Skin permeation of different steroid hormones from polymeric coated liposomal formulations

In this study, the effect of various polymers (polycarbophil, chitosan–EDTA, polymeric emulsifier and carrageenan) on the permeation, the chemical and microbial stability of 17-β-estradiol, progesterone, cyproterone acetate (cpa) and finasteride incorporated in DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) liposomes has been investigated. The liposomes contained 1% (w/w) of the steroid hormones. Standard diffusion experiments were performed. Drug stability was monitored by analysing the steroid hormone content in the different formulations over a time period of 8 weeks and visually inspecting for microbial contamination. In addition, viscosity measurements were performed. The permeation rate could be improved by addition of polymeric agents depending on their type and drug. In all tested formulations, finasteride exhibited the highest diffusion. Both the chemical and the microbial stability of the hormones were significantly improved by the polymers in comparison to the pure liposomes after an observation period of 8 weeks. After that time microbial stability was still evident for all semisolid formulations. In contrast to this in the pure liposomes already after 2 weeks the steroid drugs showed complete insufficient chemical stability and microbial contamination. Additional rheological measurements indicated an influence of the polymers and drugs on the viscosity in all formulations. The elasticity predominated in nearly all polymeric formulations.