الفهرس 
Preparation and evaluation of pH sensitive microparticles for colonic targeting
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Abstract
Spherical, uniform, smooth surfaced microparticles were successfully produced using emulsification / solvent evaporation process. The microparticles yield from the three polymers was above 80% with no significance difference between the three polymers (p<0.05). The microparticles using the three EUDRAGIT® polymers were capable of encapsulating celecoxib at high efficiency. The highest encapsulation efficiency was for EUDRAGIT® S100 followed by the other two polymers with no real difference between the three polymers. The high encapsulation efficiency and microparticle yield suggested that the process is efficient and economical at this scale. The prepared microparticles of the drug (F3, F6) reduced the inflammation and damage to the colon. This reduction was more when compared to that of the drug suspension and F9.The reduction of colon inflammation induced by acetic acid was really clear with EUDRAGIT® S100 and EUDRAGIT® L100-55 and to lesser extent EUDRAGIT® L100. Celecoxib reduced the severity of colonic injury induced by acetic acid and the prepared microparticles increased and localized the drug effect on the colon. The used LC MS/MS assay was specific and accurate to determine Celecoxib in rat plasma. The results obtained from the pharmacokinetic analysis suggested that the delay in Tmax indicated delayed release and slow release of the drug from the microparticles leading to the localization of the drug at the site of action which is the colon and may affect the extent of drug absorption. There was a clear increase in the bioavailability of celecoxib prepared as microparticles using the three EUDRAGIT® polymers