Why would diclofenac have a higher skin permeability when formulated as diclofenac epolamine rather than diclofenac sodium? There is a suggestion on the literature that the formation of ion pairs creates a permeation enhancement.
Usually only non-ionised compounds penetrate the skin.
Is it possible that the conjugate species does so?
Some sources claim the epolamine salt has enhanced solubility, others say it is about the same.
Appreciate any help
Voltaren is a 1 -2% paste of the ammonium salt of diclofenac (epolamine is hydroxyethyl pyrrolidine) and is used a topical pain reliever. You can smell the ammonia.

It could be that the increased pH of the paste softens skin and makes it more permeable. High pH will peel your skin right off!