For the treatment of eye conditions, conventional eye drops have three major disadvantages: they must be applied frequently; their ocular bioavailability is low (i.e. less than 5% of the administered active is absorbed or becomes available at the site of physiological activity); and, their use is often associated with high systemic exposure to actives. The common alternative option, ophthalmic inserts, achieve sustained drug delivery but suffer from other limitations: they are difficult to insert (especially for the elderly and others with visual impairment) and easy to misapply; they are easily expulsed from the eye; patient compliance is low (discomfort and blurring of vision, difficulty of insertion, need for removal at the end of their useful life); and, they are costly to manufacture. Researchers in the UK believe that biodegradable polymer nanoparticles show great promise as drug delivery devices for the eye. They have developed well-tolerated systems that combine the sustained release characteristics of inserts with the patient acceptability of conventional eye drops.
With the new systems, biodegradable polymers can be combined with drugs in such a way that the drug is released from the material into the eye in a predesigned manner. The release of drug can be constant or cyclic over a long period, or triggered by the environment or a chemical signal. At the end of its useful life, the drug delivering polymer can be broken down naturally by the body.
Dr. John Tsibouklis, an expert in biomaterials and drug delivery from the School of Pharmacy and Biomedical Sciences at the University of Portsmouth, UK, explained the new drug delivery systems to Nanowerk: "We have developed nanoparticle-based ocular formulations that can release actives over extended time scales (days). These are administered into the conjunctival cul-de-sac and, at the end of their useful life, disappear into the lachrymal fluid. Among other advantages, the materials are well tolerated and the rate of their bioerosion/dissolution can be controlled."
The new drug delivery systems are described in a paper, titled "Polymeric materials for ophthalmic drug delivery: trends and perspectives", published in the July 3, 2006 online edition of Journal of Materials Chemistry.
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By Michael Berger, Copyright 2006 Nanowerk LLC