Effect of Sodium Alginate Type on Drug Release from Chitosan-Sodium Alginate–Based In Situ Film-Forming Tablets

Natural polymers are promising as the carrier of matrix-based sustained release tablets but limited by their diversity in source and structure properties. Our previous studies found that chitosan (CS)- and alginate (SA)-based tablets can form self-assembled polyelectrolyte complex (PEC) film on the surface, which controlled drug release with a novel mechanism. To elucidate whether PEC-based sustained drug delivery system could weaken the influence of single-matrix material diversity on drug release behavior, taking theophylline as a drug model, the effect of SA structure properties, including viscosity, G/M ratio, SA salt type, and degree of esterification on drug release profiles, swelling, and erosion of CS-SA composite system was investigated. The results showed that the viscosity, G content, salt type, and esterification degree of SA had a remarkable influence on drug release when SA alone was used as a matrix, but little effect of these parameters on drug release was observed in CS-SA combination system. SA of low viscosity is superior in controlling drug release from CS-SA combination system. Potassium, magnesium salt of SA, and esterified SA can help form PEC of higher thickness with different swelling and erosion extent. In conclusion, this study demonstrated that drug release diversity due to SA structure difference can be well eradicated by using CS-SA combination system, which is a promising strategy to manufacture natural polymer-based products with constant quality.