DMSO.org claims the following:
"[DMSO] is more successful ferrying some drugs, such as morphine sulfate, penicillin, steroids, and cortisone, than others, such as insulin."
All of these drugs that it is said to carry are much larger than a single DMSO molecule.
So what is the general mechanism by which DMSO can bring these relatively high-molecular weight compounds into your body transdermally, where they would not do so otherwise? Does it simply “wrap them up” in a large complex, or does it possibly just complex the portions of the other compound that prevent it from crossing transdermally? What is it about insulin for example that prevents it from being carried through the skin?
A quick internet search will give pages of documents basically saying “this is what it does” but I’ve never found a remotely technical explanation of how this works, particularly for large molecules. That’s what I’m asking here.
NOTE 1: I have never used DMSO medicinally and currently have no intentions of doing so.
NOTE 2: I hope this is not considered a duplicate of this question as the answer is specific to the transport of small molecules.