ELSEVIER Journal of Controlled Release 41 (1996) 157-162 journal of controlled release Permeability studies across poly(alkylene carbonate) membranes V.B. Pokharkar, S. Sivaram* Division of Polymer Chemistry, National Chemical Laboratory, Pane-411 008, India Accepted 6 December 1995 Abstract The maximum steady state flux, diffusion coefficients and solubilities of piroxicam, a water insoluble drug and theophylline, a water soluble drug in poly(alkylene carbonate)s of varying alkyl chain lengths were determined and compared with poly(lactide)s. The permeabilities were found to be profoundly affected by the nature of the permeant as well as the polymer properties. Comparative studies in terms of overall performance with other well known systems revealed that poly(alkylene carbonate)s were more permeable than glassy poly(lactide)s and thus show potential as carriers in polymeric drug delivery systems. Keywords: Poly(alkylene carbonate); Permeability coefficient; Diffusivity; Piroxicam; Theophylline I. Introduction Polymeric materials play an important role in controlling solute diffusion rates in drug delivery systems. Evaluation of model permeation studies using synthetic membranes elucidates the basic diffusion mechanism and allows optimization of drug delivery system design. Most of the membrane permeation studies have been conducted using silicone polymers [1-4]. However, in recent years greater attention has been devoted to the use of biodegradable and biocompatible polymers, especial- ly, for parenteral drug delivery systems which do not need the surgical removal of the depleted device. Various biodegradable polymers such as polyesters, polyanhydrides and polyorthoesters have been studied. However, the mechanism of drug permea- tion across membranes has been reported only in the *Corresponding author. case of polyesters, e.g. poly(lactide)s, poly- (glycolide)s and poly(e-caprolactone) [5]. Permeation of solute through a membrane is a complex phenomena determined by a combination of factors. Since Fickian diffusion is usually the gov- erning mechanism for membrane moderated con- trolled drug release devices, the solubility of drug in polymeric membranes is of great importance. There- fore, the lipophilicty or hydrophilicity of the polymer membrane plays a major role. In accordance with Fick's law of diffusion, a variation in drug solubility, resulting from a change in polymer lipophilicity will lead to a change in the concentration gradient across membrane resulting in the modification of drug permeation rate. In this paper, we report the permeabilities of medium molecular weight drugs across aliphatic polycarbonate, or, poly(alkylene carbonate) mem- branes. The objective of this study was to determine the basic permeability characteristics of the poly- (alkylene carbonate) membranes in water at 37°C and 0168-3659/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All rights reserved PII S0168-3659(96)01325-9