Regarding the addition of colloidal silicon dioxide to the tablets, the results are according to the previous reports in the literature. The addition of silicon dioxide improved the flowability properties of the blends (repose angle: 27.41 ± 1.08), increased the hardness of the tablets (9.23 ± 1.44 N) as well as the amount of drug released after 30 minutes (63.35 ± 4.50%) in comparison to the same formulation prepared without it (Formulation I; hardness: 6.75 ± 1.15 N; drug released: 33.69 ± 6.30). The decrease in the repose angle of the blend with colloidal silicon dioxide is according to previous reports in the literature 16,21. In addition, the increase in hardness and amount of drug released could be explained by the greater interaction between cellulose microcrystalline and colloidal silicon dioxide than between the lubricant and cellulose microcrystalline 24. Considering that the colloidal silicone dioxide and stearic acid are both smaller than microcrystalline cellulose, it can be
583
Latin American Journal of Pharmacy - 27 (4) - 2008
assumed that microcrystalline cellulose particles are preferentially coated by colloidal silicon dioxide. In order to demonstrate this stronger interaction between cellulose microcrystalline and colloidal silicon dioxide, we prepared tablets containing colloidal silicon dioxide and without lubricants. These tablets presented the highest hardness value (13.43 ± 0.85 N) and the highest amount of drug release after 30 min (84.22 ± 6.04), showing the great interaction forces between cellulose microcrystalline and colloidal silicon dioxide particles, increasing the drug release of ASA in comparison to its per- centage of dissolution from raw material crystals (66.79 ± 6.22 %), as previously commented.
Regarding the addition of colloidal silicon dioxide to the tablets, the results are according to the previous reports in the literature. The addition of silicon dioxide improved the flowability properties of the blends (repose angle: 27.41 ± 1.08), increased the hardness of the tablets (9.23 ± 1.44 N) as well as the amount of drug released after 30 minutes (63.35 ± 4.50%) in comparison to the same formulation prepared without it (Formulation I; hardness: 6.75 ± 1.15 N; drug released: 33.69 ± 6.30). The decrease in the repose angle of the blend with colloidal silicon dioxide is according to previous reports in the literature 16,21. In addition, the increase in hardness and amount of drug released could be explained by the greater interaction between cellulose microcrystalline and colloidal silicon dioxide than between the lubricant and cellulose microcrystalline 24. Considering that the colloidal silicone dioxide and stearic acid are both smaller than microcrystalline cellulose, it can be
583
Latin American Journal of Pharmacy - 27 (4) - 2008
assumed that microcrystalline cellulose particles are preferentially coated by colloidal silicon dioxide. In order to demonstrate this stronger interaction between cellulose microcrystalline and colloidal silicon dioxide, we prepared tablets containing colloidal silicon dioxide and without lubricants. These tablets presented the highest hardness value (13.43 ± 0.85 N) and the highest amount of drug release after 30 min (84.22 ± 6.04), showing the great interaction forces between cellulose microcrystalline and colloidal silicon dioxide particles, increasing the drug release of ASA in comparison to its per- centage of dissolution from raw material crystals (66.79 ± 6.22 %), as previously commented.
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