Formulation and Evaluation of Controlled-Release Repaglinide Tablets Using Eudragit RS100 and Carbopol P974 NF Polymer Combinations

Abstract

Repaglinide is a short-acting insulin secretagogue whose short half-life necessitates frequent dosing, compromising adherence. Controlled-release (CR) matrix tablets combining hydrophobic and hydrophilic polymers can sustain drug release and reduce dosing frequency. To formulate and evaluate CR repaglinide tablets using Eudragit RS100 and Carbopol P974 NF at varying drug: polymer ratios, with and without natural co-excipients, and to characterise their physicochemical properties, in vitro release, and release kinetics. Nine formulations (CR-R1–CR-R9) were prepared by direct compression and wet granulation at drug: polymer ratios of 10:1, 10:2 and 10:3, with gum acacia and guar gum as co-excipients in selected batches. Pre-compression (Carr's index, Hausner's ratio, angle of repose) and post-compression (weight variation, thickness, hardness, friability, drug content) parameters were assessed per pharmacopeial standards. In vitro release was studied by USP Method I and modelled with the Power Law equation; similarity (f2) and difference (f1) factors were calculated against a reference product. Data were analysed by one-way ANOVA with Tukey's post hoc test. All blends showed excellent-to-very-good flow (Carr's index 9.22–11.88%; Hausner's ratio 1.06–1.16; angle of repose 29.99–31.94°). All tablets met pharmacopeial limits for weight variation, hardness (6.5–7.2 kg/cm 2 ), friability (<0.5%) and drug content (97.1–99.7%). Drug release at 2 hours ranged from 77.0% to 92.0%. Power Law fitting (r² = 0.988–0.997) indicated anomalous non-Fickian diffusion (n = 0.608–0.790) for all formulations. Eudragit RS100–Carbopol P974 NF matrices produced robust, pharmacopeia-compliant repaglinide CR tablets with diffusion/erosion-controlled release, supporting this polymer combination for sustained oral repaglinide delivery.