Evaluation of furosemide-loaded alginate microspheres prepared by ionotropic external gelation technique.

Alginate microspheres containing furosemide were prepared by the ionotropic external gelation technique using Ca2+, Al3+ and Ba2+ ions. The incorporation efficiency of the prepared microspheres ranged between 65% and 93%. The effect of sodium alginate concentration, cross-linking ions and drying conditions was evaluated with respect to entrapment efficiency, particle size, surface characteristics and in vitro release behavior. Infrared spectroscopic study confirmed the drug-polymer compatibility. Differential scanning calorimetric analysis revealed that the drug was molecularly dispersed in the alginate microsphere matrices. Scanning electron microscopic study of microspheres showed the rough surface due to higher concentration of drug molecules dispersed at molecular level in the alginate matrices. The mean particle size and entrapment efficiency were found to be varied by changing various formulation parameters. The in vitro release profile could be altered significantly by changing various formulation parameters to give a sustained release of drug from the microspheres. The kinetic modeling of the release data indicate that furosemide release from the alginate microspheres follow anomalous transport mechanism after an initial lag period when the drug release mechanism was found to be Fickian diffusion controlled.