Controlled-release polymeric drug devices

Details are given of pilocarpine trapped in a matrix diffusion-controlled drug delivery system using hydrophilic inserts of polyhydroxyethyl methacrylate. The physical and chemical properties of pilocarpine were investigated to determine the mechanism of drug-polymer interaction and the effect of drug release behaviour of controlled release polymeric devices. 22 refs. 

This contribution will provide a review of polylectrolytes as biomaterials, with emphasis on recent developments. The first section will provide an overview of methods of synthesizing polyelectrolytes in the structures that are most commonly employed for biomedical applications linear polymers, crosslinked networks, and polymer grafts. In the remaining sections, the salient features of polyelectrolyte thermodynamics and the applications of polyelectrolytes for dental adhesives and restoratives, controlled release devices, polymeric drugs, prodrugs, or adjuvants, and biocompatibilizers will be discussed. These topics have been reviewed in the past, therefore previous reviews are cited and only the recent developments are considered here. 

In polymeric membrane and matrix-based micropumps, the membrane or the matrix makes the essential component of the delivery device that controls the rate of release. In matrix controlled delivery, the rate of the hydrolytic breakdown of the matrix is the governing process. In polymeric membrane-controlled release, the rate of hydration of the membrane and the subsequent diffusion of drug are the rate-controlling steps. 

Soppimath, K. S., T. M. Aminabhavi, et al. (2001). Biodegradable polymeric nanoparticles as drug delivery devices. J Control Release 70(1-2) 1-20. 

The driving force for drag release from a pump is a pressure difference that causes the bulk flow of a drag, or drug solution, from the device at a controlled rate. This is in contrast to the polymeric controlled release systems described above, where the driving force is due to the concentration difference of the drag between the formulation and the surrounding environment. Pressure differences in an implantable pump can be created by osmotic or mechanical action, as described below. 

Chien, Y. Mares, S. Berg, J. Huber, S. Lambert, H. King, K. Controlled drug release from polymeric delivery devices. Ill in vitro-in vivo correlation of intravaginal release of ethynodiol diacetate from sihcone devices in rabbits. J. Pharm. Sci. 1975, 64, 1776. 

DP method utilizes ink-jet printing technology to create a solid object by printing a binder into selected areas of sequentially deposited layers of powder. The active agent can be embedded into the device either as dispersion along the polymeric matrix or as discrete units in the matrix structure. The drug release mechanism can be tailored for a variety of requirements such as controlled release by a proper selection of polymer material and binder material. 

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