Letairis prevents thickening of the blood vessels, especially those in the lungs and heart. Ambrisentan also lowers blood pressure in your lungs, helping your heart pump blood more efficiently.

Letairis is used to treat pulmonary arterial hypertension (PAH) in adults. It improves your ability to exercise and prevents your condition from getting worse.

Letairis is sometimes used with a medicine called tadalafil (Adcirca).

For women, Letairis is available only from a certified pharmacy under a special program. You must be registered in the program and sign agreements to use birth control and undergo pregnancy and blood testing.

Letairis can harm an unborn baby or cause birth defects. Do not use if you are pregnant. You will need to take a pregnancy test before, during, and after treatment with ambrisentan.

If you are a woman of child-bearing potential, you will be required to use two forms of birth control to prevent pregnancy during your treatment, and for at least 1 month after your treatment ends.

You should not use Letairis if you have idiopathic pulmonary fibrosis.

Before taking this medicine

You should not use Letairis if you are allergic to ambrisentan, or if you have idiopathic pulmonary fibrosis (IPF).

Do not use Letairis if you are pregnant or think you might be pregnant. This medicine can cause serious birth defects. Tell your doctor right away if you miss a menstrual period or think you may have become pregnant.

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 your last dose.

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

Recommended forms of birth control forms include:

• a tubal ligation, or a copper IUD (intrauterine device) or progesterone implant;

• one hormone form (birth control pill, skin patch, implant, vaginal ring, or injection) plus 1 barrier form (condom, diaphragm with spermicide, or cervical cap with spermicide);

• a condom and a female barrier form together (diaphragm with spermicide, or cervical cap with spermicide); or

• a partner's vasectomy plus 1 hormone form or 1 barrier form.

Letairis comes with patient instructions about acceptable forms of birth control to use while taking this medicine. Follow these directions carefully. Ask your doctor about emergency contraception if you have unprotected sex or if you believe your contraception has failed.

To make sure Letairis is safe for you, tell your doctor if you have ever had:

• liver disease; or

• anemia (low red blood cell counts).

You should not breastfeed while you are using ambrisentan.

Ambrisentan may lower a man's sperm count and could affect fertility (your ability to have children).

Letairis is usually taken once daily. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Before you start treatment with Letairis, your doctor may perform blood tests to make sure it is safe for you to take this medicine. Your blood will need to be tested often during treatment.

Letairis can be taken with or without food. Take the medicine at the same time each day.

Do not crush, chew, or split the tablet. Swallow the pill whole.

Store at room temperature away from moisture and heat. Keep this medicine in its original container.

Usual Adult Dose for Pulmonary Hypertension:

Initial dose: 5 mg orally once a day.

Comments:
-Consider increasing the dose to 10 mg orally once a day if 5 mg is tolerated.
-When used with tadalafil, the dose of either drug can be increased as needed and tolerated at 4-week intervals.

Uses:
-For the treatment of pulmonary arterial hypertension (WHO Group 1) to improve exercise ability and delay clinical worsening.
-For the treatment of pulmonary arterial hypertension (WHO Group 1) in combination with tadalafil to reduce the risks of disease progression and hospitalization for worsening pulmonary arterial hypertension, and to improve exercise ability.

You should not use Letairis if you are allergic to ambrisentan, or if you have idiopathic pulmonary fibrosis (IPF).

Do not use Letairis if you are pregnant or think you might be pregnant. This medicine can cause serious birth defects. Tell your doctor right away if you miss a menstrual period or think you may have become pregnant.

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 your last dose.

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

Recommended forms of birth control forms include:

• a tubal ligation, or a copper IUD (intrauterine device) or progesterone implant;

• one hormone form (birth control pill, skin patch, implant, vaginal ring, or injection) plus 1 barrier form (condom, diaphragm with spermicide, or cervical cap with spermicide);

• a condom and a female barrier form together (diaphragm with spermicide, or cervical cap with spermicide); or

• a partner's vasectomy plus 1 hormone form or 1 barrier form.

Letairis comes with patient instructions about acceptable forms of birth control to use while taking this medicine. Follow these directions carefully. Ask your doctor about emergency contraception if you have unprotected sex or if you believe your contraception has failed.

To make sure Letairis is safe for you, tell your doctor if you have ever had:

• liver disease; or

• anemia (low red blood cell counts).

You should not breastfeed while you are using ambrisentan.

Ambrisentan may lower a man's sperm count and could affect fertility (your ability to have children).

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Get emergency medical help if you have signs of an allergic reaction to Letairis: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

• severe shortness of breath, wheezing, cough with foamy mucus, chest pain;

• swelling, tiredness, rapid weight gain;

• low red blood cells (anemia) - pale skin, unusual tiredness, feeling light-headed or short of breath, cold hands and feet; or

• liver problems - loss of appetite, stomach pain (upper right side), nausea, vomiting, fever, itching, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Common Letairis side effects may include:

• swelling in your hands, legs, ankles, or feet;

• stuffy nose, sinus pain; or

• hot flashes, redness in your face.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all your other medicines, especially:

• cyclosporine.

This list is not complete. Other drugs may interact with ambrisentan, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.