The Dry Eye Zone

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Abstract: Preocular residence time

All about trying to figure out how to make stuff stay on the eye longer - not just for lubricants, presumably, but for delivery of any ocular drug. They got these "mucoadhesive microdiscs" to stay up to an hour or so.

Mucoadhesive Microdiscs Engineered for Ophthalmic Drug Delivery: Effect of Particle Geometry and Formulation on Preocular Residence Time.Invest Ophthalmol Vis Sci. 2008 Aug 8. [Epub ahead of print]
Choy YB, Park JH, McCarey BE, Edelhauser HF, Prausnitz MR.

Purpose. To test the hypothesis that mucoadhesive microdiscs formulated in a rapidly dissolving tablet can increase preocular residence time.

Methods. Microparticles, smaller than 10 micro-m in diameter, were fabricated by emulsification with poly(lactic-co-glycolic acid) (PLG) as a core material and, in some cases, poly(ethylene glycol) (PEG) as a mucoadhesion promoter. To examine the effect of particle geometry, microparticles were also cut to possess flat surfaces (i.e., microdiscs) and compared with spherical particles (i.e., microspheres). In vitro mucoadhesion of microparticles was tested on a mucous layer under shear stress mimicking the human blink. The resulting microparticles were also formulated in two dosage forms - an aqueous suspension and dry tablet - to test the effect of formulation on the retention capacity of microparticles on the preocular space of rabbits in vivo.

Results. Mucoadhesive microdiscs adhered better to the simulated ocular surface than the other types of microparticles. When a dry tablet embedded with mucoadhesive microdiscs was administered in the cul-de-sac of the rabbit eye in vivo, these microdiscs exhibited longer retention than the other formulations tested in this work. More than 40% and 17% of mucoadhesive microdiscs remained on the preocular surface at 10 min and 30 min after administration, respectively. Fluorescence images from the eye surface showed that mucoadhesive microdiscs remain for at least 1 h in the lower fornix.

Conclusion. This study demonstrated that mucoadhesive microdiscs formulated in a dry tablet can achieve a prolonged residence time on the preocular surface and thus are a promising drug delivery system for ophthalmic applications.