Sustained release Eudragit RL/RS microspheres encapsulating nifedipine were prepared using the acetone/liquid paraffin emulsion solvent evaporation method. The influence of different preparation factors on release o...Sustained release Eudragit RL/RS microspheres encapsulating nifedipine were prepared using the acetone/liquid paraffin emulsion solvent evaporation method. The influence of different preparation factors on release of the drug in vitro was investigated. The release rate of nifedipine from the microspheres increased with increasing Eudragit RL/RS ratio and stirring rate during the preparation, and with decreasing the polymer concentration of internal phase and microsphere size. It was found that a linear relationship existed between the microsphere size and the time of 50% drug release. The drug release rate increased with increasing nifedipine content from 4.2 to 16.7% and was more rapid than the dissolution rate of pure nifedipine particles. However, the release rate of the microspheres with 26.6% drug content decreased significantly and was slower than the dissolution rate of pure drug particles. This was attributed mainly to the nifedipine dispersion state in the microspheres as confirmed by the differential thermal analysis and X ray diffraction study, which showed that nifedipine was present in an amorphous or molecular state in the microspheres with 4.2, 9.4 and 16.7% drug, whereas partly in the crystalline state in the microspheres with 26.6% drug. The amounts released for less than 70% nifedipine can be fitted to Higuchi square root of time model, independent of polymer ratio, drug content and microsphere size.展开更多
Tizanidine hydrochloride(THCl)is an antispasmodic agent which undergoes extensive first pass metabolism making it a possible candidate for buccal delivery.The aim of this study was to prepare a monolayered buccal patc...Tizanidine hydrochloride(THCl)is an antispasmodic agent which undergoes extensive first pass metabolism making it a possible candidate for buccal delivery.The aim of this study was to prepare a monolayered buccal patch containing THCl using the emulsification solvent evaporation method.Fourteen formulations were prepared using the polymers Eudragit■ RS 100 or EudragitB RL 100 and chitosan.Polymer solutions in acetone were combined with a THCl aqueous solution(in some cases containing chitosan)by homogenization at 9000 rpm for 2 min in the presence of triethyl citrate as plasticizer and cast in novel Teflon molds.Physicochemical properties such as film thickness,in vitro drug release and in vitro mucoadhesion were evaluated after which permeation across sheep buccal mucosa was examined in terms of flux and lag time.Formulations prepared using a Eudragit■polymer alone exhibited sa tisfactory physicomechanical properties but lacked a gradual in vitro drug release pattern.Incorporation of chitosan into formulations resulted in the formation of a porous structure which did exhibit gradual release of drug.In conclusion,THCl can be delivered by a buccal patch formulated as a blend of Eudragit■ and chitosan,the latter being necessary to achieve gradual drug release.展开更多
文摘Sustained release Eudragit RL/RS microspheres encapsulating nifedipine were prepared using the acetone/liquid paraffin emulsion solvent evaporation method. The influence of different preparation factors on release of the drug in vitro was investigated. The release rate of nifedipine from the microspheres increased with increasing Eudragit RL/RS ratio and stirring rate during the preparation, and with decreasing the polymer concentration of internal phase and microsphere size. It was found that a linear relationship existed between the microsphere size and the time of 50% drug release. The drug release rate increased with increasing nifedipine content from 4.2 to 16.7% and was more rapid than the dissolution rate of pure nifedipine particles. However, the release rate of the microspheres with 26.6% drug content decreased significantly and was slower than the dissolution rate of pure drug particles. This was attributed mainly to the nifedipine dispersion state in the microspheres as confirmed by the differential thermal analysis and X ray diffraction study, which showed that nifedipine was present in an amorphous or molecular state in the microspheres with 4.2, 9.4 and 16.7% drug, whereas partly in the crystalline state in the microspheres with 26.6% drug. The amounts released for less than 70% nifedipine can be fitted to Higuchi square root of time model, independent of polymer ratio, drug content and microsphere size.
文摘Tizanidine hydrochloride(THCl)is an antispasmodic agent which undergoes extensive first pass metabolism making it a possible candidate for buccal delivery.The aim of this study was to prepare a monolayered buccal patch containing THCl using the emulsification solvent evaporation method.Fourteen formulations were prepared using the polymers Eudragit■ RS 100 or EudragitB RL 100 and chitosan.Polymer solutions in acetone were combined with a THCl aqueous solution(in some cases containing chitosan)by homogenization at 9000 rpm for 2 min in the presence of triethyl citrate as plasticizer and cast in novel Teflon molds.Physicochemical properties such as film thickness,in vitro drug release and in vitro mucoadhesion were evaluated after which permeation across sheep buccal mucosa was examined in terms of flux and lag time.Formulations prepared using a Eudragit■polymer alone exhibited sa tisfactory physicomechanical properties but lacked a gradual in vitro drug release pattern.Incorporation of chitosan into formulations resulted in the formation of a porous structure which did exhibit gradual release of drug.In conclusion,THCl can be delivered by a buccal patch formulated as a blend of Eudragit■ and chitosan,the latter being necessary to achieve gradual drug release.
