What Is Sirolimus? Uses, Dosage, and What You Need to Know in 2026

Sirolimus — also known as rapamycin and sold under the brand name Rapamune — is an immunosuppressant medication prescribed primarily to prevent organ rejection after kidney transplantation and to treat a rare lung disease called lymphangioleiomyomatosis (LAM). It belongs to a drug class called mTOR inhibitors, which work by a fundamentally different mechanism than the most commonly used transplant drugs.

Originally discovered from a soil bacterium found on Easter Island (Rapa Nui) — which is how the name "rapamycin" came about — sirolimus has become a cornerstone of transplant medicine since its FDA approval in 1999. In 2026, it remains one of the most important immunosuppressants available, with growing interest in its potential beyond transplantation.

What Is Sirolimus Used For?

Sirolimus has three FDA-approved uses as of 2026:

1. Prevention of kidney transplant rejection: Sirolimus (as Rapamune) is approved to prevent organ rejection in kidney transplant patients aged 13 and older. It's typically used in combination with cyclosporine and corticosteroids in the initial post-transplant period.
2. Lymphangioleiomyomatosis (LAM): FDA approved in May 2015, sirolimus became the first and only approved oral therapy for this rare, progressive lung disease that primarily affects women of childbearing age.
3. Perivascular epithelioid cell tumors (PEComa): Nab-sirolimus (Fyarro), a different formulation, is FDA-approved for advanced malignant PEComa.

Sirolimus is also used off-label for tuberous sclerosis complex (TSC), certain autoimmune conditions, and is being actively researched for anti-aging applications given its effect on the mTOR pathway that controls cellular aging.

What Forms Does Sirolimus Come In?

Sirolimus is available in the following formulations:

• Oral tablets: 0.5 mg, 1 mg, and 2 mg triangular-shaped tablets
• Oral solution: 1 mg/mL liquid (must be stored in refrigerator; can be kept at room temperature up to 15 days)
• Topical gel (Hyftor): 0.2% sirolimus gel, approved in the EU for facial angiofibromas in tuberous sclerosis; approved in the U.S. in 2022
• Nab-sirolimus (Fyarro): Protein-bound particles for IV infusion, FDA-approved for malignant PEComa

How Is Sirolimus Dosed?

Dosing depends on your specific situation and is guided by blood level monitoring (called therapeutic drug monitoring or TDM). General dosing patterns include:

• Kidney transplant (standard risk): 6 mg loading dose on Day 1, then 2 mg once daily. Target trough: 16–24 ng/mL in first year; 12–20 ng/mL thereafter.
• LAM: Start at 2 mg/day; adjust based on trough levels to achieve 5–15 ng/mL.

Because sirolimus has a long half-life of approximately 62 hours, it takes 5–7 days to reach a new steady state after a dose change. Your doctor should not adjust your dose more frequently than every 7–14 days.

How Should Sirolimus Be Taken?

Key administration instructions:

• Take consistently: Always take with food OR always without food — choose one and stick with it. Food significantly affects how sirolimus is absorbed.
• Avoid grapefruit and grapefruit juice: Grapefruit inhibits the enzyme that breaks down sirolimus, which can raise blood levels to dangerous concentrations.
• Don't crush or chew tablets: Swallow them whole.
• If you use cyclosporine: Take sirolimus 4 hours after cyclosporine, since cyclosporine significantly increases sirolimus blood levels.
• Miss a dose? Take it as soon as you remember: But if it's almost time for your next dose, skip the missed dose — don't double up. Always call your transplant team if you miss multiple doses.

What Makes Sirolimus Different from Tacrolimus?

This is a common question for transplant patients. The key differences:

• Mechanism: Tacrolimus inhibits calcineurin; sirolimus inhibits mTOR — different targets in the immune activation chain
• Kidney toxicity: Sirolimus is less nephrotoxic — it's often chosen for patients with tacrolimus-related kidney damage
• Lipids: Sirolimus causes more hyperlipidemia (high cholesterol/triglycerides) than tacrolimus
• Diabetes risk: Sirolimus does not commonly cause new-onset diabetes (post-transplant diabetes), which is a known risk with tacrolimus
• Wound healing: Sirolimus impairs wound healing more significantly than tacrolimus, which is why many centers delay its use until weeks after surgery

How to Get Sirolimus Filled

Sirolimus is a specialty medication not always stocked at every retail pharmacy. Use medfinder to find which pharmacies near you have it in stock, and consider asking your transplant center about specialty pharmacy options for more reliable access.

To learn about lowering the cost of sirolimus, see our guide on

how to save money on sirolimus in 2026