Rapamycin: mTOR, weekly dosing, and what the evidence does and does not show

An approved transplant drug with the most consistent lifespan-extension record of any molecule in animal studies, used off-label at a fraction of the transplant amount and a seventh of the frequency. What the weekly interval is trying to achieve, and where the human evidence stops.

Two complexes, and why the interval is the whole design

mTOR is a kinase that sits at the centre of the cell's decision about whether to grow or to recycle. It exists in two complexes. mTORC1 senses amino acids, energy and growth factors and drives protein synthesis while suppressing autophagy; mTORC2 is involved in insulin signalling and cytoskeletal organisation. Rapamycin inhibits mTORC1 acutely and selectively. It inhibits mTORC2 only with sustained exposure — and mTORC2 inhibition is where the glucose intolerance and much of the immunosuppression come from.

Off-label or community practice That distinction is the entire argument for weekly rather than daily administration. The modelled half-life is about two and a half days, so a weekly interval allows the level to fall substantially between doses, which is intended to give intermittent mTORC1 inhibition without the sustained exposure that engages mTORC2. Whether that separation holds cleanly in humans at the amounts used is inference from cell and animal work rather than something demonstrated in a human trial. It is a well-reasoned protocol built on an incompletely tested premise, and it should be described that way.

What the animal evidence shows, and what human data exists

Established clinical use The animal record is unusually strong. The National Institute on Aging's Interventions Testing Program — a multi-site programme designed specifically to weed out results that do not replicate — found rapamycin extended median and maximum lifespan in genetically heterogeneous mice, and did so when started at 600 days of age, which is roughly late middle age. Lifespan extension has since been reproduced in yeast, worms, flies and mice. Very few interventions have that record.

Animal-only or theoretical Human evidence for the longevity use is another matter. A small randomised trial of an mTOR inhibitor in older adults reported improved response to influenza vaccination, which is a measure of immune ageing rather than of lifespan. A placebo-controlled trial of weekly rapamycin in healthy adults has reported on safety and self-reported outcomes over a year. Dogs are being studied in an ongoing programme. None of that is a lifespan result in humans, and no such result exists.

The honest summary is that the mechanism is real, the animal data is the best in the field, the human data covers safety and surrogate markers over months rather than outcomes over decades, and the gap between those two statements is where all the uncertainty lives.

The adverse effects that actually turn up

Aphthous ulcers — mouth sores — are the most common complaint at intermittent amounts and are usually the first sign that the amount is too high for that person. Lipid elevation, particularly triglycerides, is well documented at transplant amounts and is reported at intermittent ones. Glucose intolerance is the effect most closely tied to sustained exposure and is the reason fasting glucose is on the panel.

Impaired wound healing and immunosuppression are the two that change what someone should do rather than what they should watch. Both are dose- and exposure-dependent, both are established at transplant amounts, and both are reasons the timing of any planned surgery, dental procedure or live vaccine is a conversation to have in advance rather than afterwards. Rapamycin also has substantial interactions through CYP3A4 and P-glycoprotein — grapefruit, several antifungals and several antibiotics among them — which is one of the clearer cases for a prescriber holding the whole medication list.

None of this is a page's decision to make. Rapamycin requires a prescription, the off-label use is genuinely off-label, and the person weighing an ulcer or a lipid panel against the reason someone started should be the clinician who prescribed it.

How long one dose lasts

Try other intervals on the half-life and steady-state calculator, which runs the same function against whatever cadence you type.

The dosing rows the app records

Established clinical use Reproduced from the app’s reference so you can see what it holds, not as a recommendation. Which row applies to a particular person, if any, is a clinical decision this page does not make — and rows describing supraphysiological or post-cycle use are filtered out before this table is built, so what you see here is a subset.

What the app monitors alongside it

The panel below is the app’s own monitoring note for Rapamycin, verbatim. The analytes in it that have a page here are linked; those pages cover what each one measures, which assay produced it and how to read a trend.

• HbA1c and fasting glucose

Drawbacks and risks the app records

From the app's own entry, and note that it mixes transplant-dose effects with intermittent-dose ones. That distinction matters more here than on most compounds: several of these are established at daily transplant amounts and are the specific thing weekly administration is designed to avoid.

• FDA approved only as immunosuppressant — off-label longevity use
• Immunosuppression at higher doses — infection risk
• Wound healing impairment at therapeutic doses
• Mouth sores (aphthous ulcers) common
• Lipid elevation in some users
• Requires physician oversight — not OTC
• Immunosuppression at transplant doses
• Impairs wound healing
• Elevated triglycerides
• Must be physician prescribed and supervised
• Significant drug interactions
• Long-term longevity use safety data still emerging

Interaction rules that name Rapamycin

From the app’s interaction data, filtered so no rule naming a compound this site does not publish appears. Not exhaustive, and not a safety clearance: a combination that is not listed is one nobody has documented here, which is not the same as one that is fine. The combination checker has the rest.

Questions people actually ask

Why weekly rather than daily?

To let the level fall far enough between doses that mTORC2 is not sustainedly inhibited, while still inhibiting mTORC1 periodically. That is the rationale. It rests on the differential sensitivity of the two complexes, which is established in cells, and on the assumption that a weekly interval achieves the separation in people, which is not directly demonstrated.

Is rapamycin the same as sirolimus?

Yes — sirolimus is the generic name and rapamycin the original. Everolimus is a related but distinct molecule with a shorter half-life, and results from one do not transfer automatically to the other.

How long does one dose last?

The app models a half-life of about two and a half days, so roughly five days for most of a dose to clear and about twelve for it to be effectively gone. The curve on this page is drawn with the app's own function; the half-life calculator will run other intervals.

What does the monitoring panel look for?

Fasting glucose and lipids because those are the metabolic effects, a complete blood count because immunosuppression shows up there, and a deliberate check for mouth sores and wound healing because those are the early clinical signals. The app's panel is in the monitoring section above.

Where the load-bearing numbers come from

Named rather than linked. Publisher URLs move, and a citation that resolves to a 404 two years from now is worse than one you can search for by name — every entry below is findable from the title and year alone.