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Mechanism of Action

Ambrisentan (Letairis) belongs to a drug class known as endothelin receptor antagonists. It blocks endothelin type A (ETA) receptors, helping relax and widen blood vessels in the lungs.

Endothelin is a protein that constricts blood vessels. In people with PAH, too much endothelin can interfere with blood flow through the lungs, leading to high blood pressure in the lungs.

Important Ambrisentan (Letairis) Information and Warnings

This medication can cause serious birth defects if used during pregnancy. You should not use ambrisentan if you are pregnant. If you can become pregnant, your healthcare provider will check for pregnancy before treatment begins and advise you about pregnancy testing during treatment.

If you can become pregnant, you must use effective birth control during treatment and for at least one month after stopping ambrisentan. Depending on the method, you may need to use two forms of birth control. Ask your healthcare provider which methods are appropriate for you.

Call your healthcare provider immediately if you miss your period or think pregnancy might have occurred.

Don’t take this medication if you:

• Are pregnant or planning to become pregnant
• Have idiopathic pulmonary fibrosis (scarring of the lungs due to no obvious cause)

Ambrisentan may also cause fluid retention and decreased hemoglobin levels, which can lead to anemia. Your healthcare provider may monitor your hemoglobin levels during treatment. Report unusual swelling, rapid weight gain, or worsening shortness of breath promptly.