Last Updated July 2007
What is ambrisentan?
Ambrisentan is an oral medication used to treat pulmonary arterial hypertension (PAH). It was approved by the Food and Drug Administration (FDA) in 2007 for the treatment of pulmonary arterial hypertension in patients with New York Heart Association (NYHA) Class II or III symptoms. Ambrisentan is part of a class of medication called endothelin receptor antagonists or ERAs.
How does ambrisentan work?
Ambrisentan works by blocking the effects of a substance called endothelin, which is made by the body in increased amounts in patients with PAH. Endothelin causes blood vessels to narrow (constrict). It also causes overgrowth of the muscle in the walls of the blood vessels in the lungs. By blocking the action of endothelin, ambrisentan can reduce blood pressure in the lungs and improve activity level and well being in PAH patients. Studies demonstrate that ambrisentan improves the exercise capacity and delays clinical worsening in PAH patients; long-term trials of the drug showed sustained benefit in exercise capacity.
How is ambrisentan given?
Ambrisentan is taken orally. The initial dose for most patients is 5-mg once daily. If there are no problems or side effects after one month, the dose is increased to 10 mg once daily. Both doses are FDA approved.
What are the frequent side effects of ambrisentan?
Ambrisentan is generally well tolerated by patients with minimal side effects. Side effects and precautions taking this medication are typical of other ERA’s.
The most frequent side effects of ambrisentan were swelling of the lower extremities, nasal congestion, sinusitis, flushing, palpitations, abdominal pain and constipation.
The red blood cell count or hematocrit may decrease in some patients but is rarely important.
Ambrisentan can interact with Cyclosporine A, a medication given to prevent transplant rejection, anti-fungal medications such as ketoconazole, and acid-reflux medications.
The major potential side effect of ambrisentan is damage to the liver. The development of abnormal liver function tests (LFTs), measured in blood samples to greater than three times the upper limit of normal is observed in about 3% of patients receiving this medication.
Ambrisentan has been shown to be harmful to the growing fetus in rats. Therefore, pregnancy should be avoided in women treated with ambrisentan. There is also concern that ambrisentan can effect the development of human sperm.
It is not known whether ambrisentan is excreted in human milk, though studies show that it is passed through breastfeeding in rats. Therefore, nursing mothers should not take ambrisentan.
Monitoring for side effects of ambrisentan:
Because of the potential for damage to the liver, liver function tests must be obtained on a monthly basis as long as a patient is receiving ambrisentan.
Because of the potential harm to the fetus, women of childbearing potential must also have a monthly pregnancy test.
Hematocrit (blood count) should be monitored once a month.
How do patients obtain ambrisentan?
Ambrisentan must be prescribed by a physician. Ambrisentan is sent directly to patients by any of the following specialty pharmacies: Accredo Health Inc., Aetna Specialty Pharmacy, Caremark, CIGNA Tel-Drug, CuraScript, Fairview, Pharm Care Specialty Pharmacy, Walgreens Specialty Pharmacy (Medmark), PrecisionRX Specialty Solutions. Ambrisentan can only be obtained through the Letairis Education and Access Program (LEAP).
Will insurance pay for ambrisentan?
The cost of ambrisentan is about $48,000 per year.
It is expected that most insurance will pay for ambrisentan prescriptions; however, insurance plans with a set co-payment may result in substantial cost to the patient.
Medicaid and most state-run insurance plans will pay for ambrisentan. Gilead Solutions offers a variety of options to cover the cost of the co-payment for the patient.
Do not take ambrisentan if:
- You are pregnant, plan to become pregnant, or become pregnant during treatment with ambrisentan. Notify your treating physician immediately if you become pregnant while receiving ambrisentan.
- Your blood test shows possible liver injury before starting therapy.
- You are taking cyclosporine-A, glyburide or ketaconazole.
Could a patient be allergic to ambrisentan?
This is possible, although there are no reports of this yet.
Pregnant and nursing women
Use of ambrisentan is contraindicated in pregnancy. If a patient becomes pregnant while taking ambrisentan, she should immediately notify the prescribing physician. It is not known whether ambrisentan passes into breast milk.
Use in children
The safety and effectiveness of ambrisentan has not been studied in children.
