A floating-type oral dosage form for piroxicam based on hollow polycarbonate microspheres: in vitro and in vivo evaluation in rabbits

A floating type dosage form (FDF) of piroxicam in hollow polycarbonate (PC) microspheres capable of floating on simulated gastric and intestinal fluids was prepared by a solvent evaporation technique. Incorporation efficiencies of over 95% were achieved for the encapsulation. In vitro release of piroxicam from PC microspheres into simulated gastric fluid at 37°C showed no significant burst effect. The amount released increased with time for about 8 h after which very little was found to be released up to 24 h. In intestinal fluid, the release was faster and continuous and at high drug payloads, the cumulative release reached above 90% in about 8 h. In vivo evaluation of different dosage forms of piroxicam such as free drug, drug-encapsulated microspheres and microspheres along with a loading dose of free drug in rabbits showed multiple peaking in the plasma concentration-time curve suggesting enterohepatic recirculation of the drug. Pharmacokinetic analysis showed that the bioavailability from PC microspheres alone was about 1.4 times that of the free drug and it was about 4.8 times for the dosage form consisting of the microspheres plus the loading dose. The elimination half life was increased by about three times for the microsphere preparation alone and nearly about six times for the dosage form comprising of microspheres and a loading dose in comparison to the free drug. Data obtained in this study demonstrated that FDF of piroxicam in PC microspheres was capable of sustained delivery of the drug for longer periods with increased bioavailability