Ocular drug delivery mechanism

Robinson, J.R. Ocular drug delivery mechanism(s) of corneal drug transport and mucoad-hesive delivery systems. STP. Pharm. Sci. 5(12), 839-846 (1989)... 

K. Hosoya, V. H. Lee, and K. J. Kim. Roles of the conjunctiva in ocular drug delivery a review of conjunctival transport mechanisms and their regulation. Eur J Pharm Biopharm 60 227-240 (2005)... 

The most common drug delivery method for treating ocular disorders is topical administration, due to its convenience and safety. However, the anterior segment of the eye also has various protective mechanisms for maintaining visual functions. After instillation of an ophthalmic drug, most of it is rapidly eliminated from the precorneal area due to drainage by the nasolacrimal duct and dilution by the tear turnover (approximately 1 pL/min) [17,18]. In addition, there is a finite limit to the size of the dose that can be applied and tolerated by... 

Several types of CDD systems have been designed based on various mechanisms of drug release (Table I). These mechanisms are dependent on the required site of drug delivery, the physicochemical properties of the drug and also of the delivery vehicle (13), Modes of administration can be oral, sublingual, transdermal, rectal, intrauterine, ocular, or parenteral (intramuscular, peritoneal, and subcutaneous routes of injection). 

Enriquez de Salamanca, A., Diebold, Y., Calonge, M., Garcia-Vazquez, C., Callejo, S., Vila, A., and Alonso, M. J. (2006), Chitosan nanoparticles as a potential drug delivery system for the ocular surface Toxicity, uptake mechanism and in vivo tolerance, Invest. Ophthalmol. Vis. Sci., 47(4), 1416-1425. 

These combinations will open new directions for the improvement of ocular bioavailability, but they will also increase the complexity of the formulations, thus increasing the difficulties in understanding the mechanism of action of the drug delivery systems. 

Silicone hydrogel (Si-Hy) materials combine the benefits of silicone or siloxane derivates in terms of oxygen permeability and mechanical properties with those of hydrogels in terms of wettability and hidrophilicity. Such properties are critical when it comes to the application at the ocular surface in the form of contact lenses (CL) to correct visual dysfunctions, as bandage mechanism or as drug delivery devices. Nowadays, CL are used by over 100 million people worldwide. 

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