Rapamycin: Off-Label Pulsatile Dosing
Rapamycin (sirolimus) is currently the most robust lifespan-extending pharmacological agent across multiple animal models. Translating this to humans requires navigating the difference between chronic immunosuppression and pulsatile mTOR inhibition.
The mTOR Dilemma: Complex 1 vs Complex 2
The mechanistic target of rapamycin (mTOR) exists in two distinct complexes. mTORC1 drives cellular growth, protein synthesis, and inhibits autophagy. Inhibiting mTORC1 is the primary goal for lifespan extension. mTORC2 is crucial for cell survival, insulin signaling, and actin cytoskeleton organization. Chronic inhibition of mTORC2 leads to glucose intolerance and immunosuppression.
Daily dosing of rapamycin (as used in transplant patients to prevent organ rejection) chronically suppresses both mTORC1 and mTORC2.
The Case for Pulsatile Dosing
Because rapamycin binds to mTORC1 much more readily than to mTORC2, a pharmacokinetic window exists. By dosing periodically (e.g., once weekly) rather than daily, the drug spikes high enough to inhibit mTORC1 and trigger autophagy, but clears the system before causing significant suppression of mTORC2.
Current Clinical Regimens (Observational)
Note: These are observed regimens from clinical practice (such as those described by Dr. Peter Attia and Dr. Alan Green), not FDA-approved protocols.
- Dose: 3mg to 6mg
- Frequency: Once weekly (every 7 days)
- Administration: Oral (enteric-coated tablets are preferred due to the poor bioavailability and gastric degradation of powder/compounded forms).
- Monitoring: Complete Metabolic Panel (monitoring glucose/HbA1c), Lipid Panel (rapamycin can elevate lipids), and Complete Blood Count.
Grapefruit Juice & Bioavailability
Rapamycin is metabolized by the CYP3A4 enzyme in the liver. Furanocoumarins found in grapefruit juice strongly inhibit CYP3A4. Some clinicians and patients utilize grapefruit juice concurrently with a lower dose of rapamycin to achieve a higher area under the curve (AUC), effectively getting a "6mg effect" from a 2mg dose. While cost-effective, this introduces significant variability and unpredictability in dosing.
Medical Disclaimer
Information presented here is for educational purposes only and does not constitute medical advice. Rapamycin is a prescription medication with potent effects and should only be used under the direct supervision of a licensed physician.