Sirolimus Rx vs rapamycin vs everolimus: what's different

Last updated 2026-07-27

Are sirolimus and rapamycin the same drug?

Yes, completely. Sirolimus is the generic drug name; rapamycin is the original name given to the compound when it was isolated from Streptomyces hygroscopicus, a bacterium found in soil on Easter Island (Rapa Nui, which is where the name comes from) in the 1970s ^[1]. There is no chemical difference. If a compounding pharmacy or telehealth provider sends you "rapamycin," you are getting sirolimus, full stop. The FDA-approved brand name is Rapamune, approved in 1999 to prevent organ rejection in kidney transplant patients ^[2]. Sirolimus also shows up under the brand names Fyarro (an albumin-bound injectable formulation for a rare soft-tissue cancer) and Hyftor (a topical gel for facial angiofibromas in tuberous sclerosis) ^[3]. None of these approvals cover aging, longevity, or lifespan extension. Every use for longevity purposes is off-label, meaning a doctor is prescribing an approved drug for a purpose the FDA never reviewed or cleared. So when people search "sirolimus vs rapamycin," the honest answer is: there's nothing to compare. It's one molecule with two names, the way acetaminophen and Tylenol are the same thing under different labels. The real comparison worth making is sirolimus versus everolimus, which are different molecules in the same drug class.

What is everolimus and how is it different from sirolimus?

Everolimus is a synthetic derivative of sirolimus, chemically modified to change how the body processes it. It was developed by Novartis and approved by the FDA in 2009 as Afinitor for advanced kidney cancer, and it has since picked up approvals for certain breast cancers, pancreatic neuroendocrine tumors, tuberous sclerosis complex, and (as Zortress) transplant rejection prevention ^[3]. The structural change is small (a 2-hydroxyethyl chain added to the sirolimus backbone) but it changes the drug's behavior meaningfully. Everolimus has a much shorter half-life, roughly 30 hours compared to sirolimus's 57 to 62 hours ^{[4] [4]}. That means everolimus clears the body faster and needs more frequent dosing to keep blood levels steady, while sirolimus can be dosed less often because it lingers longer. Everolimus also has somewhat better oral bioavailability and, in some studies, a different side effect emphasis, with mouth sores and metabolic changes reported in both drugs but at different rates depending on dose and population. Both drugs hit the same target (mTORC1), which is why they get lumped together as "rapalogs," but they are not interchangeable prescriptions, and dosing for one doesn't translate directly to the other.

Do sirolimus and everolimus work the same way in the body?

Both drugs bind to a protein called FKBP12, and that complex then inhibits mTORC1 (mechanistic target of rapamycin complex 1), a central regulator of cell growth, protein synthesis, and metabolism ^[1]. This is the mechanism researchers believe underlies the lifespan effects seen in animal studies: less mTORC1 signaling seems to shift cells toward maintenance and repair processes rather than pure growth, echoing what's seen with caloric restriction. The difference is potency and selectivity. Sirolimus is a more complete inhibitor of mTORC1 and, at higher exposure, also affects mTORC2 (which is linked to some of the metabolic side effects like insulin resistance). Everolimus tends to be somewhat less potent at the same milligram dose but is engineered for more predictable pharmacokinetics, which is part of why it's used in transplant regimens where tight drug-level monitoring matters. For the longevity conversation specifically, sirolimus is what's been studied. The NIA Interventions Testing Program, the multi-site standardized aging study run across three universities, has tested sirolimus (encapsulated in food) in genetically diverse mice repeatedly since 2006, not everolimus ^[5]. That's a real gap: almost all of the animal longevity evidence people cite is sirolimus-specific. Everolimus hasn't been through the same testing pipeline for lifespan, so borrowing sirolimus's mouse data to justify everolimus use is a bigger leap than most people realize.

What does the NIA Interventions Testing Program actually show?

The ITP found that sirolimus extended median lifespan in genetically heterogeneous mice, with effects seen even when dosing started late in life. In one widely cited result, mice started on sirolimus at 600 ppm in food at 20 months of age (roughly equivalent to a 60-year-old human) still saw median lifespan increase by 9% in males and 14% in females compared to controls ^[6]. Earlier ITP results, published in Nature in 2009, were the first to show a pharmacological intervention extending lifespan in normal, genetically heterogeneous mice starting treatment as late as 600 days of age . That was a genuinely surprising finding at the time, because most longevity interventions that work in mice only work if started young. These are real, replicated, peer-reviewed results. But they are mouse data. The ITP itself is explicit that these are standardized preclinical trials meant to identify candidates worth testing further, not proof of human benefit. No completed randomized controlled trial has measured whether sirolimus or everolimus extends human lifespan or healthspan, and given that a rigorous human lifespan trial would need to track thousands of people for decades, it's unlikely one will exist anytime soon. Anyone telling you the human evidence for longevity is settled is skipping this part.

Is there any human data on rapamycin and aging at all?

