The purpose of this study was to develop a poloxamer analogs/bioadhesive polymers-based in situ gelling ophthalmic delivery system aiming at enhancing bioavailability and anticataract effect. The effect of poloxamer 407 (P407), poloxamer 188 (P188), carbopol 934P (C934), and sodium hyaluronate (NaHA) concentration on the gelation temperature (GT) was examined. The GT of P407 based in situ gel increased with an increase in the P188 concentration. NaHA and C934 lowered the GT of poloxamer analogs based in situ gel. Correlation analysis demonstrated that in vitro drug release from in situ gel was controlled by gel dissolution and followed zero-order kinetics. Tiopronin in vitro transcorneal transit accorded with zero-order kinetics. Twenty-two percent P407 and 6% P188 containing 0.2% NaHA based formulation can be chosen as in situ gel matrix of tiopronin because of proper GT and sustained releasing ability. In vivo study showed that the area under the aqueous humor-concentration time curve of tiopronin increased by 1.6 folds for in situ gel, compared with tiopronin aqueous solution. High-dose tiopronin in situ gel and solution delayed the development of selenite cataract 6 d and 4 cl, respectively. The results showed that tiopronin in situ gel exhibits higher bioavailability and therapeutical effect. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 775-783, 2009