In-vivo evaluation of sustained release microspheres of 5-FU in rabbits

Abstract The in-vivo absorption characteristics of 5-fluorouracil (5-FU) encapsulated within ethylcellulose microspheres, prepared by an evaporation/extraction method, were evaluated in rabbits. 5-FU was administered as a solution both intravenously ( n =5, 12 mg/kg) and orally as a single dose ( n =6, 20 mg/kg), and orally as microspheres ( n =5, 20 mg/kg). Statistically significant differences were found between the two oral treatments. The mean residence time and mean absorption time were both considerably increased following microsphere administration compared with the solution. The absolute bioavailabilities of 5-FU from the solution and the microspheres were 5 and 17%, respectively.