EVALUATION OF MUCOADHESIVE POLYMERS IN OCULAR DRUG DELIVERY .2. POLYMER-COATED VESICLES

Association of Carbopol 934P and Carbopol 1342 a hydrophobic modified Carbopol resin) with phospholipid vesicles was assessed by photon correlation spectroscopy and microelectrophoresis at pH 7.4 and 5. The precorneal clearance of the polymer-coated vesicles was compared to that of uncoated vesicles by lacrimal dacryoscintigraphy in the rabbit. The mucoadhesive polymer-coated vesicles demonstrated significantly enhanced precorneal retention compared to noncoated vesicles only at pH 5 (P < 0.005). The entrapment and subsequent release of tropicamide from Carbopol 1342-coated and uncoated liposomes were determined in vitro together with an in vivo evaluation of the vesicles formulated at the lower pH. Mucoadhesive polymer-coated vesicles failed to increase significantly the bioavailability of the entrapped tropicamide compared to uncoated vesicles and aqueous solution.