Ocular drug delivery system: Approaches to improve ocular bioavailability

Ocular drug delivery system (ODDS) is one of the most challenging tasks faced by pharmaceutical researchers. For a prolonged duration the major barriers in ocular medication are the ability to maintain a therapeutic level of the drug at the site of action. The ophthalmic preparations are available as buffered, sterile and isotonic solution. For the ocular delivery of drugs, several types of dosage forms are prepared and marketed. As drops are easier to administer so the most prescribed dosage form is the eye drop solution. For prolonged therapeutic action ointment, suspensions and gelled systems are also used. Frequent dosing in case of eye drop is the main issue for this system. The new drug delivery systems for this type of delivery is ocuserts, which are designed to eliminate the frequent administration of the drug by releasing the drug at predetermined and predictable rates. For this system the bioerodible implantable elements having multiple layers of different materials with different concentrations of materials are used and this generally include controlled, delayed and or sustained released formulation. The elements generally include an inner layer, or core, including a therapeutic agent, and one or more outer layers made of polymeric materials and this system is also able to prolong the residence time.