You should talk with your healthcare provider prior to taking this medication if you have:
- A lung disease known as idiopathic pulmonary fibrosis (scarring of the lungs)
- Kidney disease, such as kidney failure (renal failure)
- Liver disease, such as hepatitis, cirrhosis, or liver failure
- Heart disease, such as heart failure
- Swelling in the arms, hands, legs, ankles, or feet (edema)
- Any allergies, including to foods, dyes, or preservatives.
Also, let your healthcare provider know if you are:
- Pregnant or thinking of becoming pregnant (see Letairis and Pregnancy)
- Breastfeeding (see Letairis and Breastfeeding).
Make sure to tell your healthcare provider about all other medications you are taking, including prescription and nonprescription medicines, vitamins, and herbal supplements.
(Click Precautions and Warnings With Ambrisentan to learn more, including information on who should not take the drug.)
Ambrisentan is an endothelin receptor antagonist. Endothelins are proteins that have a variety of actions in the body, including effects on the heart, blood vessels, lungs, and kidneys. One of the things endothelins do is to cause blood vessels to constrict (narrow). People with PAH have higher-than-normal levels of endothelins in the body.
Endothelin can bind to two receptors. Ambrisentan works by blocking one of those receptors (endothelin A, or ETA receptor), preventing endothelin from binding to the receptor. This helps block the actions of the extra endothelin in people with PAH.