Effects of modification and incorporation techniques on disintegrant properties of wheat (Triticum aestivum) starch in metronidazole tablet formulations.

BACKGROUND Natural polymers serve as cheap, non-toxic, biocompatible excipients in drug delivery. OBJECTIVES Starch from wheat (Triticum aestivum) was investigated as a disintegrant in metronidazole tablet formulations in comparison with sodium starch glycolate (SSG), a standard, synthetic but relatively more expensive disintegrant. MATERIAL AND METHODS Native wheat starch (NAS) was modified by pregelatinization (PGS) and microwave irradiation (MCW). The starches were characterized using swelling capacity, angle of repose, density measurements, Carr's index and Hausner's ratio. Metronidazole tablet formulations were made with the starches incorporated by intragranular (IG), extra-granular (EG) or intra/extragranular (IG/EG) methods. Tablet properties of crushing strength, disintegration time and dissolution tests were determined. RESULTS Native wheat starch had better hydration capacity than the modified starches, with PGS having a higher swelling capacity than the MCW. Modified starches formed better compacts than both NAS and SSG as indicated by the higher crushing strength of tablets containing modified starches. Intragranular incorporation gave a higher crushing strength than both EG and IG/EG methods. The ranking for disintegration time of tablets was IG/EG > IG > EG among the incorporation methods and SSG > PGS > MCW > NAS among the starches (EG > IG/EG). The difference between IG/EG and EG was significant (p < 0.05) but not significant between IG and other incorporation methods (MCW > SSG > PGS). Native and modified wheat starches exhibited better disintegrant properties than sodium starch glycolate in metronidazole tablet formulations. CONCLUSIONS The mode of disintegrant incorporation and modification of wheat starch had different effects on tablet properties of metronidazole formulations. The modification technique and method of disintegrant incorporation should be determined based on desired tablet properties.