Hydrocortisone (cortisol) concentration and penetration gradient.

Hydrocortisone (Cortisol) was incorporated into four different ointments at four concentrations (0.1% 0.3%, 1%, and 3%) and the amounts of the drug penetrating from these preparations into the different layers of excised skin were investigated. The effect of removing the horny layer on the penetration was also determined. Below a level of 1% ointments with intact horny layer and 0.3% with removed layer, a change in the ointment concentration alters the tissue concentration in the ratio 1:1. Above this level doubling of the concentration in the ointments causes an increase of tissue concentrations of only 20-50%. The removal of the horny layer increases the dermal concentrations 100 fold at each ointment concentration. Furthermore, a vasoconstriction test was performed with the different ointments. An increase in the concentrations above the 1% level failed to increase the effect on the vascular system of the skin. The in vitro and in vivo results are discussed with respect to the consequences on affected skin and the therapeutic efficacy of steroid preparations of different concentrations.