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Abstract
Approximately 90% of all ophthalmic drug formulations are now applied as eyedrops. Although eyedrops are convenient and well accepted by patients, about 95% of the drug contained in the drops is lost due to absorption through the conjunctiva or through the tear drainage. A major fraction of the drug eventually enters the bloodstream and may cause side effects. To reduce drug loss and side effects, it is proposed to encapsulate the ophthalmic drug formulations in liposomes and to disperse the drug-laden liposomes in the lens material. Upon insertion into the eye, the liposome-laden lens will slowly release the drug into the pre-lens (the film between the air and the lens) and the post-lens (the film between the cornea and the lens) tear films and thus provide drug delivery for extended periods of time. This paper focuses on dispersing dimyristoyl phosphatidylcholine (DMPC) liposomes in poly-2-hydroxyethyl methacrylate (p-HEMA) hydrogels, which are a common contact lens material. The results of this study show that the p-HEMA gels loaded with liposomes are transparent and that these gels release drugs for a period of about 8 days. Contact lenses made of particle-laden gels are expected to deliver drugs at therapeutic levels for a few days. The delivery rates can be tailored by controlling the particle and the drug loading.