INTESTINAL TRANSIT OF BIOADHESIVE MICROSPHERES IN AN INSITU LOOP IN THE RAT - A COMPARATIVE-STUDY WITH COPOLYMERS AND BLENDS BASED ON POLY(ACRYLIC ACID)

Two commercially available copolymers of acrylic acid, Carbomer (Carbopol® 934P) and Polycarbophil (Carbopol® EX-55 resin), and blends with Eudragit® RL 100 were screened for their mucoadhesive properties by determining the force needed to detach a polymer coated glass plate from porcine intestinal mucosa in vitro. Microspheres of poly(2-hydroxyethyl methacrylate) (PHEMA) were synthesized by suspension polymerization and coated with candidate mucoadhesive polymers in an air-suspension process. A chronically isolated ileal loop model in the rat was used in order to study the intestinal transit of the microspheres. Bioadhesive properties of this potential drug delivery system were evaluated by recording the mean residence time of the microspheres when injected into the in situ perfused gut segment. Polycarbophil showed significantly improved mucoadhesive properties in vitro in comparison to Carbomer. In the in situ model, the residence time of Carbomer-coated microspheres was comparable to the non-coated controls, whereas Polycarbophil-coated spheres initially showed a marked bioadhesion. © 1990.