Solid lipid microparticles for enhanced dermal delivery of tetracycline HCl.

Acne vulgaris (commonly called acne) is a most common skin disease during adolescence, afflicting more than 85% of teenagers. Topical tetracycline (Tc) is used for mild inflammatory acne and as an adjunct to systemic treatment in more severe forms. Solid lipid microparticles (SLMs) are useful tool for topical delivery because of their biodegradable, biocompatible and low toxic characteristic accompanying with excellent skin hydration, occlusiveness and controlled release properties. The purpose of this study was to prepare Tc-loaded SLMs were produced by the spray drying technique and characterized by scanning electron microscopy, powder X-ray diffractometry and differential scanning calorimetry. In vitro and ex vivo release characteristics of Tc through SLMs and control formulations (aqueous carbopol gel) were evaluated over 24h using a vertical Franz diffusion cell through cellulose acetate membranes and exercised rat skin, respectively. SLM formulations present high encapsulation values above 97% without significant different among formulations (p<0.05). The sustained release pattern of Tc through SLMs was illustrated by in vitro release study. The ex vivo drug skin permeation study revealed that Tc dermal deposition of optimum SLMs formulation was about 7 times that of the control formulations. The enhanced skin penetration and accumulation of Tc observed for Tc-loaded SLMs may increase the efficiency of acne therapy and decrease the associated Tc side effects.