It seems as though there are always some kind of technologies in the works to reduce or eliminate the need for eyedrop application. Several I've read about or been talked at about by excited inventors in the past year or so include a punctal plug that secretes drops, contact lenses used to deliver drugs, special glasses with a microchip and tiny jets aiming a stream of tiny drops at the eyes, and now this gel-to-drop drug delivery system. It will be interesting to see if any of these types of things ever really comes to fruition.
Sustained Ocular Drug Delivery from a Temperature and pH Triggered Novel In Situ Gel System.
Gupta H, Jain S, Mathur R, Mishra P, Mishra AK, Velpandian T.
Drug Deliv. 2007 Nov;14(8):507-15.
Various ocular diseases like glaucoma, conjunctivitis, and dry eye syndrome require frequent drug administration. Poor ocular bioavailability of drugs (< 1%) from conventional eye drops is due mainly to the precorneal loss factors that include rapid tear turnover, nonproductive absorption, transient residence time in the cul-de-sac, and the relative impermeability of the drugs to corneal epithelial membrane. These problems may be overcome by the use of in situ gel-forming systems that are instilled as drops into the eye and undergo a sol-gel transition in the cul-de-sac. Our present work describes the formulation and evaluation of an ocular delivery system of timolol maleate based on the concept of both temperature and pH-triggered in situ gelation. Pluronic F-127 (a thermosensitive polymer) in combination with chitosan (pH-sensitive polymer also acts as permeation enhancer) was used as gelling agent. The developed formulation was characterized for various in vitro parameters e.g., clarity, gelation temperature and pH, isotonicity, sterility, rheological behavior, drug release profile, transcorneal permeation profile, and ocular irritation. Developed formulation was clear, isotonic solution, that converted into gel at temperatures above 35 degrees C and pH 6.9-7.0. A significant higher drug transport across corneal membrane and increased ocular retention time was observed using the developed formulation. The developed system is a viable alternative to conventional eye drops for the treatment of glaucoma and various other ocular diseases.