ARLINGTON, Va., March 28, 2003 – Drug-primed contact lenses could deliver medicine more safely and effectively than eyedrops, researchers reported in New Orleans this week.

At the national meeting of the American Chemical Society, researchers described a process for manufacturing soft contact lenses containing timed-release capsules for drug delivery. The medicine is encapsulated in oil-based nanoparticles so small they are invisible to the eye and will not cloud the lenses.

The researchers from the University of Florida found that these drug-primed lenses can deliver therapeutic doses for about five days. The delivery rate can be controlled by altering the size, concentration, and structure of the nanoparticles.

Eye drops are commonly used for such diseases as glaucoma, but 95 percent of drops are washed away by tears, which drain into the nasal cavity and from there can enter the bloodstream and cause side effects. The glaucoma drug Timolol, for example, can cause heart problems.

Anuj Chauhan, Ph.D., of the Department of Chemical Engineering and graduate student Derya Gulsen experimented with a large sample of the hydrogel used to make soft contact lenses. They placed the anesthetic Lidocaine inside nanoparticles and incorporated them into the microstructure of the hydrogel, then placed the hydrogel in a solution in a lab dish. The Lidocaine diffused from the contact lens material into the surrounding solution at a rate consistent with effective drug delivery.

In a contact lens, the drug would seep out slowly into the thin area between the lens and the surface of the eye, where tears could not wash it away.

"Due to the slow diffusion, drug-laden contact lenses can provide continuous drug release for extended periods of time," the researchers said.

Their next step is to achieve consistent delivery at different rates and then, if successful, move on to animal and human trials.

The idea of delivering drugs through contact lenses dates back to the 1970s, but the research has not produced a clinical application. Chauhan has filed for a patent, but it may be many years before this type of technology is approved for patients.

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Anuj Chauhan