Novel Pullulan–Eudragit® S100 blend microparticles for oral delivery of risedronate: Formulation, in vitro evaluation and tableting of blend microparticles

•We formulated Pullulan–Eudragit® S100 blend microparticles containing risedronate.•Pullulan/Eudragit® S100 microparticles showed high encapsulation efficiency.•The amount of Pullulan prolonged the risedronate release.•Gastroresistance was achieved for microparticles with the lowest Pullulan concentration.•Tableted microparticles kept gastroresistance and prolonged release of microparticles.

Polymer blends have been considered a promising strategy to tailor drug release. In order to achieve gastroresistance and controlled release, Pullulan, a polysaccharide, and Eudragit® S100, an enteric polymer were selected to prepare microparticles for oral delivery of risedronate, an antiresorptive drug associated with GI tract injuries. Blend microparticles were prepared by spray-drying technique at 3 Pullulan and Eudragit® S100 ratios (MP2:1, MP1:1 and MP1:2) and were characterized in terms of yield, particle size, encapsulation efficiency, morphology, moisture content, flowability and in vitro drug release profiles. Microparticles presented yields between 31 and 42%, encapsulation efficiencies close to 100%, moisture contents lower than 11%, particle size ranging from 2.9 to 4.8 μm and narrow distribution. In the gastric medium, MP1:2 showed the best gastroresistance profile. In the intestinal fluid, all samples were able to prolong drug release. MP1:2 was compressed into tablets with or without polyvinylpyrrolidone. Both tableted microparticles could be obtained with acceptable average weights, drug content close to 100%, sufficient hardness and low friability. In vitro studies showed that tablets maintained the gastroresistance observed for microparticles and were also able to prolong risedronate release. In conclusion, Pullulan/Eudragit® S100 microparticles are promising alternatives for the oral delivery of risedronate in the future.