Abstract: Aim Ciprofloxacin polylactic acid microspheres (CFX-PLA-MS) were prepared using solvent evaporation method from a solid-in-oil-in-water emulsion system. Methods Orthogonal experiment was used to optimize the method of CFX-PLA-MS preparation. Microspheres were characterized in terms of morphology, size, encapsulation efficiency, drug loading and in vitro drug release. Results The physical state of CFX-PLA-MS was determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Microspheres formed were spherical with smooth surfaces. Drug was enveloped in microspheres without mixing physically with PLA. The average particle size was 280.80±0.15 μm, with over 90% of microspheres falling in the range of 250-390 μm. The encapsulation efficiency was 65.8%±0.58% and the drug loading was 34.1%±0.51%. In vitro release study revealed a profile of sustained release of ciprofloxacin from CFX-PLA-MS. The accumulated release percentage and half-life (T1/2) of ciprofloxacin microspheres were 84.0% in 53.2 h, and 31.9 h, respectively. Higuchi equation was Q = -0.0043 + 0.0039 t1/2, r = 09941. Conclusion Ciprofloxacin microspheres have been successfully prepared and sustained release of CFX from microspheres is achieved.

Key words: ciprofloxacin, ciprofloxacin, polylactic acid, polylactic acid, microspheres, microspheres, preparation, release in vitro, preparation, release in vitro