Design and in vitro characterization of small unilamellar niosomes as ophthalmic carrier of dorzolamide hydrochloride

The objective of this work was to formulate and characterize non-ionic surfactant vesicles (niosomes) as an ocular carrier of dorzolamide hydrochloride (Dorzo); one of the antiglaucoma drugs. Niosomes were prepared of Cholesterol (Chol) with sorbitan monoesters (Span 20, 40, 60) or sorbitan trioleate (Span 85) in a molar ratio of 40:150. Those prepared from Span 40 were selected for further investigation on the effect of addition of dicetylphosphate (DCP) and polyoxyethylene fatty acid esters (either Tween 20, 40 or 80). All The batches were prepared using mechanical shaking technique, followed by sonication and then characterized using Zetasizer, transmission electron microscopy (TEM), calculating percent drug entrapment efficiency and cumulative percent released. Z-average sizes of the niosomes were between 25.9 and 165.5 nm. All niosomal formulations showed negative zeta potential charge. Dorzo was successfully entrapped in all of the formulations with entrapment efficiencies ranging between 34.81% and 97.66%. With reference to release profiles, Dorzo-loaded niosomal formulations showed significant reduction in cumulative percent drug released than Dorzo solution. High entrapment efficiencies, biphasic prolonged release rate and small particles size highlight Dorzo-loaded niosomal preparations as a promising ophthalmic carrier to prolong the drug lowering effect on the intraocular pressure.