Drug release zero-order

Surface erosion not only leads to zero-order drug release from devices that maintain a constant surface area, but has other important consequences. Among these are the following (1) the rate of drug release is directly proportional to drug loading, (2) the lifetime... 

Sandwich or reservoir-type intravaginal ring (IVR) devices have been developed to obtain zero-order drug release. 

One approach to surface erodibility is to prepare a polymer that contains linkages that are stable in base but are very labile in acid. Because one such linkage is an ortho ester, poly(ortho esters) are currently under intensive development as monolithic devices for zero order drug release 1). 

When a water-insoluble drug such as hydrocortisone is physically dispersed in the polymer and the polymer fabricated into thin disks which are then placed in a buffer at pH 7.4, release kinetics shown in Fig. 1 are obtained. Clearly, this system exhibits excellent zero order drug release kinetics with concomitant linear rate of polymer weight loss. The simultaneous polymer erosion and drug release is a clear indication that erosion occurs at the surface of the device and that drug release is controlled by erosion of the polymer. 

Mockel, JJi., lippold, B.C., 1993. Zero-order drug release from hydrocolloid matrices. Pharmaceutical Research 10, 1066—1070. 

Irrespective of administration route, sustained-release profiles or even zero-order drug release profiles are often required of the active pharmaceutical ingredients, in order to maintain relatively consistent plasma concentrations. Biotextiles as DDSs achieve the required sustained-release characteristics mainly by virtue of the physico-chemical properties of polymers when the active ingredients are dissolved or dispersed within the matrices. This can also be accomplished because of their particular structure, for example when the fibers are employed as drug reservoirs in the core/shell. Most of the biotextiles mentioned are designed to achieve sustained drug delivery. 

Charaeterisation of the mechanism of drug release from these systems may be performed by consideration of the magnitude of the release exponent (a.98). When n = 0.5 drug relea.se has oeeurred by Fickian (Higuchi) diffusion. A release exponent value of 1.0 is indicative of Case 2 (zero-order) drug release whereas whenever 0.5drug release is anomalous. 

Yu DG, Li XY, Wang X, Chian W, Liao YZ, Li Y (2013) Zero-order drug release cellulose acetate nanofibers prepared using coaxial electrospinning. Cellulose 20(l) 379-389. 

---