Bilayer tablets of aceclofenac sodium were developed using carboxymethylated white\nyam (Dioscorea rotundata) starch (CWY) for a fast release layer (2.5, 5.0, and 7.5%\nw/w), and acid-hydrolyzed bitter yam (Dioscorea dumetorum) starch (ABY) for a sustaining\nlayer (27% w/w). Sodium starch glycolate (SSG) and hydroxypropyl methyl cellulose\n(HPMC) were used as standards. The starches were characterized using Fourier Transform\nInfrared spectroscopy (FT-IR), particle size, swelling power, densities and flow analyses.\nMechanical properties of the tablets were evaluated using crushing strength and friability\nwhile release properties were evaluated using disintegration and dissolution times.\nDistinctive fingerprint differences between the native and modified starches were revealed\nby FT-IR. Carboxymethylation produced starches of significantly (p < 0.05) higher swelling\nand flow properties while acid-modification produced starches of higher compressibility.\nBilayer tablets containing ABY had significantly higher crushing strength and lower\nfriability values (p < 0.05) than those containing HPMC. Crushing strength increased while\nfriability values decreased with increase in CWY. Generally tablets containing the modified\nDioscorea starches gave faster (p < 0.05) disintegration times and produced an initial\nburst release to provide the loading dose of the drug from the immediate-release layer\nfollowed by sustained release (300 Ã?± 7.56ââ?¬â??450 Ã?± 11.55 min). The correlation coefficient\n(R2) and chi-square (?2) test were employed as error analysis methods to determine the\nbest-fitting drug release kinetic equations. In vitro dissolution kinetics generally followed\nthe Higuchi and Hixson-Crowell models via a non-Fickian diffusion-controlled release.\nCarboxymethylated white yam starch and acid-modified bitter yam starch could serve as\ncheaper alternative excipients in bilayer tablet formulations for immediate and sustained\nrelease of drugs respectively, particularly where high mechanical strength is required.
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