Mirabegron XR Shortage: What Providers and Prescribers Need to Know in 2026

Mirabegron extended-release (Myrbetriq) has become a first-line pharmacologic option for overactive bladder (OAB) — particularly for patients who cannot tolerate the anticholinergic side effect burden of older agents. In 2026, clinicians are encountering new barriers to patient access that require proactive management. This briefing summarizes the current situation and provides clinical guidance for urologists, urogynecologists, primary care physicians, and other prescribers.

Current Access Landscape for Mirabegron XR in 2026

Brand-name Myrbetriq (Astellas Pharma) is not listed on the FDA's official drug shortage database and remains generally available through major pharmacy chains. However, two distinct supply- and coverage-related challenges are affecting patient access:

Challenge 1: Generic Supply Disruption from Patent Litigation

In September 2022, Lupin Pharmaceuticals received the first generic approval for mirabegron extended-release tablets following patent expiration. Multiple additional manufacturers — Zydus, Alkem, Aurobindo, Sawai USA — subsequently received approvals, creating a competitive generic market.

In April 2025, however, a federal court issued a preliminary injunction blocking Lupin and Zydus from marketing their generic versions, citing ongoing patent infringement claims by Astellas. This effectively removed two major market participants. The remaining manufacturers — primarily Alkem — continue to supply, but pharmacy-level inventory is inconsistent as the supply chain adjusts.

The clinical implication: patients who were successfully stabilized on generic mirabegron at lower cost may face out-of-pocket price increases or supply gaps. Prescribers should anticipate calls from patients or pharmacy staff and have contingency plans ready.

Challenge 2: UnitedHealthcare Step Therapy Policy (Effective November 2025)

Effective November 2025, UnitedHealthcare and affiliated plans implemented step therapy requirements for mirabegron on commercial formularies. Under this policy, patients are required to first attempt and demonstrate clinical failure with two alternative OAB agents (typically first-line antimuscarinics such as oxybutynin or tolterodine) before Mirabegron XR will be covered.

This represents a significant shift for practices with high UnitedHealthcare patient volume. Importantly, patients who were already established on Mirabegron XR prior to November 2025 may be grandfathered in on some plans, but those enrolled in new plans at open enrollment (effective January 2026) may be subject to the new policy.

Clinical Populations Most Vulnerable to These Access Barriers

Geriatric patients: Mirabegron is frequently prescribed in older adults specifically to avoid anticholinergic burden — the same drugs step therapy now requires them to try first. Mandatory anticholinergic trials in elderly patients may increase fall risk, urinary retention, confusion, and constipation.

Patients with cognitive impairment or dementia risk: Anticholinergic medications are associated with increased cognitive impairment risk. Requiring trial of these agents in at-risk patients is clinically concerning.

Patients on narrow therapeutic index CYP2D6 substrates: Mirabegron is a moderate CYP2D6 inhibitor. While this requires monitoring, patients on flecainide, metoprolol, or tricyclic antidepressants may have their existing medication management complicated if forced to switch agents.

Patients who previously failed or had contraindications to antimuscarinics: This is the strongest clinical basis for a prior authorization exception.

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Prior Authorization Strategy: Building the Medical Necessity Case

For patients who clinically require Mirabegron XR without completing step therapy, a prior authorization (PA) exception should be submitted promptly. Document the following to support the exception request:

Documented history of adverse effects from anticholinergic OAB agents (dry mouth, constipation, urinary retention, confusion) or formal contraindication.

Patient age and cognitive status — document Beers Criteria concerns for elderly patients. Anticholinergics are listed on the AGS Beers Criteria as potentially inappropriate in older adults.

Bladder outlet obstruction or concurrent antimuscarinic use — per prescribing information, mirabegron is safer than antimuscarinics in patients at risk for urinary retention due to BOO.

Clinical stability — for patients already established and responding to Mirabegron XR, document the clinical risk of therapeutic discontinuation.

Therapeutic Alternatives When Mirabegron XR Cannot Be Accessed

When access to Mirabegron XR cannot be secured, consider the following alternatives:

Vibegron (Gemtesa) 75 mg daily: Same mechanism of action (beta-3 agonist), generally available. Notable advantage over mirabegron: vibegron does not inhibit CYP2D6, reducing drug interaction risk. Consider for patients on narrow therapeutic index CYP2D6 substrates.

Solifenacin (Vesicare) 5-10 mg daily: Relatively M3-selective antimuscarinic; generic available; reasonable tolerability profile. Appropriate for patients without significant cognitive or BOO concerns.

Combination therapy (mirabegron + solifenacin): FDA-approved combination for OAB in adults. If mirabegron can be sourced at any dose, combining with low-dose solifenacin may improve efficacy vs. either agent alone.

OnabotulinumtoxinA (Botox) bladder injection: FDA-approved for refractory OAB; highly effective for patients failing pharmacotherapy. Requires office procedure; may be appropriate for patients with persistent inadequate response.

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Savings Resources to Share with Patients

Astellas Momentum Savings Card: Reduces brand Myrbetriq cost for commercially insured patients; available at myrbetriq.com.

Astellas Patient Assistance Program: For uninsured or underinsured income-qualified patients.

GoodRx: Generic mirabegron as low as ~$121/month when in stock.

medfinder: Paid service that locates pharmacies near the patient with Mirabegron XR in stock. Useful for patients facing supply gaps — helps avoid unsuccessful pharmacy runs.

Summary and Recommended Actions for Prescribers

Proactively screen your Mirabegron XR patient panel for those with UnitedHealthcare or affiliated plans who may face new step therapy barriers.

Build templated PA documentation for elderly patients and those with documented antimuscarinic intolerance.

Consider vibegron as a same-class alternative that does not carry the CYP2D6 interaction risk.

Direct patients to medfinder and savings programs to resolve supply and cost barriers.

For a provider-focused guide on helping your patients locate Mirabegron XR, visit medfinder for providers.