Ambrisentan: what it treats, how to take it, and side effects
Last updated September 7, 2026.
Ambrisentan is a once-daily prescription tablet for pulmonary arterial hypertension, and it belongs to a class of medicines called endothelin receptor antagonists. It blocks endothelin, a natural substance that tightens the small arteries in your lungs, so those vessels relax and your heart works less hard to push blood through them. Over weeks that usually means you can walk farther before you get short of breath. The single most important safety point is pregnancy: ambrisentan can cause serious birth defects, so it is not used during pregnancy and is supplied in the United States only through a restricted program that requires regular pregnancy testing for anyone who can become pregnant.
What does it treat?
Ambrisentan is approved for pulmonary arterial hypertension, meaning WHO Group 1 disease, to improve exercise ability and to delay clinical worsening. That is high blood pressure in the arteries between the heart and lungs, and the pattern people describe is breathlessness with ordinary activity such as stairs or carrying groceries, unusual fatigue, lightheadedness or near-fainting with exertion, and sometimes ankle and leg swelling. It is often prescribed together with tadalafil, which the label supports for reducing the risk of disease progression and hospitalization for worsening PAH; in the United States the two are taken as separate tablets rather than one combination pill. It is not used for pulmonary hypertension caused by idiopathic pulmonary fibrosis, where it is specifically contraindicated, and it does not treat ordinary high blood pressure.
How do you take it?
Ambrisentan comes as 5 mg and 10 mg film-coated tablets taken once a day, with or without food, at about the same time each day. Most people start at 5 mg once daily, and the dose may be raised to 10 mg once daily if it is tolerated; 10 mg once daily is the maximum, and there is no benefit to going higher. Swallow tablets whole, since they should not be split, crushed, or chewed. When ambrisentan is started along with tadalafil, the label sequence is ambrisentan 5 mg plus tadalafil 20 mg once daily, tadalafil raised to 40 mg after 4 weeks, then ambrisentan raised to 10 mg after at least 8 weeks. If you also take cyclosporine, the ambrisentan dose is limited to 5 mg once daily. If you miss a dose, take it when you remember, unless your next dose is close, in which case skip the missed one; never take two doses to catch up. Do not stop on your own, because your lung pressures can rebound, and call your care team promptly if you gain several pounds in a few days, your swelling or breathlessness gets worse, or your skin or the whites of your eyes turn yellow.
Side effects to know
- Common: The effects people notice most often are swelling in the ankles, feet, or legs, nasal and sinus congestion, flushing, headache, palpitations, constipation, and stomach pain, and these are usually mild and steady rather than worsening.
- Serious: Stop and get medical help the same day for rapid weight gain with worsening leg swelling or new breathlessness, which can mean fluid overload or heart failure, and for sudden severe shortness of breath soon after starting, which can point to pulmonary edema from pulmonary veno-occlusive disease. Also get urgent care for yellowing of the skin or eyes, dark urine, pain under the right ribs with nausea and vomiting, or the pale skin, marked fatigue, and breathlessness of a significant drop in hemoglobin.
Who should not take it?
Ambrisentan is contraindicated in pregnancy, in idiopathic pulmonary fibrosis including IPF with pulmonary hypertension, and in anyone who has had a hypersensitivity reaction to it. If you can become pregnant, current FDA labeling requires enrollment in the ambrisentan REMS program, a negative pregnancy test before you start, monthly tests during treatment, and one test one month after you stop, plus two reliable forms of birth control unless you have an IUD or tubal sterilization. Do not breastfeed while taking it, since there is no information on ambrisentan in human milk and the risk to a nursing infant is unknown. Treatment is not recommended if you have moderate or severe liver impairment, and your clinician will usually check liver enzymes before you start and again if symptoms appear. Tell your clinician about cyclosporine, which caps your dose at 5 mg daily, and about rifampin, other PAH drugs, and any diuretics, and know that ambrisentan may lower sperm counts, which matters if you are planning a pregnancy as a partner. There is no direct alcohol interaction, but alcohol adds to liver strain and to lightheadedness, so keep drinking light or skip it and ask your clinician what fits your situation.
When is it an emergency?
Call 911 in the United States if you collapse or faint, cannot catch your breath at rest, cough up pink or frothy sputum, or have chest pain, and for signs of a severe allergic reaction such as swelling of the face, lips, or tongue, hives with trouble breathing, or throat tightness. If you or someone else takes too much ambrisentan, call Poison Control at 1-800-222-1222 right away, even if the person feels fine; large doses have caused headache, flushing, dizziness, nausea, and nasal congestion, and a very large overdose can drop blood pressure enough to cause fainting. If a pregnancy is confirmed or suspected while you are taking ambrisentan, contact your prescriber the same day rather than waiting for your next visit.
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Common questions
What is the maximum dose of ambrisentan?
The ceiling is 10 mg once daily. Most people start at 5 mg once daily and move to 10 mg only if the lower dose is tolerated and their clinician wants more effect. Doses above 10 mg a day are not part of the approved label and do not add benefit. If you take cyclosporine, your dose is capped at 5 mg once daily no matter how well you tolerate it. Never double up to make up for a missed day.
Can I drink alcohol while taking ambrisentan?
There is no direct interaction between alcohol and ambrisentan on the label. The practical issues are that alcohol is processed by the liver, and ambrisentan carries a small risk of liver enzyme changes, so heavy or daily drinking makes those results harder to interpret. Alcohol also widens blood vessels, which can add to flushing and lightheadedness when you stand up. Occasional light drinking is usually workable, but check with the clinician who manages your pulmonary hypertension, especially if your liver tests have ever been abnormal.
Is ambrisentan safe in pregnancy or while breastfeeding?
No. Ambrisentan is contraindicated in pregnancy because it can cause serious birth defects, and this is the reason it is dispensed only through a restricted program in the United States. If you can become pregnant, you need a negative pregnancy test before starting, monthly tests during treatment, and one test one month after your last dose, plus two reliable forms of contraception unless you have an IUD or tubal sterilization. If a pregnancy is confirmed or suspected, contact your prescriber the same day. Breastfeeding is not advised while you take it, since there is no information on whether the drug passes into human milk.
Do I need to take ambrisentan with food?
No. You can take it with or without food, so pick whatever makes it easiest to remember, and keep the timing consistent from day to day. Swallow the tablet whole with water; do not split, crush, or chew it. There are no grapefruit restrictions specific to ambrisentan. If nausea or stomach pain bothers you, taking it with a small meal is reasonable and does not reduce how well it works.
What are the signs of taking too much ambrisentan?
In studies of healthy volunteers, single doses well above the daily maximum caused headache, flushing, dizziness, nausea, and nasal congestion. A much larger overdose can drop blood pressure enough to cause severe lightheadedness or fainting. Call Poison Control at 1-800-222-1222 right away if too much is taken, even without symptoms, and call 911 if the person faints, cannot be roused, or has trouble breathing. Bring the bottle so the tablet strength and count can be checked.
Which medicines and conditions interact with ambrisentan?
Cyclosporine raises ambrisentan levels, so your dose is limited to 5 mg once daily when the two are used together. Rifampin changes ambrisentan exposure and calls for closer monitoring after it is started. Ambrisentan is not recommended if you have moderate or severe liver impairment, and it is contraindicated in idiopathic pulmonary fibrosis, including IPF with pulmonary hypertension. Tell your clinician about every other pulmonary hypertension medicine, diuretics, and any over-the-counter or herbal products, and expect liver enzymes to be checked before you start.