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.