Development of multiple-unit colon-targeted drug delivery system by using alginate: in vitro and in vivo evaluation

Drug delivery systems to the colon are being actively investigated. However, it is difficult to ensure that an oral preparation disintegrates specifically in the human colon. In this study, a pH-and enzyme-controlled, colon-targeted tablets (PECCTT) was established by using outer pH-coated layer and inner alginate-coated compression layer. The influence of the amount of alginate and enteric coat thickness on drug release had been investigated and the formulation that contained 30% alginate in compression layer and 13% weight gain in pH-coated layer was proved to protect the drug release from stomach and small intestine, the lag time was 7.04 +/- 0.17 h, and 84.45 +/- 1.3% of prednisone was released at 12 h. The results of drug release behaviors and SEM study indicated that drug release mechanism of PECCTT was corrosion. Hybrid scanner combining SPECT and CT was employed to monitor Tc-99m-contained tablets in the human gastrointestinal tract (GIT) and to obtain the images of the disintegration process. The results showed that the tablet remained intact during its transit through the upper GIT, the anatomical site of disintegration was found to be the sigmoidal colon, and the disintegration of the tablet started at 8 h post-dose in the volunteer.