Polymeric implants drug release

Polymeric membrane-based implantable drug delivery systems have been developed to deliver growth hormone, hormonal contraception, and leuprolide for the treatment of prostate cancer. Implanted sialic tubes loaded with lev-onorgestrel Norplant system) is used outside the United States to provide five years of sufficient sustained release of the... 

This book is a companion volume to Pharmaceutical Technology Controlled Drug Release, Volume 1, edited by M.H.Rubinstein and published in 1987. It focused on the different types of polymeric materials used in controlled release. This book extends these concepts to include drug properties, design and optimization, coating, the effect of food and pharmacokinetics. It also reflects the growing interest in biodegradable polymers in oral and topical formulations and the use of sterile implants. 

The Cypher sirolimus-eluting stent from Cordis uses a blend of poly(ethylene-co-vinyl acetate) (PEVA) and poly(n-butyl methacrylate) (PBMA) as the polymeric matrix for sirolimus release. Both PEVA and PBMA have individually been used as implants in humans and demonstrated excellent biocompatibility. The blend of PEVA and PBMA is physically mixed with sirolimus in a weight ratio of 2 1. In vivo studies have shown that the majority of the drug is released in a sustained fashion in 30 days with complete drug release in 90 days as... 

Redmon, M.P. Physicochemical Characteristics of a Porous Polymer Matrix for Drug Dehvery. Ph.D. thesis. University of Kentucky Lexington, KY, 1989. Brannon-Peppas, L. Design and mathematical analysis of controlled release from microsphere-containing polymeric implants. J. Contr. Rel. 1992, 20, 201-207. 

Brashear and coworkers developed a diffuse reflectance NIRS method to quantify lomefloxacin and polyethyleneglycol (PEG) within a polymeric implant. The properties of pore-forming excipients such as PEG are known to affect the rate of drug release from a matrix. 

Septicin antibacterial implant for the treatment of chronic bone infections have been developed [21-24]. The multidisciplinary concept of polymeric implants has expanded to include research on the chemistry and characterization of polymers, experimental and theoretical polymer degradation and drug release, toxicology and metabolism, and research in specific fields of applications such as cancer, proteins and hormones delivery, infectious diseases, and brain disorders. This chapter concentrates on the chemistry and characterization of polyanhydrides with a brief description on recent applications of polyanhydrides. 

Figure 1.1 Development of polymeric biomaterials for controlled delivery tissues. This book will consider several aspects of the development of delivery systems including the characterization of biocompatible polymers, methods for incorporating bioactive agents into polymer matrices and microspheres, and methods for quantitative analysis of kinetics of drug release. Since these devices are developed for the delivery of agents to tissues, a critical component in this analysis will be the consideration of drug transport through the local tissue surrounding the implant.

For implantable reservoir devices, a cylindrical geometry is often more practical than a planar arrangement. Consider a cylindrical reservoir surrounded by a polymeric membrane (Figure 9.2c) the cylinder has a length L, cross-sectional radius b, and wall thickness b — a.ln practice, the rate of drug release from this cylinder can be modified by changing the geometry of the device (by... 

A. Roos, D. Klee, K. Schuermann, and H. Hocker. Development of a temperature sensitive drug release system for polymeric implant devices. Biomaterials, 24(24) 4417 23, November 2003. 

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