Letairis (ambrisentan)
An approved treatment for Pulmonary Arterial Hypertension.
Drug facts
The same compound appears under different names depending on the context. Here is how to identify Ambrisentan wherever you encounter it, plus the key facts at a glance.
- Generic name
- Ambrisentan
- Brand name
- Letairis
- Development code
- BSF-208075
- Drug class
- Endothelin receptor antagonist
- Manufacturer
- Gilead Sciences
- How it's taken
- Taken as a single oral tablet once daily, either 5mg or 10mg.
A selective endothelin type A receptor blocker for adults with PAH (WHO Group 1).
- Its safety and effectiveness in children have not been established.
- By specifically blocking the ETA receptor while largely sparing ETB, it reduces vessel constriction while potentially preserving some beneficial ETB-mediated effects like nitric oxide release.
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Where Ambrisentan fits
Selective endothelin A receptor antagonist for PAH, part of the standard combination therapy approach. Notable for the AMBITION trial demonstrating benefit of upfront combination therapy.
How Ambrisentan works
Ambrisentan preferentially blocks the ETA receptor, which mediates the vasoconstriction and cell proliferation effects of endothelin-1 in pulmonary arteries. By being selective for ETA over ETB, it may preserve ETB-mediated clearance of endothelin and production of vasodilators like nitric oxide and prostacyclin.
Side effects and safety
Peripheral edema, nasal congestion, sinusitis, and flushing are common. It can lower hemoglobin (anemia), sometimes enough to need a blood transfusion, so hemoglobin is checked before starting, at 1 month, and from time to time after that. The label also warns about fluid buildup that sometimes needs hospital care, sudden fluid in the lungs in people with a rare condition called pulmonary veno-occlusive disease, and lower sperm counts.
It has a boxed warning: it must not be used in pregnancy because it may cause serious birth defects. Pregnancy must be ruled out before starting, and people who can become pregnant must use effective birth control during treatment and for 1 month after stopping. It should not be used by people with idiopathic pulmonary fibrosis. Since April 2025 it is no longer limited to a REMS program, and the label no longer requires monthly pregnancy tests.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Ambrisentan
Taken as a single oral tablet once daily, either 5mg or 10mg. No food restrictions. It is usually started at 5mg, alone or with tadalafil, and can be raised to 10mg at 4-week intervals. Do not split, crush, or chew the tablets. The REMS program that required prescriber and pharmacy certification was removed in April 2025.
Availability and cost
Generic versions may be available at a lower cost. Ask your pharmacist.
Selective endothelin A receptor antagonist for PAH. Generic ambrisentan is available from several manufacturers, and brand Letairis is still sold by Gilead.
Help paying for Letairis
With private insurance, the drugmaker's copay card can lower what you pay for Letairis. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE, but charity funds often can. Of the 4 charity funds for Pulmonary Arterial Hypertension, 2 were open on October 26, 2026. Pick your insurance below to see which offers fit you.
- Copay help
Eligible patients with commercial insurance could pay as little as $5 per month for Letairis. Not available to people enrolled in government prescription drug programs such as Medicare, Medicaid, TRICARE or DoD. Additional restrictions may apply.
For: private insurance · source
Good to know: Sponsor: Gilead. The program covers brand Letairis only; generic ambrisentan is also available. Call 1-866-664-5327, Monday through Friday, 8am to 8pm ET. Gilead's current page does not describe a free-drug program or an annual copay maximum for Letairis, so ask the program line about other help.
Charity funds for Pulmonary Arterial Hypertension
- From a charity · HealthWell FoundationPulmonary Hypertension (Medicare Access) fundOpen
Pays for: Copays, premiums or other treatment costs. Medicare patients only.
- From a charity · TotalAssist (formerly PAN Foundation)Pulmonary Hypertension fundOpen
Pays for: Out-of-pocket costs for approved medications, up to $9,500 per year. Requires health insurance (any kind).
- From a charity · The Assistance FundPulmonary Hypertension fundWaitlist
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
Every program and charity fund for Pulmonary Arterial Hypertension →
Clinical trial results
ARIES-1 and ARIES-2 Phase 3 trials showed improvement in exercise capacity and time to clinical worsening. AMBITION trial demonstrated superiority of initial combination therapy (ambrisentan + tadalafil) over monotherapy.
