Controlled Drug Delivery and Ophthalmic Applications

Controlled drug delivery occurs when a polymer is combined with a drug in a such a way that the release profile is predefined. Conventional forms of drug delivery are based on tablets, eye drops, ointments and intravenous solutions. These delivery systems were characterized by an immediate and non controlled kinetics depending essentially on the properties of tissues to absorb drugs.In the last decades drug delivery devices have moved to more complex controlled systems. Advances in polymer science have led to the development of second generation drug-delivery systems which purpose is to maintain drug concentration in the blood or in target tissues at a desired value and during an extended period of time. The improvements in the properties of polymers, by combining different compounds and additives, the use of biodegradable polymers and the enhancement of diffusion processes come at the expense of more complex transport phenomena which are known to influence drug delivery rates. The urgency for mathematical models in the area and the necessity for a predictive environment, avoiding costly in vitro experiments, become all the more relevant in light of the heightened focus on polymer-based drug-delivery devices. Also future drug delivery modelling work should consider drug transport in target tissues after its release from polymeric devices. Efficient drug delivery to the eye is becoming increasingly vital with the development of new devices and the increasing prevalence of eye diseases, accompanying population ageing. In this paper we will present an overview of drug delivery from therapeutic lens to the anterior segment of the eye. The platforms we analyse and the models we present to simulate the drug release can be easily adapted to the case of transdermal drug delivery systems.