Ambrisentan Shortage: What Providers and Prescribers Need to Know in 2026

If your patients on ambrisentan (Letairis) are calling the office because they cannot fill their prescriptions, this briefing is for you. Ambrisentan is a cornerstone therapy for WHO Group 1 pulmonary arterial hypertension (PAH), and supply disruptions — even manufacturer-specific ones — create real clinical risk for this patient population. Here is what you need to know about the current supply landscape, clinical implications, and practical strategies to ensure your patients maintain uninterrupted treatment.

Supply Landscape: Where Things Stand in 2026

In May 2024, ASHP listed ambrisentan tablets (Zydus) in shortage. The bulletin was updated in December 2024 as Zydus reported returning product availability. As of early 2026, the following manufacturers have ambrisentan supply:

Generic: Apotex (5 mg and 10 mg, 30-count), Cipla USA, Mylan, Sun Pharma, Teva, Zydus

Brand Letairis: Gilead Sciences (5 mg and 10 mg, 10- and 30-count bottles) via LEAP-certified specialty pharmacies

The multi-manufacturer generic landscape is the most important development for long-term supply stability. However, individual pharmacy stocking varies because different wholesalers source from different manufacturers. A patient presenting with an access problem may be experiencing a pharmacy-specific or manufacturer-specific issue rather than a market-wide shortage.

Clinical Implications of Treatment Interruption

Ambrisentan works by selectively blocking the ETA endothelin receptor, reducing pulmonary vasoconstriction and vascular remodeling. Abrupt discontinuation removes this benefit and can lead to:

Rapid increase in pulmonary vascular resistance

Increased right ventricular afterload and potential right heart decompensation

Worsening dyspnea, decreased exercise tolerance, and reduced functional class

For patients on ambrisentan plus tadalafil combination therapy, loss of ERA coverage may also destabilize the optimized hemodynamic state achieved per the AMBITION trial protocol

For patients with WHO functional class III or IV disease, treatment gaps may be especially dangerous. Counsel patients explicitly not to discontinue ambrisentan without your guidance, even if they are struggling to fill their prescription.

Prescribing Strategies to Minimize Access Risk

Prescribe generic ambrisentan by default. Generic ambrisentan is available at retail pharmacies as well as specialty pharmacies, significantly broadening access options. Brand Letairis remains restricted to specialty pharmacy networks.

Establish preferred specialty pharmacy relationships. Identify two or three specialty pharmacies that reliably stock ambrisentan and maintain them as preferred referral options for your patients.

Maintain a small sample supply. Work with Gilead's LEAP program representative to ensure you have bridge samples available for patients who experience access delays.

Advise patients to refill early. Counsel patients at every visit to request their refill 10 to 14 days before running out, especially if they have experienced supply problems before.

Proactively manage prior authorizations. Specialty PA approvals can expire without notice. Ensure your office tracks renewal dates and submits documentation promptly to prevent coverage lapses.

When to Consider Therapeutic Substitution

Therapeutic substitution from ambrisentan to an alternative ERA (bosentan or macitentan) should only be considered after all access options have been exhausted. Both bosentan and macitentan are FDA-approved for WHO Group 1 PAH and work through a similar endothelin antagonist mechanism, but each carries different monitoring requirements, drug interaction profiles, and cost implications.

If a switch is necessary, document the clinical rationale thoroughly, assess hemodynamics if feasible, and plan for close clinical monitoring during the transition period. For patients on ambrisentan plus tadalafil (per AMBITION data), determine whether the ERA switch is sufficient or whether the entire regimen requires re-evaluation.

Patient Access Resources to Know

LEAP (Letairis Education and Access Program): 1-866-664-5327 — Gilead's program for brand Letairis patients, offering copay assistance for commercially insured patients and patient assistance for qualifying uninsured patients

Zydus Copay Savings Program: Eligible commercially insured patients on generic ambrisentan may pay as little as $0 per prescription

ASHP Drug Shortage Database: ashp.org — check for the most current ambrisentan shortage status and manufacturer availability updates

medfinder for providers: Visit medfinder.com/providers to learn how medfinder can help your patients locate ambrisentan at pharmacies near them, saving both the patient and your office time and frustration.

Key Takeaway for Your Practice

Ambrisentan supply is stable in 2026 but localized access challenges remain. Proactive patient counseling, early refill practices, established specialty pharmacy relationships, and available patient support programs are your best tools for ensuring uninterrupted therapy. See our companion guide on how to help your patients find ambrisentan in stock for step-by-step provider guidance.