Topical Delivery of Erythromycin from Various Formulations: An in Vivo Hairless Mouse Study

Topical products containing erythromycin, a macrolide antibiotic with poor aqueous solubility, are usually formulated as high alcohol content solutions or gels. In this study, we evaluated the deposition of erythromycin base into various strata of hairless mouse skin following topical in vivo application from various low- and nonalcoholic formulations. The formulations tested included a nonionic liposomal formulation composed of glyceryl dilaurate, cholesterol, and polyoxyeth-ylene-10-stearyl ether at a weight ratio of 57:15:28, two nonionic oil-in-water (o/w) liposomal emulsions containing isopropyl myristate or light mineral oil as the oil phase, a conventional o/w emulsion, a 40% hydroalcoholic solution, and two commercially available topical products. Eight hours after topical administration of these formulations, the efficiency of uptake of erythromycin into the living skin strata was in the order: liposomal isopropyl myristate emulsion ≫ liposomal mineral oil emulsion ≫ nonionic liposomes ∼ Emgel ∼ Theramycin-Z ≫ conventional emulsion ≫ hydroalcoholic solution. Alcohol-free liposomal systems are shown to be as efficient as high alcohol content products in facilitating permeation of erythromycin through the stratum corneum into living skin tissue.