Abstract: A sustained release of ibuprofen granules coated with ethyl cellulose has beenstudied both in vitro and in vivo with a selected formulation。The drug release process follows Higuchiequation when coating extent is low,and zero-order kinetics when coating extent is high.The primaryfactors that influence drug release include granule size ,coating extent ,pH of dissolution medium andpressure,The release rate decreases when either granule size or coating extent increases or pH valuedecreases.The release rate increases greatly when the coated granules are compressed directly intotablets in that the coating film is destroyed.The results from oral administration of coated granules byseven healthy volunteers show that the in vitro and in vivo correlation of drug release from coatedgranules is highly significant.