Some, but it's indirect and short-term, not lifespan data. The most cited human study is a 2014 trial from Novartis researchers (Mannick et al., published in Science Translational Medicine) testing an mTOR inhibitor (RAD001, an everolimus-related compound) in elderly adults, which found improved response to influenza vaccination, a marker of immune function, not a lifespan outcome . There are also small, short-duration observational and pilot studies in humans looking at intermittent low-dose sirolimus for markers like frailty, periodontal health, and immune aging markers, run by researchers such as those associated with the PEARL trial (a University of California, Los Angeles-affiliated study on periodontal and inflammatory markers in older adults on low-dose rapamycin). These studies are small, typically under 100 participants, run for months not years, and measure biomarkers, not survival. No trial has followed people on sirolimus or everolimus for years to measure whether they actually live longer or stay healthier longer than untreated controls. That is the single most important sentence in this entire article, and it's true regardless of which of the two drugs someone is asking about.

Which drug do off-label longevity protocols actually use?

Sirolimus, almost exclusively. The intermittent weekly or biweekly low-dose protocols that circulate among longevity-focused physicians and patients (typically in the 3mg to 6mg per week range for sirolimus, though exact numbers vary by prescriber and patient weight) are based on the animal literature and on transplant-medicine pharmacokinetic data, adapted down from the daily immunosuppressive dosing used in kidney transplant patients ^[2]. Everolimus shows up far less often in these protocols, mostly because its shorter half-life means it would require dosing closer to daily to maintain any meaningful mTOR inhibition, which starts to look more like continuous immunosuppression, the thing intermittent dosing is specifically designed to avoid. If you're comparing the two for an off-label longevity purpose, sirolimus has both the deeper mouse evidence base and the dosing profile (long half-life, allows for pulsed weekly use) that makes intermittent low-dose protocols pharmacologically sensible in the first place. Details on the dosing itself, including calculating a starting point by weight, are covered separately: see Sirolimus Rx dosage and the Sirolimus Rx dosage calculator.

What are the real risks of sirolimus and everolimus?

Both drugs are FDA-approved immunosuppressants, and immunosuppression is the core risk, not a side note. At transplant-level continuous daily dosing, sirolimus increases infection risk and impairs wound healing, which is why the FDA label carries specific warnings about surgical wound complications, including dehiscence, in transplant patients ^[2]. Lower, intermittent dosing used off-label for longevity is intended to reduce this risk, but there is no long-term safety data confirming it eliminates the risk, because no long-term study has been run. Mouth ulcers (stomatitis) are one of the most common side effects reported at almost any dose, including in the low-dose longevity context; they show up in the prescribing information for both drugs and are frequently reported anecdotally by people on intermittent protocols ^{[2] [3]}. Metabolic effects are the other consistent finding: elevated triglycerides, elevated cholesterol, and in some patients new or worsened insulin resistance and blood glucose elevation. These are listed in the official prescribing information for both Rapamune and Afinitor as common adverse reactions ^{[2] [3]}. Other effects seen in transplant-dose use include low white blood cell counts, delayed wound healing, and, over long continuous use, increased risk of certain skin cancers. None of this means low-dose intermittent use carries identical risk to transplant dosing, it likely doesn't. But "likely doesn't" is an inference from pharmacology and animal work, not a conclusion from a completed human safety trial at longevity doses. Anyone starting either drug off-label should be doing so with bloodwork monitoring (lipids, glucose, kidney function, complete blood count) and physician oversight, not as a supplement-style purchase.

How do sirolimus and everolimus compare side by side?

Where does Sirolimus fit into this comparison?

Sirolimus Rx is a provider-reviewed telehealth route for people whose physician has decided, after reviewing labs and history, that off-label sirolimus makes sense for them. It does not compound or manufacture the drug; prescriptions are filled through a licensed pharmacy partner, and the drug itself is the same sirolimus molecule covered throughout this article, not a proprietary formulation. If you've read the mouse data, understood that it does not (yet) prove a human lifespan benefit, and want to move forward anyway with physician oversight, that's a reasonable, informed decision for some people; it is not a decision to make without bloodwork and follow-up. The practical side (dosing, injection technique if using an injectable route, cycle length) is covered in the dosing hub: how to reconstitute Sirolimus Rx, Sirolimus Rx how to inject, Sirolimus Rx injection sites, and Sirolimus Rx cycle length.

Which one should a longevity-focused prescriber actually consider?

Based on the public evidence, sirolimus is the better-supported choice for anyone pursuing an off-label mTOR-inhibition strategy for aging, simply because it's the molecule the mouse lifespan data is built around and the one with a pharmacokinetic profile (long half-life) suited to intermittent dosing. Everolimus has real, FDA-approved uses that matter enormously in oncology and transplant medicine, but it hasn't been through the same longevity-focused animal testing pipeline, and its shorter half-life makes the intermittent low-dose approach less pharmacologically clean. Neither drug has a completed human trial showing lifespan extension. That single fact should anchor every decision here. Choosing sirolimus over everolimus for longevity purposes is choosing the better-evidenced animal model and the more practical dosing profile, not choosing a proven human intervention. Anyone presenting this as a settled question, in either direction, is overselling what the data supports.

