MICROSPHERES AND NANOPARTICLES USED IN OCULAR DELIVERY SYSTEMS

Microparticles and nanoparticles are colloidal drug carriers in the mi cro- and submicron range. These systems were developed to overcome sol ubility problems of poorly soluble drugs as well as for long acting in jectable depot formulations and specific drug targeting options. These carriers were also evaluated for ophthalmic drug delivery purposes ov er the past 15 years. The main objective for these systems was to impr ove the classical aqueous eye drop formulations which have major disad vantages like a rapid elimination of the drugs from the precorneal are a. Consequently, colloidal carrier suspensions were designed to combin e ophthalmic prolonged action with the ease of the application of liqu id eye drops. The review summarises the present manufacturing methods and the materials used for these delivery systems with respect to opht halmic purposes. The distribution and penetration pathways of the part iculate delivery systems are also described. The applications of drug- loaded particles are presented with focus on ophthalmic diseases like glaucoma, inflammations or infections of the eye. Accordingly, particu late carriers outlined in the review include systems loaded with piloc arpine, beta-blockers, hydrocortisone, amikacin, and miscellaneous dru gs. Finally, the biodegradation and toxicity of the carrier materials under evaluation are reviewed.