Impact of Simulated Gastrointestinal Fluid: Viscosity, Surface Tension, and pH on the Dissolution and Rheology Assessment of Viscosity of Two Commercial Candesartan Cilexetil Products.

Objectives: The aim of this study was to ivnestigate the effect of simulated gastrointestinal viscosity, surface tension, and pH on the dissolution rate of two commercial candesartan cilexetil (CC) products.

Materials and methods: In vitro dissolution of two commercial CC products and immediate release of 16 mg of CC were applied under two conditions: (1) the requirements of the United States Pharmacopeia (USP) and (2) conditions physiologically related to the gastrointestinal tract mimicking viscous food intake. The solubility of CC in different simulation fluids was also measured. The dissolution media's viscosity, surface tension, and pH were also measured. The viscosity of the gel layer was measured during CC dissolution.

Results: The CC dissolution rate was highest in the USP medium. It was found that the media type affected CC dissolution. The non-USP media exhibited a slower dissolution rate than the USP specification. The highest viscosity media lowered the dissolution rate in one of the CC products. Acidic pH showed a significant decrease in dissolution for both CC products. The solubility of CC was affected by solvent type (p value < 0.001).

Conclusion: Higher viscosity media slow the dissolution rate of a product, where a gel layer forms on the tablet surface.The results show variation in the dissolution media. This may reveal differences in the dissolution rates of the same drug in different products and media. Considering, viscosity's effect on dissolution might improve patient outcomes when treated with different products.