Alternatives to Ambrisentan (Letairis) If You Can't Fill Your Prescription

Important: Never switch PAH medications on your own. Always work with your pulmonologist or PAH specialist before making any changes. Pulmonary arterial hypertension is a serious, progressive condition and medication changes require careful clinical oversight. If your issue is finding ambrisentan in stock, exhaust all options to locate it before considering a switch.

If you have already exhausted options to fill your prescription, see our guide on how to find ambrisentan in stock near you. If your doctor has determined a therapeutic alternative is appropriate, here is what you need to know about other PAH medications.

Why PAH Medication Switching Is Complex

PAH is treated with medications from several different drug classes that target distinct pathways involved in pulmonary vascular remodeling. Ambrisentan blocks the endothelin-A (ETA) receptor, which reduces vasoconstriction in the lung's blood vessels. Alternatives may work through different mechanisms, have different side effect profiles, require different monitoring, or come with their own access challenges.

The goal of PAH treatment is to keep disease stable and slow progression. Interruptions in therapy — even brief ones — can lead to hemodynamic deterioration. This is why finding ambrisentan itself should always be the first priority, and alternatives are a last resort when supply is truly unavailable.

Alternative 1: Bosentan (Tracleer) — Dual Endothelin Receptor Antagonist

Bosentan (brand name Tracleer) is another endothelin receptor antagonist, but unlike ambrisentan, it blocks both ETA and ETB receptors. It is FDA-approved for PAH (WHO Group 1) in adults and children aged 3 and older. Generic bosentan is available and typically costs $1,500 to $3,000 per month — less than generic ambrisentan.

Key considerations for bosentan:

Requires monthly liver function tests (more liver monitoring than ambrisentan)

Twice-daily dosing (ambrisentan is once daily)

Significant drug interactions, including with cyclosporine, rifampin, and some HIV medications

Also carries pregnancy REMS requirements (teratogenic class effect)

Alternative 2: Macitentan (Opsumit) — Newer Endothelin Receptor Antagonist

Macitentan (brand name Opsumit) is the newest ERA on the market, approved by the FDA in 2013. The SERAPHIN trial demonstrated that macitentan significantly reduced morbidity and mortality in PAH patients. It has a once-daily dosing schedule and is considered to have fewer side effects leading to discontinuation compared to older ERAs.

Key considerations for macitentan:

No routine liver monitoring required (unlike bosentan)

Also has REMS requirements due to teratogenicity

Available combined with tadalafil as Opsynvi — reducing pill burden for patients on dual therapy

No generic available as of 2026 — high cost (specialty pricing)

Alternative 3: Tadalafil (Adcirca) — PDE5 Inhibitor

Tadalafil (Adcirca) is a phosphodiesterase type 5 (PDE5) inhibitor that works by increasing nitric oxide levels in pulmonary vessels, promoting vasodilation. It is FDA-approved for PAH and is commonly prescribed in combination with ambrisentan (the AMBITION trial showed this combination reduced clinical failure by 50% compared to monotherapy).

Key considerations:

Once-daily dosing at 40 mg

Cannot be combined with riociguat (Adempas) — serious hypotension risk

Different mechanism than ambrisentan — may be added to ERA therapy rather than replacing it

Alternative 4: Riociguat (Adempas) — sGC Stimulator

Riociguat (brand name Adempas) is a soluble guanylate cyclase (sGC) stimulator, the only drug of its class. It is FDA-approved for PAH and also for chronic thromboembolic pulmonary hypertension (CTEPH). Riociguat works through a completely different mechanism than ambrisentan.

Important: riociguat cannot be used with PDE5 inhibitors (sildenafil or tadalafil) and also has a REMS program due to teratogenicity. Brand Adempas costs approximately $14,000 to $15,000 per month, and generic riociguat was approved by the FDA but was not commercially available as of early 2026.

Alternative 5: Sildenafil (Revatio) — PDE5 Inhibitor

Sildenafil (brand name Revatio, also used as Viagra) is a PDE5 inhibitor prescribed three times daily for PAH at 20 mg per dose. Generic sildenafil is among the most affordable PAH medications. It is often used in combination with an ERA rather than as a standalone replacement for ambrisentan.

What to Do While Waiting for a Decision

If you cannot fill ambrisentan and are waiting for a clinical decision, do not stop therapy without talking to your doctor first. In the meantime, use medfinder to continue searching for available supply at pharmacies near you. Ask your specialist if they have bridge samples and whether any emergency access programs apply to your situation.