Design and evaluation of biodegradable enteric microcapsules of amifostine for oral delivery

Amifostine is the first FDA approved cytoprotective and chemoprotective agent in the treatment of cancer. However, it is not used widely because of its ineffectiveness when administered orally. The objective of this study was to prepare and evaluate the radioprotective efficacy of orally active amifostine enteric microcapsules (amifostine mc). The microcapsules were prepared by spray drying technique using Eudragit L100-55, and the yield was more than 80%. The particle size and surface morphology were determined by particle analyzer and scanning electron microscopy. Thermal characterization and infrared spectroscopy were evaluated as well. In vitro release assay found that more than 60% amifostine was released during the first 4h and the cumulative release ratio was up to approximately 90% in 24h at 37°C. The radioprotective efficacy was determined by 30-day survival study in mice acutely exposed to 6 Gy γ-ray irradiation. The results showed that all dose groups of amifostine microcapsules could significantly improve survival animal numbers and time. Furthermore, tissue distribution studies indicated the concentrations of the active metabolite WR-1065 in mice tissues of microcapsule group were higher than that of oral amifostine group at 180 min (p<0.01). These results demonstrated that oral administration of amifostine microcapsules provided effective radioprotection compared to the bulk drug.