Does it depend on “vulnerable” bonds (eg sulfur, double bonds, possibly nitrogen)? Are antioxidants more vulnerable? Are complex molecules more vulnerable?
Including periods of time when it’s 88F
I guess it stores better than antioxidants do bc antioxidants are very easily oxidized. Or anything with free N or S groups or lots of double bonds…
My guess is also that modafinil does not store as well as, say, amphetamine. Modafinil sulfone is def an oxidation byproduct
I don’t worry about this issue at all for the medications I take (common medications, including rapamycin), but it might be an issue for some supplements and biological drugs.
The Harvard Medical School republished a well-worn article in August that recounted a 1985 study in which the U.S. Food and Drug Administration (FDA) looked to pinpoint expiration dates for more than 100 drugs in an effort to unburden the U.S. military from some of the exorbitant annual costs of replacing its pharmaceuticals.
The study showed that 90 per cent of more than 100 drugs, both prescription and over-the-counter, were fine to use well after expiry dates had passed, and in some cases more than 15 years after the expiration date had come and gone.
That being as it may, the Canadian Pharmacists Association says drug manufacturers can only guarantee the potency and safety of the various drugs until the labelled expiry date.
“Beyond that date, we don’t know what happens, we don’t know if it is still effective, we don’t know if it is potentially toxic,” said Jill Hall, a pharmacist and clinical associate professor in the University of Alberta’s Faculty of Pharmacy and Pharmaceutical Sciences.
Practically speaking, Hall said there is a handful of drugs known to degrade quite quickly, such as nitroglycerin tablets, insulin and tetracycline, an antibiotic that may become toxic to the kidneys after it expires.
https://www.ualberta.ca/folio/2018/10/can-i-still-use-prescription-drugs-after-they-expire.html
Rapamycin is way way more complex than most drugs though, there are so many potentially vulnerable bonds that could be attacked by oxidation
Is dry room temp better than refrigerator for long term storage? Or something else?
#shelf-life
Why metformin tablets suck water out of the air so eagerly — and why Adderall usually doesn’t
Chemical reasons
Dynamic-vapour-sorption studies show weight gains of 10-15 % after 48 h at 75 % RH, and tablet assays stored at 40 °C/75 % RH fall below 95 % label in a few months if the pack is not moisture-tight. (IJPPR, Acta Pharmaceutica) Even FDA stability files flag the drug substance as “hygroscopic,” with long-term stability contingent on sealed HDPE or blisters plus desiccant. (FDA Access Data)
Practical takeaway: keep the cotton and desiccant, recap tightly, and don’t stock-pile un-blistered tablets in a pill sorter for weeks.
Result: ordinary humidity seldom changes assay or release rate; the bigger risks to Adderall are heat-accelerated racemization and capsule shell softening, not chemical hydrolysis.
| Property | Metformin HCl | Amphetamine sulfate (Adderall) |
|---|---|---|
| Water uptake at 80 % RH (24–48 h) | 10–15 % (very hygroscopic) | ≤2 % (slightly hygroscopic) |
| Crystal change on hydration | Forms stable monohydrate | No new hydrate formed (already hydrated or anhydrous stays anhydrous) |
| Packaging needed | HDPE + desiccant or foil blisters | Standard HDPE bottle or gelatin/HPMC capsules |
| Typical problems if left open | Tablet swelling, friability, minor assay drift, XR failure | Capsule softening; negligible potency loss |
