Design, development and bioavailability assessment of Oxytetracycline hydrochloride double o/w/o microemulsion formulation

The aim of this research was to improve the oral bioavailability of Oxytetracycline hydrochloride, a broad spectrum antibiotic having poor oral bioavailability, through the formulation of double o/w/o microemulsion systems. The range of compositions forming a clear one-phase region (primary o/w microemulsion) was evaluated through the construction of the ternary diagram and then three different types of double microemulsions were prepared using the "two-step technology". The formulations were characterized for droplet size and zeta potential. DSC was used for determining the type of microemulsion and to verify the formation of double microemulsion systems. The physical characterization gave satisfactory results that were compatible with double microemulsion systems. Finally, the pharmacokinetics of microemulsions was evaluated after oral administration on rats and compared to that of an aqueous and an oily solution. Results indicated an oral bioavailability enhancement of 5.7 and 2 times over the aqueous and oily solutions, respectively.