Sodium alginate and alginic acid as pharmaceutical excipients for tablet formulation: Structure-function relationship

Alginic acid and its sodium salt are well-accepted pharmaceutical excipients fulfilling several roles in the development of solid oral dosage forms. Although they have attractive advantages as safety, abundance, relatively low cost and biodegradability, these natural polysaccharides possess a high variability that may limit their use as excipients for tablet formulation. Thus, to obtain robust formulations and high-quality drug products with consistent performance a complete understanding of the structure-property relationship becomes necessary as the structure of alginates affects both, technological and biopharmaceutical properties. This review compiles the compaction studies carried out that relate the structure of alginates to their mechanical and dissolution performances. The different analytical methods used to determine the chemical composition, primary structure and molecular weight distribution, major factors affecting the behavior of alginates in direct compression, are also exposed. Finally, different strategies reported to improve the properties of alginic acid as direct compression excipient are discussed.

Automated summary

Alginic acid and its sodium salt are widely used pharmaceutical excipients in solid oral dosage forms, but their high variability requires a thorough understanding of the structure-property relationship to achieve high-quality and consistent drug products. Compaction studies have shown the relationship between the structure of alginates and their mechanical and dissolution performances, while different analytical methods help determine the major factors affecting the behavior of alginates in direct compression.Various strategies have been discussed to improve the properties of alginic acid as a direct compression excipient.