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  • Title: Accessibility of solid core tablet for dissolution in an asymmetric triple-layer matrix system.
    Author: Yang L, Fassihi R.
    Journal: J Pharm Pharmacol; 2003 Oct; 55(10):1331-7. PubMed ID: 14607013.
    Abstract:
    The importance of glassy matrix surface area to ensure constant drug release and the effect of barrier layer thickness on the duration of linear release in an asymmetric triple-layer tablet with zero-order release kinetics were investigated. Poly(ethylene oxide) of different molecular weights and hydroxypropylmethylcellulose K4M were the major polymeric constituents, and verapamil hydrochloride was used as a drug model. The contribution of diffusion and polymer relaxation towards drug release was evaluated based on drug release data using a non-linear regression analysis algorithm. The results demonstrated that application of barrier layers to the central core tablet enables polymer relaxation to be the predominant mechanism in controlling drug release and leads to the often desired zero-order release kinetics. The duration of linear release from the asymmetric triple-layer tablet depends on the barrier layer thickness and composition. It was further indicated that the magnitude of diffusion and polymer relaxation in controlling drug release is affected by the accessibility of the drug core tablet for dissolution, as well as the inherent swelling and erosion characteristics of the release rate-controlling polymer.
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