Self-Emulsifying Antibacterial Creamy Ointment Based on Methyl Cellulose and Lavender Essential Oil: Rheology and Drug Release Kinetics

This study presents the formulation and characterization of a self-emulsifying antibacterial creamy ointment comprising methyl cellulose, triacetin, triethyl citrate, and a synergistic blend of benzyl alcohol, phenylethanol, and lavender essential oil. The ointments were designed for topical drug delivery and evaluated for their rheological behavior, essential oil release kinetics, and antimicrobial efficacy. Emulsions were prepared using shear mixing and ultrasonic processing and were characterized by viscoelastic and shear-thinning behavior, modeled via Maxwell, Cross, and Herschel–Bulkley frameworks with thixotropic considerations. Drug release studies employing UV-Vis spectrophotometry showed that gentle mixing enhanced essential oil release, with the Weibull model best fitting the release profiles. Antibacterial testing against E. coli and genetically diverse ten lactic acid bacteria (LAB) revealed that formulations containing aromatic alcohols significantly reduced MIC and MBC values, suggesting synergistic effects. Optical density and bacterial viability models demonstrated improved kill kinetics with mixing, attributed to enhanced dispersion and bioavailability of the essential oil. The results support the development of a robust, spreadable, and potent topical antimicrobial system with potential applications in treating skin infections and limiting the spread of antibiotic-resistant LAB.