Rapamycin
Also known as: Sirolimus, Rapamune
mTOR Inhibitor | Longevity & Immunosuppression
Overview
Rapamycin (sirolimus) is a macrolide compound originally discovered in 1972 from a soil bacterium (Streptomyces hygroscopicus) found on Easter Island (Rapa Nui). It was FDA-approved in 1999 as an immunosuppressant for the prevention of organ transplant rejection and has since become the most studied pharmacological intervention for lifespan extension. Rapamycin is the only drug that has consistently extended lifespan in every organism tested, including yeast, worms, flies, and mice, making it the benchmark compound in longevity research. At immunosuppressive doses (daily administration), it prevents transplant rejection and treats certain cancers. At lower pulsed doses (weekly administration), it is increasingly used off-label in the longevity community to target aging-related pathways while minimizing immunosuppressive side effects. The distinction between daily immunosuppressive dosing and weekly pulsed longevity dosing is critical, as the side effect profiles differ substantially between these two regimens.
Key benefits
- Lifespan extension demonstrated in every model organism tested (yeast, worms, flies, mice)
- Upregulation of autophagy and cellular quality control mechanisms
- Reduction of senescent cell burden and associated inflammatory secretome
- Improved immune function at low pulsed doses (paradoxical immune enhancement)
- Reduced age-related inflammation (inflammaging) via mTORC1 inhibition
- Enhanced mitochondrial function and biogenesis
- Potential reduction in age-related cancer risk through growth pathway suppression
- Improved vaccine response in elderly populations at low intermittent doses
Mechanism of action
Rapamycin exerts its effects by binding to the intracellular protein FKBP12, forming a complex that directly and specifically inhibits mechanistic target of rapamycin complex 1 (mTORC1). mTORC1 is a master nutrient-sensing kinase that integrates signals from growth factors, amino acids, energy status, and stress to regulate cell growth, proliferation, and metabolism. When mTORC1 is active, it promotes anabolic processes including protein synthesis (via S6K1 and 4E-BP1 phosphorylation), lipid synthesis, and nucleotide synthesis while suppressing autophagy. By inhibiting mTORC1, rapamycin shifts the cellular balance from growth toward maintenance and repair: it upregulates autophagy (cellular self-cleaning), enhances mitochondrial function, reduces senescent cell accumulation, improves proteostasis, and reduces chronic low-grade inflammation (inflammaging). With chronic daily dosing, rapamycin can also inhibit mTORC2, which mediates Akt signaling and is responsible for some of the metabolic side effects (insulin resistance, lipid changes). Pulsed weekly dosing preferentially inhibits mTORC1 while allowing mTORC2 to recover between doses, which is believed to account for the improved side effect profile of longevity protocols.
Molecular data
- Type
- Macrolide lactone (C51H79NO13)
- Half-life
- ~62 hours
Indications
What the research community uses this compound for, with self-reported effectiveness.
Longevity / Anti-Aging
Transplant Medicine
Age-Related Disease Prevention
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Delivery method
| Protocol | Dose | Frequency | Duration |
|---|---|---|---|
| — | 5-6 mg once weekly | Once weekly | — |
| — | 1-3 mg once weekly | Once weekly | — |
| — | 8-10 mg every two weeks | Every 14 days | — |
| — | 2-5 mg daily (adjust to trough levels 4-12 ng/mL) | Daily | — |
Protocol variations
Alternative cycling patterns reported in the literature and community.
Weekly Pulsed Longevity Protocol
The most widely adopted longevity protocol involves taking rapamycin once weekly at a dose of 5-6 mg. This approach is supported by the pharmacokinetic rationale that weekly dosing provides transient mTORC1 inhibition (the target for longevity benefits) while the 62-hour half-life allows sufficient drug clearance for mTORC2 to recover before the next dose. Most practitioners recommend cycling (e.g., 8 weeks on, 2-4 weeks off) or continuous use with regular monitoring.
Immunosuppressive Transplant Protocol
The FDA-approved transplant protocol uses daily rapamycin dosing titrated to maintain trough blood levels of 4-12 ng/mL (or 12-20 ng/mL in some protocols). This is combined with calcineurin inhibitors (tacrolimus or cyclosporine) and corticosteroids. Daily dosing results in sustained inhibition of both mTORC1 and mTORC2, which accounts for the more significant side effect profile including immunosuppression, metabolic dysregulation, and impaired wound healing.
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Common side effects
- Mouth sores / aphthous ulcers (most common, usually dose-dependent and self-limiting)
- Mild lipid changes (elevated LDL cholesterol and triglycerides)
- Temporary glucose elevation or mildly impaired fasting glucose
- Mild gastrointestinal discomfort (nausea, loose stools)
- Skin changes (mild acne, slower wound healing at injection/cut sites)
Rare side effects
- Clinically significant immunosuppression (primarily at daily transplant doses)
- Severe hyperlipidemia requiring statin intervention
- Insulin resistance or new-onset impaired glucose tolerance
- Interstitial pneumonitis (very rare, primarily at immunosuppressive doses)
- Impaired wound healing requiring dose interruption before elective surgery
- Peripheral edema
- Leukopenia or thrombocytopenia (dose-dependent, mainly at transplant doses)
Contraindications
- Active serious infection or immunocompromised state
- Hypersensitivity to rapamycin/sirolimus or any macrolide compound
- Severe hepatic impairment (rapamycin is extensively hepatically metabolized)
- Planned major surgery within 2-4 weeks (impaired wound healing)
- Pregnancy or breastfeeding
- Concurrent use of strong CYP3A4 inhibitors without dose adjustment (ketoconazole, itraconazole, clarithromycin, grapefruit juice)
Monitoring
- Lipid panel (total cholesterol, LDL, HDL, triglycerides): baseline, 6 weeks, then every 3-6 months
- Fasting glucose and HbA1c: baseline, 6 weeks, then every 3-6 months
- Complete blood count: baseline, then every 6 months
- Liver function tests: baseline, then every 6-12 months
- hsCRP and inflammatory markers: baseline, then every 6 months (optional but informative)
- Oral mucosa inspection at each follow-up visit
References
Primary literature and clinical-trial data informing this entry.