Natural Polymers in Sustained and Modified Release Matrix Tablets: A Comprehensive Review

AbstractThe development of sustained and modified release dosage forms is an important approach for maintainingtherapeutic drug concentrations, reducing dosing frequency and improving patient convenience. Naturalpolymers have attracted considerable interest as matrix-forming and release-modifying materials because oftheir biodegradability, biocompatibility, availability and functional versatility. This review discusses the roleof natural polymers in sustained and modified release matrix tablets, with emphasis on polymers obtained fromplant, animal, marine and microbial sources. Important materials including cellulose, starch, pectin, guar gum,karaya gum, chitosan, alginate, carrageenans, gelatin, xanthan gum, dextran and microbial glycans areconsidered in relation to their structural characteristics and pharmaceutical applications. The principalmechanisms by which natural polymer matrices regulate drug release—hydration, swelling, gel formation,diffusion, polymer relaxation and erosion—are described. The influence of polymer concentration, viscosity,particle characteristics, drug solubility, matrix porosity, gastrointestinal conditions and polymer modificationon release behavior is also discussed. Natural polymers can provide mucoadhesion, site-specific delivery,gastroretention and colon targeting in addition to conventional sustained release. However, variability insource, composition, purity, microbial quality and batch-to-batch performance remains an important challenge.Appropriate standardization, controlled processing and rational polymer combinations are therefore necessaryfor reproducible formulations. Overall, natural polymers represent versatile and sustainable platforms fordesigning matrix tablets and other modified drug delivery systems, particularly when their physicochemicalproperties are carefully characterized and matched with the therapeutic objective.