Sustained-release drag delivery systems

Chiao, C.S.L. and Robinson, J.R. (1995) Sustained-release drag delivery systems. In Gennaro, A.R. (ed.) Remington the science and practice of pharmacy, vol. II. Mack Publishing Company, Easton, PA, pp. 1660-1675. 

Sustained and Controlled Release Drag Delivery Systems, edited by Joseph... 

Rajamma, A., Yogesha, H., Sateesha, S., 2012. Natural gums as sustained release carriers development of gastroretentive drag delivery system of ziprasidone HCl. DARU J. Pharm. Sci. 20, 58. 

In addition to the treatment of diseases of the lymphatics, drag targeting to the lymphatics may be used to facilitate sustained release effects, as the drag must distribute from the lymphatics into the general circulation. Delivery into the systemic circulation following oral lymphatic delivery is also a means of avoiding first-pass liver metabolism. 

Suspensions are commonly formulated by dispersing micronized drag powder (< 10 pm in diameter) in a suitable aqueous vehicle. Ophthalmic suspensions, particularly for the steroids, are thought to be acceptable as delivery systems since it is assumed that drag particles persist in the conjunctival sac giving rise to a sustained release effect. However, suspensions have a disadvantage that the concentration of dissolved drags cannot be manipulated due to their relative insolubility in the vehicle. 

Chhablani et al. showed that in oxidized PSi covalently loaded daunorubicin demonstrated sustained intravitreal release for 3 months without any evidence of toxicity, while physisorbed daunorubicin was released within 2 weeks and localized retinal toxicity were observed due to high daunorubicin concentration. Wu et al. added a new functionality to PSi dmg delivery system (Wu et al. 2011). They used 1-dimensional porous silicon photonic crystal in intravitreal delivery. The reflectance spectrum of the crystal (i.e., color) changed from red to green as daunombicin was releasing enabling real-time monitoring of the drag release proeess. These types of multifunctional delivery systems based on versatile properties of PSi are expeeted to be published much more in future. 

The rate of liposome accumulation in alveolar type-II cells is dependent on lipid composition. It is therefore possible to select liposome compositions displaying minimal interaction with these cells and thereby function as controlled-release systems for entrapped solutes. For example, liposomes composed of dipalmitoylphosphatidylcholine and cholesterol and containing entrapped sodium cromoglycate will provide sustained delivery of the drag for over 24 hours. Conversely other liposome compositions could be utilized for enhanced epithelial interaction and transport of the drug (e g. cationic lipids for the cellular delivery of the CFTR gene). 

As the majority of the posterior segment disorders are chronic in nature, sustained delivery of medications is highly desirable. Liposomes and microparticulates are such systems designed to release the encapsulated drag gradually and over an extended period of time. 

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