In this thesis, we observed and evaluated the release of diclofenac sodium (Na-DF) from matrix tablets in media with different viscosities and at different hydrodynamic conditions. We used 4x diluted Mcllvaine buffer pH 5 and pH 6.8 as media for diclofenac sodium release, to which a hydroxypropyl methylcellulose (HPMC) was added to increase medium viscosity. HPMC was selected based on a literature review where the viscosity of gastric contents after a meal was simulated by adding HPMC into the medium. In our experiments the polymer was added to the media in concentrations from 0% (w/V) to 1.4% (w/V). Instead of HPMC, we also added different concentrations of sodium chloride (NaCl) in some media. Dissolution tests were performed on an apparatus II at different speeds of paddle rotations and in a glass-bead flow-through system, thereby we assessed the effect of distinctive hydrodynamic or mechanical load on the tablets. The concentration of diclofenac sodium released from matrix tablets was calculated from absorbances measured with a UV-VIS spectrophotometer. During the dissolution experiments, we also observed the disintegration times of the tablet. Additionally, we also tested the disintegration time of the tablet on the disintegration tester apparatus.
From the dissolution experiments, we observed that the increased viscosity of the media impacts on the release, as Na-DF release was slower in more viscous media, at both pH medium pH values 6.8 and 5. Also, the tablets disintegrated more slowly in viscous media in dissolution tests as well as in a test performed on the disintegration tester apparatus. In comparison to the release of Na-DF in the media with pH 5 and pH 6.8, we observed that the release in media with pH 5 at certain concentrations HPMC was slower than at pH 6.8. Additionally, the tablet disintegration times were also slower at pH 5. From dissolution tests in media with NaCl, we observed that at particular NaCl concentrations, Na-DF release was slowed similarly as in media with added HPMC. In experiments where we studied the influence of hydrodynamic loads on Na-DF release in viscous media, the differences in Na-DF release in media with different viscosities were smaller at higher mechanical loads. We also observed that at higher media viscosities, the differences between the release profiles at different hydrodynamic loads are greater than at lower media viscosities.
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