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

Sirolimus (brand name Rapamune) occupies a distinct pharmacological niche in transplant immunosuppression and rare disease management. As an mTOR inhibitor, it offers a mechanistic alternative to calcineurin inhibitors — particularly valuable in patients with calcineurin inhibitor–related nephrotoxicity or in those requiring combination mTOR-plus-CNI minimization regimens. It is also the first and only FDA-approved oral agent for lymphangioleiomyomatosis (LAM).

This article is intended for transplant physicians, nephrologists, pulmonologists, and other specialists who prescribe sirolimus. We provide an up-to-date picture of the supply landscape, clinical considerations for managing patients during access challenges, and resources you can share with your care team.

Supply Status as of 2026

As of early 2026, sirolimus is not listed on the FDA Drug Shortage Staff or ASHP current shortage databases. The market includes multiple generic manufacturers — Zydus, Amneal, Teva, Glenmark, and others — providing a degree of supply redundancy not present when only brand Rapamune was available.

However, sirolimus remains a low-volume specialty medication at most retail pharmacies. Localized and transient stocking failures are common, particularly for:

• The oral solution formulation (1 mg/mL) — refrigeration requirements and shorter stability limit retail stocking
• The 0.5 mg tablet strength — lower demand means less consistent availability compared to 1 mg and 2 mg tablets
• Patients in geographic areas with lower transplant density — pharmacies in these regions may not regularly stock sirolimus

Clinical Considerations When a Patient Cannot Access Sirolimus

When a transplant patient on sirolimus reports inability to fill their prescription, the clinical priority framework should include:

1. Assess Urgency Based on Current Trough Levels

If the patient has recent trough levels in therapeutic range (typically 12–20 ng/mL for stable transplant patients) and has only missed 1–2 doses, the urgency is moderate. If they are already below therapeutic range or have missed 3+ doses, urgent action is required to prevent rejection.

2. Facilitate Pharmacy Access Through Your Transplant Center

Most transplant centers maintain relationships with specialty pharmacies or have hospital pharmacy dispensing capabilities for outpatient emergency use. Engaging your transplant pharmacy coordinator is typically the fastest path to resolution.

3. Consider Pharmacokinetic Bridge Options

In cases of extended unavailability, a carefully managed transition to everolimus (Zortress) — the nearest pharmacological alternative as a fellow mTOR inhibitor — may be appropriate for transplant patients. Key pharmacokinetic considerations:

• Sirolimus and everolimus are not mg-for-mg interchangeable — recalculate dosing based on target trough concentrations
• Everolimus target trough for transplant: 3–8 ng/mL (lower than sirolimus target of 12–20 ng/mL)
• Everolimus has a shorter half-life (~28 hours vs sirolimus ~62 hours), allowing for faster dose adjustments
• Both drugs carry the same class-related risks: infection, hyperlipidemia, thrombocytopenia, and impaired wound healing

4. Considerations for LAM Patients

LAM patients are particularly vulnerable because sirolimus is the only FDA-approved oral therapy for this indication as of 2026. If a LAM patient cannot access sirolimus, you may consider an off-label bridge with everolimus, but document the clinical rationale carefully and inform the patient that this represents off-label use. The LAM Foundation may be able to assist with patient assistance and navigation resources.

Drug Interactions: Key Vigilance Points in the Outpatient Setting

Sirolimus is a substrate of CYP3A4 and P-glycoprotein (P-gp). Concurrent medications that inhibit or induce these pathways can cause clinically significant changes in sirolimus blood levels:

• Strong CYP3A4 inhibitors (voriconazole, ketoconazole, itraconazole): Can dramatically elevate sirolimus levels — coadministration with voriconazole is contraindicated
• Strong CYP3A4 inducers (rifampin, rifapentine, phenytoin, carbamazepine, St. John's Wort): Markedly decrease sirolimus levels, risking sub-therapeutic exposure
• Cyclosporine: Increases sirolimus AUC approximately 2-fold; patients should take sirolimus 4 hours after cyclosporine
• Cannabidiol (CBD): Emerging data suggest CBD may increase sirolimus exposure; dose reduction and additional monitoring should be considered

Therapeutic Drug Monitoring Guidance

All sirolimus prescribing information requires therapeutic drug monitoring (TDM). Clinically relevant benchmarks:

• First year post-transplant target trough: 16–24 ng/mL (with concurrent cyclosporine)
• Post-cyclosporine withdrawal target: 12–20 ng/mL
• LAM target trough: 5–15 ng/mL
• Sirolimus half-life is approximately 62 hours — steady state is reached in approximately 5–7 days; do not adjust dose more frequently than every 7–14 days

How medfinder Can Help Your Patients

When patients call your office unable to find sirolimus, directing them to medfinder can help resolve access issues quickly. medfinder contacts pharmacies near the patient to check sirolimus availability and texts the results — reducing anxiety and saving time for both the patient and your office staff.

Providers can learn more and access provider-specific resources at medfinder.com/providers.

Summary for Clinicians

Sirolimus is not in a formal shortage as of early 2026, but localized access failures remain clinically relevant for your transplant and LAM patients. Key action items: route patients to specialty pharmacies or mail-order, maintain a low threshold for engaging hospital pharmacy channels, and have a documented protocol for bridge therapy with everolimus in cases of extended unavailability. For a provider's guide to helping patients navigate availability, see our

provider's guide to helping patients find sirolimus