COMPARATIVE STUDY OF OPHTHALMIC DRUG DELIVERY SYSTEMS OF MODERN AND TRADITIONAL MEDICINE

Abstract

Most ocular diseases are treated with topical application of solutions administered newlineas eye drops. These conventional dosage forms account for nearly 90% of the currently newlineaccessible marketed formulations. They are somewhat primitive and apart from solutions newlineinclude suspensions, emulsions, ointments and gels. The practical reasons for selecting newlinesolutions are the generally favorable cost advantage, the greater simplicity of formulation newlinedevelopment and production and acceptance by patients, despite a little blurring of vision newline(Fitzgerald and Wilson, 1994). newlineThe conventional dosage forms are not longer sufficient to fulfill the present day newlinerequirements of providing a constant rate delivery for a prolonged time. The time course newlineof drug released in the eye from a conventional dosage form allows a pulsed entry, newlineresulting in a series of peaks and valleys in drug concentrations. These are most likely to newlinerepresent periods of over and under dosing of varying lengths of time. The other problem newlineencountered with the topical delivery of ophthalmic drugs is the rapid pre-corneal loss newlinecaused by drainage and tear turn over. After instillation of an eye drop, typically less than newline5 % of the applied drug penetrated the cornea and reaches the intraocular tissues, while a newlinemajor fraction of the dose is often absorbed systemically via the conjunctiva and the newlinenasolacrimal duct (Lang, 1995).Frequent local instillations of ophthalmic drugs provide an unusually high drug and newlinepreservative concentration at epithelial surface. Consequently, ocular conditions are newlineaggravated by over treatment. Repeated applications can cause biochemical and newlinemechanical injuries as well as sensitivity reactions resulting in blephroconjunctivitis. newlineThe need to reduce the local and systemic side effects and improvements in ocular newlinebioavailability necessarily requires the use of controlled ocular delivery. newline