Selegiline? Canagliflozin?
I’m noticing acarbose starts to “soften” if dew points are over 68F…
Is hygroscopicity an indication that a medication might last less long under moist/damp conditions like high dew points?
my astaxanthin is also pretty bad
I decided to finally get a humidifier
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here is what claude opus 4 said:
is rapamycin hygroscopic
Edit
Yes, rapamycin (sirolimus) is hygroscopic, meaning it readily absorbs moisture from the air.
Key storage considerations:
- Must be stored in tightly sealed containers
- Protect from humidity and moisture
- Often packaged with desiccants
- Recommended storage at -20°C for long-term stability
- Once exposed to air, degradation accelerates
Why this matters:
- Moisture absorption can lead to chemical degradation
- Affects potency and stability
- Can cause clumping or changes in physical appearance
- May impact bioavailability if used in formulations
Practical implications:
- Research labs typically store it under inert gas (argon/nitrogen)
- Pharmaceutical preparations use special coating or encapsulation
- Compounded formulations must account for moisture sensitivity
- Quick handling recommended when weighing/preparing
Stability data:
- Solid rapamycin is relatively stable when dry
- In solution, degrades faster (especially in aqueous solutions)
- Light-sensitive as well as moisture-sensitive
- Forms degradation products including ring-opened forms
This hygroscopic nature is one reason why rapamycin formulations often use special delivery systems (like nanoparticles or lipid-based carriers) to protect the drug from environmental moisture and improve stability.
Retry
AC
how much faster does rapamycin degrade if dew point is 68F? will it still last for several years?
Edit
At a dew point of 68°F (20°C), which represents very high humidity (about 70-80% RH at typical room temperatures), rapamycin degradation would be significantly accelerated compared to proper storage conditions.
Degradation rate estimates:
- At high humidity (70%+ RH), rapamycin can lose 5-10% potency within 3-6 months
- Compare to properly stored (-20°C, desiccated): <2% loss over 2+ years
- Room temperature + high humidity: degradation rate increases 10-20 fold
Will it last several years?
- Unlikely to maintain acceptable potency (>90%) for several years
- After 1 year at high humidity: expect 15-30% degradation
- After 2 years: could see 40-50%+ potency loss
- Physical changes: clumping, dis
Retry
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Yes—at least in its raw (API) state, rapamycin is officially classified as hygroscopic by major chemical suppliers. Sigma-Aldrich’s product pages for both the dry powder and pre-made solutions carry the instruction “keep container tightly closed … is hygroscopic.” (MilliporeSigma)
Why a “water-insoluble” macrolide can still adsorb moisture
| Factor | Details |
|---|---|
| Functional groups | Rapamycin has eight hydroxyls, three carbonyls, and an ether bridge embedded in its 31-membered lactone. Even though the bulk of the molecule is lipophilic, those polar sites can hydrogen-bond to water at the surface. |
| Amorphous surface area | Commercial rapamycin is milled to a very fine (often partially amorphous) powder to aid dissolution in formulation steps; amorphous regions bind water more readily than a perfect crystal. |
| Solid-state degradation | Once a thin layer of moisture forms, the lactone and triene segments are more prone to hydrolysis and oxidation. Heat-and-humidity stress tests on sirolimus analogues show faster impurity growth under high RH. (PubMed) |
Practical storage guidance
| Form on hand | Humidity risk | Best practice |
|---|---|---|
| Bulk powder (lab-grade) | High—large surface area; moisture can reach >1 % w/w in hours at ≥50 % RH | Keep at −20 °C (or 4 °C if used weekly) inside a desiccator or with fresh silica gel. Warm to room-temp before opening to avoid condensation. |
| Tablets/capsules (e.g., Rapamune®) | Moderate—film coat slows but doesn’t stop ingress; excipients (lactose, MCC, croscarmellose) are also hygroscopic | Leave in foil blisters or the HDPE bottle with the original desiccant. Fill pill-boxes for only 2-3 days at a time and slip in a micro-desiccant pack. |
| Solutions in DMSO/EtOH | Solvent-driven—DMSO and EtOH are themselves hygroscopic; extra water slowly dilutes the drug | Aliquot into amber vials, flush with dry N₂/Ar, store at −20 °C. Discard if the solution turns cloudy. |
Re-drying tip: If your powder has clumped, spread it in a shallow glass dish inside a vacuum desiccator over phosphorus pentoxide or fresh silica gel for ~24 h at room temperature. Avoid heating above 40 °C—the lactone ring hydrolyses quickly when both heat and moisture are present.
Bottom line
Rapamycin (sirolimus) isn’t nearly as water-hungry as sugars, but it does adsorb enough moisture to warrant desiccated, tightly sealed storage. Keeping it below ~30 % RH—especially during warm, humid weather—will preserve its potency and prevent that tell-tale “clumpy” texture or accelerated degradation.