Opsumit (Macitentan) – Side Effects, Interactions, Uses, Dosage, Warnings

You should not use macitentan if you are allergic to it.

Tell your doctor if you have ever had:

• liver disease;
• heart disease; or
• anemia (low red blood cells).

This medicine can harm an unborn baby or cause birth defects. Do not use macitentan if you are pregnant or think you might be pregnant. Tell your doctor right away if you miss a menstrual period or think you may have become pregnant during treatment.

You will need to have a negative pregnancy test before starting this treatment. You will be re-tested every month during your treatment, and 1 month after you stop taking this medicine.

Even if you are not planning a pregnancy, you are considered able to become pregnant if:

• you have entered puberty (even if you have not yet started having periods);
• you have never had a hysterectomy or had your ovaries removed; or
• you have not gone through menopause (you have never gone 12 months in a row without a menstrual period).

While taking macitentan and for 30 days after your last dose, you must use a highly effective form of birth control, or two methods together.

• A tubal ligation alone is an effective birth control method.
• An intrauterine device (IUD) or birth control implant alone are also effective birth control methods.
• If you use birth control pills, injections, skin patches, or vaginal rings, you must use a back-up barrier form of birth control, such as a condom or diaphragm or cervical cap. Always use a spermicide gel or insert together with a barrier form of birth control.
• If you use only a barrier method, you must use a second barrier method as a back-up. For example, use a diaphragm or cervical cap in addition to a condom, plus a spermicide gel or insert.
• If your sexual partner has had a vasectomy, you must still use a second method of birth control–either a barrier method or a hormonal form (birth control pills, injections, skin patch, or vaginal ring).

Macitentan comes with patient instructions about acceptable forms of birth control to use while taking this medicine. Follow these directions carefully. Ask your doctor or pharmacist if you have any questions.

If you are the parent or caregiver of a female child taking this medicine, talk to the child's doctor once you notice any signs of puberty (breast development or pubic hair), even if menstrual periods have not yet begun.

Macitentan can decrease sperm count and may affect fertility in men (your ability to have children).

You should not breast-feed while using this medicine.