Matrix tablets drug release from

This study indicates that drug release from these formulations is by a matrix-diffusion-controlled process. The release rate constant shows an inverse relationship with the concentration of carbomer only. For all the formulations, release rate constants were independent of tablet hardness. 

Drug release from controlled release matrix tablets has been described by many kinetic theories [20,21]. Fig. 4 illustrates the release profiles of the validated dissolution (experiments 12, 12b and 12c) and the release profiles obtained from fits to the Weibull, Higuchi and Hixson-Crowell models. Figs 5 and 6 show the curves after linear transformation. 

T. D. Reynolds, S. A. Mitchell, and K. M. Balwinski. Investigation of the effect of tablet surface area/volume on drug release from hydroxypropylmethylcellulose controlled-release matrix tablets. Drug Dev. Ind. Pharm. 28 457—466, 2002. 

Drug release from swellable matrix tablets is based on the glassy-rubbery transition of the polymer which occurs as a result of water penetration into the matrix. Therefore, the gel layer is physically delimited by the erosion (swollen matrix-solvent boundary) and swelling (glassy-rubbery polymer boundary) fronts. 

The mechanisms of drug release from dextran matrix occur in the early stage by polymer swelling, and the tablet thickness increases. Soon thereafter, polymer (and drug) dissolution starts occurring. The polymer dissolves because of chain disentanglement. Thus, there is a slow diminution of the thickness because of erosion until, finally, the tablet disappears (time > 480min). 

Huang, L-L., and Schwartz, J. B. (1995), Studies on drug release from a carbomer tablet matrix, Drug Dev. Ind. Pharm., 21,1487-1501. 

While the drug release from wax matrix tablets followed the square root of time relationship, approximately zero-order release of ephedrine hydrochloride and procaine hydrochloride could be obtained with multi-layered matrices of hydrogenated castor oil containing different concentrations of the active compound in each layer. 

Huang, H.-P. Mehta, S.C. Radebaugh, G.W. Fawzi, M.B. Mechanism of drug release from an acrylic polymer-wax matrix tablet. J. Pharm. Sci. 1994, 83, 795-797. 

Sungthongjeen S, Sriamornsak P, Pitaksuteepong T, et al. Effect of degree of esterification of pectin and calcium amount on drug release from pectin-based matrix tablets. AAPS Pharm Sci Tech... 

Jovanovic M, Jovicic G, Duvic Z, et al. Effect of fillers and lubricants on acetylsalicylic acid release kinetics from eudraglt matrix tablets. Drug Dev Ind Pharm 1997 23(6) 595-602. 

The mechanism of drug release from hydrophilic matrix tablets after ingestion is complex but it is based on diffusion of the drug through, and erosion of, the outer hydrated polymer on the surface of the matrix. Typically, when the matrix tablet is exposed to an aqueous solution or gastrointestinal fluids, the surface of the tablet is wetted and the polymer hydrates to form a gelly-like structure around the matrix, which is referred to as the gel layer . This process is also termed as the... 

The effect of compression force on drug release from hydrophilic matrices is minimal when tablets are made with sufficient strength and optimum levels of polymers are used [48]. One could relate variation in compression forces to a change in the porosity of the tablets. However, as the porosity of the hydrated matrix is independent of the initial porosity, the compression force is expected to have little influence on drug release rate [79], Once a sufficient tablet hardness suitable for processing and handling is achieved, tablet hardness would have little further effect on drug release profile. To ensure consistent porosity and avoid entrapment of air within the dry tablet core, a pre-compression step may have to be considered in the manufacture of matrices. 

Parojclc J, Duric Z, Jovanovic M, Ibric S. An investigation into the factors influencing drug release from hydrophilic matrix tablets based on novel carbomer polymers. Drug Deliv 2004 11 59-65. 

Water penetration is of utmost importance for drug release from hydrophilic films and from the so-called hydrophilic compressed matrix tablets [14, 75], In the former case, the drug is incorporated by solubilizing or suspending it in the polymer solution, which is subsequently dried off. In the latter situation, the drug is mixed with the polymer and the powder blend is compressed in a die at an adequate pressure. 

Alvarez, C. Torrado, J.J. Cadorniga, R. Stereoselective drug release from ketoprofen and ricobendazole matrix tablets. Chirality 1999, 11, 611-615. 

Borgquist, P., Kitchner, A., Piculell, L., Larsson, A., Axelsson, A., 2006. A model for the drug release from a polymer matrix tablet — effects of swelling and dissolution. Journal of Controlled Release 113, 216—225. 

Hydroxypropylmethyl cellulose Hydroxypropyhnethyl cellulose (HPMC) (Figure 28.2) is water-soluble cellulose ether and it can be used as hydrophilic polymer for the preparation of controlled-release tablets. Water penetrates the matrix and hydrates the polymer chains, which eventually disentangle from the matrix. Drug release from HPMC matrices follows two mechanisms, drug diffusion through the swelling gel layer and release by matrix erosion of the swollen layer. " ... 

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