As far as I can see "Penetrex" is used in two different ways.

One refers to a now-discontinued antibiotic - see http://www.drugs.com/mtm/penetrex.html for more on this.

The other use refers to a product which is apparently made by a company called Penetrex (http://penetrex.com/).

From a look at the Q&A section of that site, there are lots of superficially impressive-sounding "sciency" words there, none of which make the slightest sense to me as a non-clinical biomedical professional.

I suggest that you check out that Q&A section and then decide for yourself.