Hydrocortisone skin permeation

Reservoir delivery systems have been developed in a variety of styles, ranging from microcapsules to hollow fibers to liposomes. Hayashi et al. (1994) produced delivery systems by encapsulating proteins and hormones inpoly-L-lactide microspheres by a solvent evaporation method. The release mechanism for hormones entrapped in liposomes was studied by Ho et al (1986). Progesterone and hydrocortisone skin permeation was enhanced by the presence ofthe liposomes no penetration ofthe liposomes was observed. Examples ofthe most common hydrogels employed in reservoir systems are crystalline-rubbery PEG, PAAm, celluloses, PAA, and PHEMA. 

Terpenes continue to be a popular choice as experimental enhancers for delivering materials across skin membranes. For example, L-menthol facilitated in vitro permeation of morphine hydrochloride through hairless rat skin [37], imipramine hydrochloride across rat skin [59], and hydrocortisone through hairless mouse skin [60]. Recently, niaouli oil was found to be the most effective of six essential oils in promoting estradiol penetration through hairless mouse skin [61]. It is noteworthy that there is currently little control on the topical use of most terpenes, and many aromatherapy oils and formulations contain appreciable quantities of these chemicals. Their excessive use offers potential for permeation of hazardous compounds from the same formulations into the skin some terpenes also have pharmacological activity. 

Thermal dependence of the flux of the four permeants (butanol, octanol, hydrocortisone and ARA-A) showed the three more lipophilic molecules exhibited large increases in permeability as the temperature of hairless mouse skin was raised from about 10 to 70°C. In contrast, no further enhancement of hydrocortisone flux was noted at temperatures above approximately 70°C. However, the less lipophilic solute, ARA-A, did not experience significant enhancement in permeability until higher termperatures above 37°C. Permeation of the molecules was either beginning to occur by alternate pathways or coming under dermis control. 

Barry, B. W. and Bennett, S. L. Effect of penetration enhancers on the permeation of mannitol, hydrocortisone and progesterone through human skin. Journal of Pharmacy and Pharmacology 39(7) 535-546, 1987. 

Fig. 5 Effects of Azone and the developmental retarding compounds 4-F2 and 2-F2 on permeation of hydrocortisone across human skin.

Behl, C.R. Flynn, G.L. Linn, E.E. Smith, W.M. Percutaneous absorption of corticosteroids age, site and skin-sectioning influences on rates of permeation of hairless mouse skin by hydrocortisone. J. Pharm. Sci. 1984, 73, 1287-1290. 

The major advantage of in vitro investigation is that the experimental conditions can be controlled more precisely, such that the only major variables are the skin and the test material. Although a potential disadvantage is that little information on the metabolism, distribution and effects of blood flow on permeation may be obtained, it has been reported that such procedures were more effective than several other methods for the assessment of differential delivery of hydrocortisone from commercial formulations (Lehman et al. 1996). In vitro systems... 

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