Polyanhydrides drug release kinetics

Whether in copolymers or blends, inhomogeneous erosion has a nontrivial effect on drug release kinetics as will be shown later. Leong et al. (1985) demonstrated that the pH of the degradation media also has a dramatic effect on the erosion rate, which increases with increasing pH. The acceleration of degradation of polyanhydrides with increase in pH is widely reported and has been used to speed up experiments (Shakesheff et al., 1994). 

The past two decades have produced a revival of interest in the synthesis of polyanhydrides for biomedical applications. These materials offer a unique combination of properties that includes hydrolytically labile backbone, hydrophobic bulk, and very flexible chemistry that can be combined with other functional groups to develop polymers with novel physical and chemical properties. This combination of properties leads to erosion kinetics that is primarily surface eroding and offers the potential to stabilize macromolecular drugs and extend release profiles from days to years. The microstructural characteristics and inhomogeneities of multi-component systems offer an additional dimension of drug release kinetics that can be exploited to tailor drug release profiles. 

Shen, E. Kipper, M.J. Dziadul, B. Lim, M.-K. Narasimhan, B. Mechanistic relationships between polymer micro structure and drug release kinetics in bioerodible polyanhydrides. J. Control. Release 2002, 82 (1), 115-125. 

The incorporation and release kinetics from polyanhydride matrices of a number of drugs have been studied. Representative examples of several of these are described below. 

The in vitro degradation and drug release of polyanhydride formulations is not necessarily equivalent to the in vivo kinetics. For information on the in vivo kinetics, the interested reader is referred to the recent review by Katti et al. (2002) and the review by Domb et al. (1997). 

E. S. Park, M. Maniar, and J.C. Shah, Biodegradable polyanhydride devices of cefazolin sodium, bupivacaine, and taxol for local drug delivery Preparation, and kinetics and mechanism of in vitro release,/. Control. Release Off. J. Control. Release Soc., 52 (1-2), 179-189,1998. 

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