The impact of viscosity on the dissolution of naproxen immediate-release tablets

The increase in viscosity of gastric fluid as a result of food ingestion is one criterion that can negatively impact the dissolution and solubility of orally administered medications. Consequently, it is crucial to address this issue in the pharmacokinetic profile assessment of oral formulations. In this scientific work, various kinds of viscosity enhancers, namely carboxy methylcellulose, pectin, guar gum, and xanthan, were applied to the preparation of different media similar to the biological condition after a meal, and their impacts on the rate of naproxen dissolution and its saturation solubility were evaluated.

A Brookfield viscometer was used to assess the rheological features of two potencies of each viscosity booster dissolved in fed state simulated intestinal fluid (FeSSIF). After 24 h of samples shaking, the saturation solubility of the selected medicine in the assessed media was measured using an ultraviolet spectrophotometer, and investigation of the drug dissolution profile was performed with a paddle dissolution apparatus in 200 mL of fluid.

Great reduction in the saturation solubility of naproxen was detected when the viscosity of the tested media was increased and the highest reduction of solubility was observed with pectin in FeSSIF. Similarly, the dissolution profile of naproxen decrease with enhancement of the viscosity of investigated media.

A polymer structure not only enhances the viscosity of media but also interferes with drug solubilization. As a result, it is essential to address the rheological aspect in designing in vitro media during the assessment of drug dissolution profiles.