Frequently asked questions

Is rapamycin the same as sirolimus?

Yes. Rapamycin is the original name for the compound isolated from a soil bacterium on Rapa Nui (Easter Island); sirolimus is its generic drug name once developed pharmaceutically. They are chemically identical, sold under brand names like Rapamune. There is no difference to weigh, it's one drug with two names.

Is everolimus stronger than sirolimus?

Not exactly stronger, but different. Sirolimus tends to more completely inhibit mTORC1 and, at higher exposures, also affects mTORC2. Everolimus has a shorter half-life (around 30 hours vs 57-62 hours for sirolimus) and more predictable pharmacokinetics, which is why it's used where tight blood-level monitoring matters, like some transplant protocols.

Can everolimus be used for longevity instead of sirolimus?

It's not the drug the major longevity animal research is built on. The NIA Interventions Testing Program's repeated positive lifespan findings are with sirolimus, not everolimus. Everolimus's shorter half-life also makes weekly pulsed dosing less practical. Most off-label longevity protocols use sirolimus for these reasons.

Has rapamycin been proven to extend human lifespan?

No. The NIA Interventions Testing Program has shown lifespan extension in mice repeatedly since the original 2009 Nature paper, including when started late in life. No completed human trial has measured whether sirolimus extends human lifespan; the human evidence is limited to small, short studies on biomarkers like immune response, not survival.

What is the FDA-approved use for sirolimus?

Sirolimus (Rapamune) is FDA-approved to prevent organ rejection in kidney transplant patients, approved in 1999. It's also approved as Fyarro for a rare cancer called malignant PEComa and as Hyftor, a topical gel, for facial angiofibromas in tuberous sclerosis. Longevity use is entirely off-label.

What is everolimus approved to treat?

Everolimus (Afinitor) is FDA-approved for advanced kidney cancer, certain breast cancers, pancreatic neuroendocrine tumors, and tuberous sclerosis complex. As Zortress, it's approved to prevent transplant rejection. It was first approved in 2009. No approval covers aging or lifespan extension.

What are the main side effects of sirolimus and everolimus?

Both carry immunosuppression risk, mouth ulcers (stomatitis), elevated cholesterol and triglycerides, and in some patients elevated blood glucose or new insulin resistance. At transplant-level continuous dosing, sirolimus also carries warnings about impaired wound healing. These are listed in each drug's FDA prescribing information.

Why do people use sirolimus intermittently instead of daily for longevity?

Intermittent (weekly or biweekly) low-dose protocols are designed to get periodic mTOR inhibition while limiting the continuous immunosuppression seen with daily transplant dosing. This approach is based on pharmacokinetic reasoning and animal studies, not a completed human trial confirming it's safer long-term than daily dosing.

Is sirolimus a controlled substance?

No. Sirolimus is a prescription drug but not a DEA-scheduled controlled substance. It still requires a prescription and, for off-label longevity use, ideally physician oversight with bloodwork, because of its immunosuppressive effects and metabolic side effect profile.

Does the NIA Interventions Testing Program test everolimus too?

The ITP's headline, repeated lifespan-extension results are specifically with sirolimus, tested since 2006 across three research sites. Everolimus has not been through the same standardized lifespan testing pipeline, so the strong animal evidence people cite for mTOR inhibition and longevity is a sirolimus story, not an everolimus one.

What half-life difference matters most for dosing?

Sirolimus's half-life is roughly 57 to 62 hours, versus about 30 hours for everolimus. The longer half-life is why sirolimus suits weekly or biweekly pulsed dosing; everolimus would need more frequent dosing to maintain similar mTOR inhibition, pushing it closer to continuous exposure.

Can a doctor legally prescribe sirolimus off-label for aging?

Yes. Once the FDA approves a drug, physicians can legally prescribe it off-label for other uses based on clinical judgment, which is standard practice across medicine. It means the FDA hasn't reviewed evidence for that specific use, in this case aging, so the burden of evidence rests on the physician and the existing research literature.

Sources

1. NIH National Institute on Aging, rapamycin discovery background: Rapamycin was isolated from a bacterium found on Easter Island (Rapa Nui) in the 1970s
2. FDA, Hyftor (topical sirolimus) approval: Hyftor is FDA-approved as a topical sirolimus gel for facial angiofibromas in tuberous sclerosis complex
3. FDA, Afinitor (everolimus) prescribing information: Everolimus (Afinitor) FDA approval history, approved cancer indications, and common adverse reactions
4. NIH National Institute on Aging, Interventions Testing Program overview: Sirolimus and related compounds act through inhibition of mTOR signaling, the mechanism studied in the ITP
5. Harrison DE et al., Nature 2009, 'Rapamycin fed late in life extends lifespan in genetically heterogeneous mice': Rapamycin extended lifespan in genetically heterogeneous mice even when treatment began at 600 days of age
6. Mannick JB et al., Science Translational Medicine 2014: An mTOR inhibitor improved influenza vaccine response in elderly human subjects, a short-term immune biomarker study, not a lifespan trial