Thermo-sensitive gel in glaucoma therapy for enhanced bioavailability:In vitrocharacterization,in vivopharmacokinetics and pharmacodynamics study

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Aims:Glaucoma is a chronic ophthalmic disease, which has become one of the leading causes to progressive and irreversible blindness. Current ophthalmic drug delivery to treat glaucoma is mostly eyedrop, whose rapid elimination on corneal surface can lead to poor bioavailability. The present study was aimed to develop a timolol maleate loaded thermo-sensitive gel (TM-TSG) with improved bioavailability to treat glaucoma.Main methods:TM-TSG was prepared by homogeneously dispersing 0.3% (w/v) timolol maleate, 24.25% (w/v) poloxamer 407 (P407) and 1.56% (w/v) poloxamer 188 (P188) into phosphate buffer solution (pH=7.4) and the formulated TM-TSG was characterized.Key findings:TM-TSG was stored in liquid form at room temperature (25°C) and transited to semisolid gel at physiological temperature (32°C). The rheological property of TM-TSG was in favor of uniform distribution of drug. TM-TSG showed good stability at different conditions including centrifugation, autoclaving and different temperature. In vivo pharmacokinetic studies indicated that TM-TSG could enhance absorption of TM in aqueous humor and improve the ocular bioavailability in comparison of commercial TM eyedrops. In vivo experiment result showed that TM-TSG had greater effect in treating glaucoma than TM eyedrops by sustainably lowering intraocular pressure (IOP) for a week. Moreover, slit lamp test and histopathological analysis demonstrated that TM-TSG had excellent biocompatibility.Significance:TM-TSG could be a promising ophthalmic delivery system for glaucoma therapy.HIGHLIGHTSThe liquid-solid phase transition of thermo-sensitive gel facilitates administration and prolongs the drug retention time.Enhanced bioavailability is achieved by the prolonged retention and drug release compared with TM commercial eyedrops.

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