In previous work, the use of psyllium huskas the main component of sustained release
preparations, was investigated. Granules of Metformin HCl containing different hydrocolloids
namely; psyllium Husk and sodium carboxy-methyl cellulose (Na CMC), “System I”, and
granules of sodium salicylate containing these hydrocolloids in addition to stearic acid, “System
II’ were prepared. In vitro release studies in phosphate buffer solution (pH 6.8) clearly revealed
the superiority of psyllium husk and Na CMCcombination in sustaining the release of both drugs.
The introduction of stearic acid in formulations SC5 and SP5 have, significantly, slowed down
the release of Sodium salicylate to 46% and 53%, respectively, after 7 hours. Mathematical
modeling of the release data revealed that the release mechanism which describes the diffusion of
both drugs from these systems is driven by a complex behavior such as swelling, matrix erosion
as well as diffusion through the swollen matrix of most formulations. Evaluation of the drug
release mechanism from these systems suggested that the release could be described by a
complex mechanism, which may involve First-order kinetics, Higuchi diffusion controlled as
well as Korsmeyer Peppas models.
Keywords:Release mechanism, granules, metformin, Psyllium husk, stearic acid

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