Design of pH-dependent dissolving microparticles of piroxicam and evaluation of their dissolution characteristics

The purpose of this study is preparation and evaluation of enteric release piroxicam microparticles having soild dispersion structure in presence of Eudragit S100 to improve the dissolution rate and reduce the local gastrointestinal irritation of piroxicam. Microparticles were prepared by spherical crystallization method with different ratio of drug, Eudragit S100 (enteric polymer) and Aerosil as an antiadhesion agent. The micromeritic properties such as particle size, shape and flowability were investigated and in vitro release characteristics of microparticles were evaluated. The physical state of piroxicam in microparticles was analysed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffractometry. The stability of microspheres was also evaluated in a 3-month accelerating condition stability. The results showed that spherical and uniform microparticles were obtained with high encapsulation efficiency (>90%) and improved micromeritics properties. The physical state investigations indicated that crystalline form of piroxicam in microparticles was disordered, suggesting that piroxicam was highly dispersed in microparticles as amorphous state. Also microparticles were stable after 3 mounth storage in accelerating conditions. Drug release studies showed that piroxicam in microparticles was well protected in an acidic medium and increased dissolution rate in basic medium from the polymeric solid molecular dispersion as compared with the crystalline pure drug. Thus, present study demonstrated the high potential of spherical crystallization technique for obtaining stable microparticles of poorly water soluble drugs using enteric polymers carriers.