Development history
Approved by FDA in June 2007. The AMBITION trial (2015) was pivotal in establishing upfront combination therapy as standard of care in PAH. Often used in combination with tadalafil as a first-line oral regimen.
Explore Pulmonary Arterial Hypertension trials
Other Pulmonary Arterial Hypertension treatments
Common questions about Ambrisentan
▸What is Ambrisentan (Letairis)?
A selective endothelin type A receptor blocker for adults with PAH (WHO Group 1). Its safety and effectiveness in children have not been established. By specifically blocking the ETA receptor while largely sparing ETB, it reduces vessel constriction while potentially preserving some beneficial ETB-mediated effects like nitric oxide release.
▸How does Ambrisentan work?
Ambrisentan preferentially blocks the ETA receptor, which mediates the vasoconstriction and cell proliferation effects of endothelin-1 in pulmonary arteries. By being selective for ETA over ETB, it may preserve ETB-mediated clearance of endothelin and production of vasodilators like nitric oxide and prostacyclin.
▸What are the side effects of Ambrisentan?
Peripheral edema, nasal congestion, sinusitis, and flushing are common. It can lower hemoglobin (anemia), sometimes enough to need a blood transfusion, so hemoglobin is checked before starting, at 1 month, and from time to time after that. The label also warns about fluid buildup that sometimes needs hospital care, sudden fluid in the lungs in people with a rare condition called pulmonary veno-occlusive disease, and lower sperm counts. It has a boxed warning: it must not be used in pregnancy because it may cause serious birth defects. Pregnancy must be ruled out before starting, and people who can become pregnant must use effective birth control during treatment and for 1 month after stopping. It should not be used by people with idiopathic pulmonary fibrosis. Since April 2025 it is no longer limited to a REMS program, and the label no longer requires monthly pregnancy tests.
▸How is Ambrisentan taken?
Taken as a single oral tablet once daily, either 5mg or 10mg. No food restrictions. It is usually started at 5mg, alone or with tadalafil, and can be raised to 10mg at 4-week intervals. Do not split, crush, or chew the tablets. The REMS program that required prescriber and pharmacy certification was removed in April 2025.
▸Is Ambrisentan FDA approved?
Yes, Ambrisentan (Letairis) is FDA approved (2007) for the treatment of Pulmonary Arterial Hypertension.
▸What is the AMBITION trial and why is it important?
The AMBITION trial was a landmark PAH study that compared initial upfront combination therapy (ambrisentan plus tadalafil together from the start) to monotherapy with either drug alone. Combination therapy reduced clinical failure events by 50% compared to monotherapy. This trial established upfront combination therapy as the standard of care for PAH, changing how newly diagnosed patients are treated worldwide.
▸How does ambrisentan differ from bosentan and macitentan?
Ambrisentan is a selective ETA receptor antagonist, while bosentan and macitentan block both ETA and ETB receptors. The clinical significance of this selectivity is debated. Practically, ambrisentan does not require the monthly liver testing that bosentan does (lower hepatotoxicity risk), is dosed once daily, and has well-established combination data with tadalafil from the AMBITION trial. Peripheral edema (leg swelling) may be more common with ambrisentan.
▸Why is ambrisentan often paired with tadalafil?
The AMBITION trial specifically tested the combination of ambrisentan and tadalafil and showed superior outcomes compared to either drug alone. This evidence-based pairing has made ambrisentan plus tadalafil one of the most commonly prescribed initial combination regimens for PAH. Other combinations are also used, but the AMBITION data provides the strongest evidence for this specific pair.
▸Is ambrisentan safe during pregnancy?
No. Ambrisentan is teratogenic and can cause serious birth defects. It is contraindicated in pregnancy, and women of reproductive potential must use reliable contraception. A pregnancy test is required before starting. Since April 2025 the label no longer requires monthly tests or the REMS program, so contact your doctor right away if a period is late or you think you might be pregnant. Ambrisentan must be stopped immediately if pregnancy is suspected.