills, patches, shots, vaginal rings, or implants, or a vasectomy (for men). One of these forms of birth control should be combined with a condom, a diaphragm, or a cervical cap. If a woman has had a tubal ligation or has an IUD, she does not need to use a second form of birth control. If you think you have become pregnant while using this medicine, tell your doctor right away.

If you are a woman who can get pregnant, you must have a negative pregnancy test before you will be allowed to take this medicine. You will also be required to have a pregnancy test every month during your treatment. If you miss a period while you are using this medicine, tell your doctor right away.

Check with your doctor right away if you start to have nausea, vomiting, fever, dark-colored urine or pale stools, a loss of appetite, pain in your upper stomach, or yellow eyes or skin. These could be signs of liver injury.

This medicine may cause fluid retention in some patients. Tell your doctor right away if you have bloating or swelling of the face, arms, hands, lower legs, or feet, or rapid weight gain after using this medicine.

Pulmonary edema may occur with this medicine. Check with your doctor right away if you have chest pain, difficult, fast, or noisy breathing, blue lips and fingernails, pale skin, increased sweating, coughing that sometimes produces a pink frothy sputum, or trouble breathing.

This medicine may decrease the amount of sperm men make and affect their ability to have children. If you plan to have children, talk with your doctor before using this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.