Bioadhesive microspheres .3. An in vivo transit and bioavailability study of drug-loaded alginate and poly(fumaric-co-sebacic anhydride) microspheres

Bioadhesive drug delivery systems (BDDSs) could improve bioavailability by protecting bioactive molecules from physical and chemical degradation, enhancing absorption rates by minimizing diffusion barriers, and increasing the period for absorption by prolonging residence time. The in vivo bioadhesive performance of calcium alginate microspheres and poly(fumaric-co-sebacic anhydride) 20:80 microspheres were evaluated in two ways. Firstly, effect on GI transit was measured in rats. P(FA:SA) 20:80 microspheres showed significantly prolonged retention in the gut when compared to alginate microspheres. Secondly, the ability of these polymers to improve relative bioavailability of a model drug, dicumarol, in rats was assayed. A significant increase was measured in the area under the plasma concentration-time curve for dicumarol encapsulated in P(FA:SA) 20:80 when compared to its controls. The results of this study suggest that polymers which have bioadhesive forces in vitro and delayed GI transit in vivo may be used to improve oral bioavailability of certain drugs. (C) 1997 Elsevier Science B.V.