Influence of chitosan and its glutamate and hydrochloride salts on naproxen dissolution rate and permeation across Caco-2 cells

Chitosan and its glutamate and hydrochloride salts were evaluated for their efficacy in improving the dissolution behaviour of naproxen (a poorly water-soluble antiinflammatory drug) and its transport in vitro across Caco-2 cell monolayers. Drug-polymer physical mixtures and coground products, prepared at two different w/w ratios (30/70 and 10/90), were characterized by differential scanning calorimetry, X-ray powder diffractometry, scanning electron microscopy, and tested for dissolution properties. Coground systems were more effective than physical mixtures in improving drug dissolution and chitosan base, in spite of its lower water solubility, showed higher solubilizing power than its salts. According to the solid state analyses results, this effect was directly related to its stronger amorphizing power. Transport studies showed that only coground mixtures with chitosan glutamate salt allowed a significant drug apparent permeability improvement; however, they did not exhibit appreciable effects on the Caco-2 tight junctions (measured by the trans-epithelial electrical resistance variations), thus indicating that their enhancer effect was mainly due to an improved naproxen transport by transcellular passive diffusion rather than through the paracellular route. The direct compression properties and antiulcerogenic activity together with the demonstrated dissolution and permeation enhancer abilities toward naproxen make chitosan glutamate an optimal carrier for developing fast-action oral solid dosage forms of this drug.