Preparation and Evaluation of an Enrofloxacin Self-Micro Emulsion for Veterinary Use

Abstract

We prepared an enrofloxacin self-micro emulsion and optimized the oil, emulsifier and co-emulsifiers using a pseudoternary phase diagram. The ratio of the oil phase to the emulsifier was used as the influencing factor, and the light transmittance was used as the evaluation index. The formulation was optimized using a star design-effect surface method. We examined the preparation versus enrofloxacin solution as the control group at the recommended clinical dosage of enrofloxacin for 7 days in healthy broiler chickens. The optimal formulation was composed of 2.5% enrofloxacin, oil phase 22% isopropyl myristate and 8% benzyl alcohol with the emulsifiers (i.e., 39% EL-40 and 13% Tween-80) and 17.5% 1,2-propanediol as co-emulsifier. The average particle size was 72 nm and emulsification time was 23 sec. The size and distribution of the microemulsion were uniform, and the cumulative dissolution at 30 min was >80%. The mental states, food and water intake of the chickens in the test group were normal as with the blood biochemical indices. Histopathological examination showed no obvious hepatotoxicity. Slight damage to the lung and intestinal mucosa was observed, but the degree of injury was similar to that of the enrofloxacin control solution. The self-micro emulsifying preparation of enrofloxacin possessed the advantages of simple preparation, good appearance, high emulsifying efficiency and good safety; therefore, it has a good application value in a veterinary clinic.