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The purpose of our study was to realize some pharmaceutical forms with extended release of Metoprolol, included in hydrophilic metocel or carbopol media (10%, 20% and 30% hydrophilic polymer), and to test the kinetic of Metoprolol release of these formulations in two distinct phases: 60 minutes in hydrochloric acid 0.1 N (simulating the gastric environment), and four hours in phosphate buffer solution pH 6.8 (simulating the intestinal environment). From the obtained data, it was found that for metocel forms the rate of Metoprolol release was much lower than the carbopol forms. It is well known that the kinetics of drug release from hydrophilic matrix is controlled by diffusion, as long as the hydrated polymer remains intact. Therefore, we found a linear relationship between the quantity of released drug and time's square root, which shows that Higuchi's equations, valid for explaining the release from insoluble matrix, can by also applied to hydrophilic matrix. [ABSTRACT FROM AUTHOR]