Possibility of a patch system as a new oral delivery system.

A new oral patch system has been designed to increase the residence time of model drugs within the gastrointestinal tract. The system consisted of three layers (1) water-insoluble backing layer (2) drug-carrying adhesive layer composed of a model drug, fluorescein (FL) or fluorescein isothiocyanate-dextran (FD), and gel-forming polymer and (3) pH-sensitive enteric polymer. These three layers system was prepared as 3.0 mm diameter patches. As references, tablet containing FL or FD was prepared. In vitro dissolution studies showed that the mean dissolution time (MDT) of model drugs from patch preparation was 0.739+/-0.021 h for FL and 0.407+/-0.021 h for FD, which were longer than from tablet, 0.327+/-0.008 h for FL and 0.270+/-0.019 h for FD. The two test preparations were orally administered to beagle dogs in a crossover manner at a FL dose of 30 mg/dog and the measured plasma FL concentrations were used for pharmacokinetic analysis. With FL patch preparation, area under the plasma drug concentration vs. time curve (AUC) was 2.12+/-0.24 microgh/ml and mean residence time (MRT) was 4.60+/-0.18 h, which were greater than those of tablet, AUC was 1.52+/-0.16 microgh/ml and MRT was 3.18+/-0.09 h, respectively. Oral patch preparation also increased both AUC and MRT of FD, a model macromolecular drug, which was formulated into both patches and tablets and administered to dogs (30 mg/dog). The AUC and MRT of FD from the patch preparation were 1.11+/-0.13 microgh/ml and 5.58+/-0.55 h and from tablets were 0.53+/-0.08 microg h/ml and 4.09+/-0.29 h, respectively. These results suggest that oral patch preparation has as a potential a new oral delivery system to obtain a long residence time of drug in the gastrointestinal tract.