DEVELOPMENT AND CHARACTERIZATION OF THEOPHYLLINE SUSTAINED-RELEASE MATRIX TABLETS USING NATURAL POLYMERS
Theophylline is a narrow-therapeutic-index bronchodilator whose short half-life necessitates frequent dosing, making it a strong candidate for sustained-release (SR) delivery. This study aimed to develop and characterise theophylline SR matrix tablets using natural, biodegradable polymers - guar gum, xanthan gum and hibiscus mucilage - as economical alternatives to synthetic release retardants. Methods: Six matrix formulations (F1-F6) were prepared by direct compression with increasing polymer loads. Preformulation (solubility, FTIR compatibility), powder micromeritics, post-compression quality attributes and in-vitro dissolution (USP apparatus II, 12 h) were evaluated, and release data were fitted to zeroorder, first-order, Higuchi and Korsmeyer-Peppas models. Results: The drug was freely soluble in phosphate buffer (1.05 mg/mL) and FTIR showed no drug-excipient incompatibility. Blends flowed acceptably (angle of repose 27.5-29.1 deg; Carr's index 21-23%). All tablets met pharmacopoeial limits for weight variation, hardness (4.6-5.4 kg), friability (<1%) and drug content (98.8-101.2%). Cumulative release at 12 h ranged from 72% (F1) to 98% (F6); retardation increased with polymer concentration. Release followed Higuchi diffusion with anomalous (non-Fickian) transport by the KorsmeyerPeppas model. Conclusion: Natural polymers effectively sustained theophylline release over 12 h, offering a cost-effective, biocompatible matrix platform; the higher-polymer formulations provided the most controlled release