Pectin microspheres as ophthalmic carriers for piroxicam: evaluation in vitro and in vivo in albino rabbits

Microparticulate polymeric delivery systems have been suggested as a possib le approach to improve the low bioavailability characteristics shown by sta ndard ophthalmic vehicles (collyria). Purpose of this study was the evaluat ion of pectin microspheres as delivery system for piroxicam (Px). The micro spheres were prepared by a spray-drying technique; their morphological char acteristics were investigated by scanning electron microscopy (SEM), and th eir in vitro release behavior was evaluated in pH 7.0 USP buffer using a fl ow-through apparatus. Pr loaded in the pectin microspheres showed a faster in vitro dissolution rate with respect to solid micronized drug. The precor neal retention of fluorescein-loaded microspheres was evaluated in vivo in albino rabbits: an aqueous dispersion of fluorescent microspheres showed a significantly increased residence time in the eye (2.5 vs. 0.5 h) when comp ared with a fluorescein solution. In vivo tests in rabbits of dispersions o f Pr-loaded microspheres also indicated a significant improvement of Pr bio availability in the aqueous humour (2.5-fold) when compared with commercial Pr eyedrops. The potential advantages and limitations of this delivery sys tem are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.