Design, optimisation and evaluation of in situ gelling nanoemulsion formulations of brinzolamide.

The present research work summarises the development of an in situ gelling ophthalmic nanoemulsion of brinzolamide providing sustained release and prolonged therapeutic effect for the treatment of glaucoma. Nanoemulsions were prepared using castor oil, polyoxyl 35 castor oil and polysorbate 80 and with gellan gum as the in situ gelling agent. Formulations were screened based on globule size, Zeta potential, in vitro drug release and stability towards phase separation and sol to gel conversion upon storage. Selected formulations exhibiting a low mean globule diameter (< 160 nm), narrow size distribution (polydispersity index < 0.3), quick in vitro gelling time (< 15 s) and stability for at least 6 months at 25 °C/40% RH and 40 °C/25% RH were evaluated for intraocular pressure (IOP)-lowering efficacy studies using glaucomatous rabbits. Tested nanoemulsion formulations were well tolerated and significantly decreased IOP relative to saline and placebo controls (p < 0.005). Furthermore, an appreciable increase in the area under change in IOP from baseline (ΔIOP) vs. time curve and a longer mean residence time (MRT) was also observed for the test formulations compared with commercially available suspension of brinzolamide (Azopt, Alcon Laboratories, USA). Thus, nanoemulsion formulations containing in situ gelling polymer may serve as improved drug delivery system providing superior therapeutic efficacy and better patient compliance for the treatment of glaucoma. . Graphical abstract.