Development and investigation of Niosomes of Brimonidine tartrate and Timolol maleate for the treatment of glaucoma

Due to the drawback of conventional therapy for ocular delivery like poor bioavailability of drugs due to tear production, non productive absorption, transient residence time, impermeability of corneal epithelium. These problems can be minimized by the application of niosomal vesicular system as well as combination of drugs provides the additive effect on reduction of IOP. The aim of the present study was to develop niosomal combination formulation of timolol maleate and brimonidine tartrate for the treatment of glaucoma. Niosomal formulations of brimonidine tartrate and timolol maleate were prepared by film hydration method. Span 60 and cholesterol used as an excipient. White rabbits of both sexes, weighing between 2 to 3 kg were used for the study. The prepared vesicles were evaluated for photomicroscopic characteristics, entrapment efficiency, in vitro, exin vitro drug release, in vivo intra ocular pressure lowering activity. Methods employed for the preparation of vesicles were found to be simple and reproducible, produced vesicles of acceptable shape and size with unimodal frequency distribution pattern. The in vitro, ex-in vitro drug release studies showed that there was a slow and prolonged release of drug which followed zero order kinetics. The intra ocular pressure lowering activity of prepared formulations were determined and compared with pure drug solution. It was found that intra ocular pressure lowering action was sustained for longer period of time which provides additive effect with combination. Stability study data revealed that the formulations were found to be stable when stored at refrigerator temperature (2 °C to 8 °C) and at 25 °C with no change in shape and drug content. Results of the study indicated that it is possible to develop a safe and physiological effective topical niosomal formulation which is patient compliance. IOP lowering activity of the combination of timolol maleate and brimonidine tartrate in niosomes was better as compared to alone medication, which shows the additive effect of combination medication.