The influence of the delivery systems over the permeation of an hydrophilic active

Resumo

Over the years different strategies have been employed to increase the efficacy and safety of not only topical and transdermal medicines, but also of cosmetics. The encapsulation technology has enabled the development of multifunctional biodegradable polymers claiming permeation enhancement features, controlled release or protective properties. The objective of this study was to test the performance of a natural polymer- alginate- in the encapsulation of a model hydrophilic permeant- caffeine. The model permeant was encapsulated into three different alginate systems - dry beads, hydrated beads and calcium-alginate microparticles. Additionally, free caffeine was included in three passive formulations - an aqueous solution, a Carbopol© gel and an O/W cream. In vitro diffusion studies with Franz cells were conducted using silastic membranes as a model for human epidermis. Equal amounts of the different caffeine formulations were placed in the donor compartment of the diffusion cells. Samples of the receptor phase were collected every 2 hours for 8 hours. The multiple steady-state fluxes of caffeine were determined. High flux values were achieved with the O/W cream and dry alginate beads. Conversely, the release rate of caffeine was the lowest when caffeine was encapsulated in hydrated beads and alginate microspheres. The different permeation profiles obtained with hydrated and dry beads are probably attributable to the porous nature of the latter and also to an ion exchange mechanism. These results indicate that this encapsulation technology can be successfully used to modulate the bioavailability of molecules for transdermal administration. Alginate polymers seem suitable to be employed in the controlled release of drugs with a high pharmacological potency and small therapeutic windows. On the other hand, its applicability can be extended to cosmetic ingredients that, for safety reasons, should be limited to the superficial layers of the skin.