Deep tissue penetration of bases and steroids after dermal application in rat.

The local deep tissue penetration of bases such as diazepam, antipyrine, iodoantipyrine, haloperidol and steroids such as hydrocortisone, fluocinolone acetonide, testosterone and progesterone after dermal application as aqueous solutions was studied in a rat model. The extent of local, as distinct from systemic delivery, for each solute was assessed by comparing the tissue concentrations obtained below a treated site with those in contralateral tissues. Local direct penetration was evident for all solutes below the applied site, although depth of penetration varied between individual solutes. A physiological pharmacokinetic model was employed to estimate local tissue concentrations of various compounds after dermal application.