Design, characterization and in vitro evaluation of HPMC K100 M CR loaded Fexofenadine HCl microspheres

The aim of the current study was to formulate Fexofenadine hydrochloride loaded sustained release microspheres using HPMC K100 M CR, a release retardant hydrophilic polymer by solvent evaporation method. The effect of different drug loading on drug content, drug encapsulation efficiency and release of drug was monitored. The studies on in vitro release mechanism were performed using USP paddle method with 900 ml of phosphate buffer (pH 6.8) for 10 h at 100 rpm. The mechanism of the drug release was determined by fitting in vitro release data to various release kinetic models such as the zero order, first order, Higuchi, Hixson Crowell and Korsemeyer-Peppas model and finding R(2) values for the release profile corresponding to each model. The results confirm that the release rate of the drug from the microspheres is highly affected by the drug to polymer ratio. The study finds that Higuchi release kinetics, Korsmeyer-Peppas release kinetics and Hixson-Crowell release kinetics were the major release mechanism. The release mechanism was found to be non-Fickian with increase of polymer content. Scanning electron microscopic technique was performed to obtain the morphological changes due to different drug loading. Differential scanning calorimetry and Fourier transform infra-red spectroscopy was performed to determine any interaction of drug with the polymer. A statistically significant variation in release rate was observed for variation in the amount of HPMC K100 M CR. In the present study, a series of sustained release formulations of Fexofenadine hydrochloride were developed with different drug loading so that these formulations could further be evaluated from the in vivo studies. The formulations were found to be stable and reproducible.