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.