Controlled Delivery Systems

The eye is unique in its therapeutic challenges. An efficient mechanism, that of tears and tear drainage, which quickly eliminates drug solution, makes topical delivery to the eye somewhat different from most other areas of the body [137]. Usually less than 10% of a topically applied dose is absorbed into the eye, leaving the rest of the dose to potentially absorb into the bloodstream [138], resulting in unwanted side effects. The goal of most controlled-delivery systems is to... 

JL Zingerman, JR Cardinal, RT Chern, J Holste, JB Williams, B Eckenhoff, JT Wright. The in vitro and in vivo performance of an osmotically controlled delivery system-IVOMEC SR Bolus . J Controlled Release 47 1-11, 1997. 

A pharmacotectonics concept was illustrated by researchers, in which drug-delivery systems were arranged spatially in tissues to shape concentration fields for potent agents. NGF-releasing implants placed within 1-2 mm of the treatment site enhanced the biological function of cellular targets, whereas identical implants placed mm from the target site of treatment produced no beneficial effect (Mahoney and Saltzman, 1999). Because of some limitations with controlled delivery systems, alternatives such as encapsulation of cells that secrete these factors are discussed in the next section. 

The possibility of controlling the morphology of the product is relevant, especially in the forms of bio-polymer preparations and controlled delivery systems. Polymeric microparticles, fibers, or three-dimensional networks can be produced by tuning the operating variables. 

An alternative production of a controlled delivery system can be performed either by adding the filler to the matrix-formation mixture or by sorption of the guest molecule in the... 

Digenis, G.A., et al. 1999. Novel vaginal controlled-delivery systems incorporating coprecipitates of nonoxynol-9. Pharmaceut Develop Tech 4 421. 

Pharmacokinetics and Pharmacodynamics in Controlled Delivery System Design 3... 

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