Studies on microencapsulation of 5-fluorouracil with poly(ortho ester) polymers

Microencapsulation of 5-fluorouracil was successfully accomplished with pol y(ortho ester) polymers by the emulsification-solvent evaporation method. W hile actual drug loading increased with increasing drug load (5-15% w/w), t he entrapment efficiency remained essentially unaffected, under a given set of experimental conditions. Incorporation of sorbitan sesquioleate enhance d entrapment efficiency, decreased the volume-surface mean diameter of the poly(ortho ester) microspheres and provided controlled release of 5-fluorou racil. The volume of the aqueous phase was more important than the concentr ation of polyvinyl alcohol in it. The entrapment efficiency improved from 1 3 to 33% when the volume of the aqueous phase was increased from 20 to 80 m l. The volume of organic phase (methylene chloride) and the concentration o f polymer in it played an important role. The use of smaller volumes of mor e concentrated polymer solution enhanced actual drug loading, entrapment ef ficiency and produced larger microspheres. The release studies conducted in 0.01M phosphate buffer at 37 +/- 1.0 degrees C demonstrated that the relea se of 5-FU from the microspheres prepared with sorbitan sequioleate was nea rly independent of the initial drug load with a mean zero-order rate consta nt of 0.0063% per hour. The data suggested that drug release was largely a diffusional process with contributions from dissolution and polymer degrada tion.