由 Lynn Shapiro
, Writer | August 13, 2009
A new drug delivery system that uses a tiny silicone cup sealed to the outer surface of the eyeball may greatly improve the way doctors deliver medicine to people with eye diseases, says A. Linn Murphree, M.D., director of the Retinoblastoma Program in The Vision Center at Childrens Hospital, Los Angeles.
Dr. Murphree tells DOTmed News that the tiny cup isolates the medication targeted to the eye from being absorbed into the blood stream. This new delivery system is a safe and non-invasive way of delivering effective doses of medications to the interior of the eye over long periods of time, he says.
Dr. Murphree is especially interested in kids who have an eye cancer called retinoblastoma but he says the cup can be used to deliver drugs for any disease, including macular degeneration, glaucoma and diabetes.
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Eye Drops Ineffective
Currently, the drops used for retinoblastoma and the injections used for macular degeneration are risky and ineffective, he says.
"When we give injections, it's like taking a whole bucket of water and throwing it at a building. We're splashing medicine on the eye, except most of it is running off. He adds that eye drops are just as ineffective, because while most diseases that affect vision are in the back portion of the eye, eye drops can only reach the front of the eye. "Traditionally, we've always had a real problem getting enough medicine inside the eye. So, now we inject medicine into a vein in the eye, but that requires a lot of drug therapy and a lot of side effects," Dr. Murphree says.
Macular degeneration is a case in point. Macular degeneration medicine must be injected into the eye once a month. Shots in the eye can lead to hemorrhaging, retinal detachment, and infections, he says.
"In the past, there was no way of isolating the drug while it slowly diffused into the eye. But the cup isolates the drug from being carried away by the blood vessels around the eye, using a soft silicone that's sealed to the outside of the eye, Dr. Murphree explains.
He says that the silicone cup is first sealed to the eye and is then injected with liquid medication to treat the disease. The cup releases medicine slowly over days or weeks.
Retinoblastoma: Dr. Murphree's Passion
Dr. Murphree is passionate about helping children beat retinoblastoma. Currently, he says, the only way to treat this disease is to inject chemotherapy medication into an eye vein and hope it reaches the cancer cells in one or perhaps both eyes.
"We are giving 99 percent more chemo than is needed to make sure the medicine gets into the eye, but most of it is going into the bloodstream, causing nausea, reducing kids' white cell count, and depressing their immune systems," he says. "Because the drug delivered via the cup is being administered directly into the eye and not systemically, you're not giving more than you need, and you're getting 30 to 40 times more of the drug delivered to the cancer site than with an injection."