I believe any gel, lotion, etc is just going to interfere with the absorption of the rapamycin’
Whether you transcutol or DMSO is up to you. A mixture of DMSO or Transcutol, water, and rapamycin filtered through a fine metal sieve and then transferred to a small spray bottle will deliver the rapamycin to the treatment area with the least amount of waste.
Unless you are using pure rapamycin powder, I would use Transcutol.
If you are trying to deliver rapamycin into the bloodstream then use DMSO
The problem with DMSO is it will carry contaminants into the bloodstream just as it does rapamycin. Since I don’t know what the filler materials are in rapamycin tablets, I prefer transcutol. Plus, I find Transcutol much more pleasant than DMSO
(note: Rapa/Admin first suggested Transcutol as a substitute for DMSO)
Trancutol:
“This excipient offers advantages over other enhancers for it is clear (transparent) non-volatile and nearly odorless. Unlike oleic acid, azone, and DMSO, Transcutol® does not compromise the integrity of the skin structures.”
" Transcutol® has a fully established safety profile."
“It is therefore postulated that the ability of Transcutol to readily penetrate the stratum corneum and strongly interact with the water of the intercellular path is what makes Transcutol unique when compared to other solvents that modify skin permeation.”
“With superior solubilization power, unique physicochemical properties, and well-established safety profile, it is an ideal penetration/permeation enhancer.”
An example of rapamycin with Transcutol being used as a treatment for skin disease:
“Thus, rapamycin was solubilized in a solvent (Transcutol®), which is an excellent permeation agent that enhances drug diffusion through the skin [30].”