Abstract: This study investigates the incorporation of microcrystalline starch (MCS) as a filler/binder/disintegrant in metronidazole tablet formulation by direct compression. MCS was derived from cassava starch by partial enzymatic hydrolysis using α-amylase enzyme. Cassava starch obtained from the freshly harvested tubers of Manihot esculenta Crantz was subjected to enzymatic hydrolysis in a thermostatic water bath set to a temperature of 56ºC. The reaction was allowed to proceed for 5h at a pH of 6. Hydrolysis was terminated after 5h by lowering the pH to 3 with 0.1N HCl. It was then brought to a neutral pH 7 by the addition of 0.1N NaOH and the resulting MCS separated from the reaction mixture by centrifugation at 2800 rpm for 10 min. The MCS obtained was re-dispersed in ethanol to dehydrate it and spread out on a tray to dry at room temperature. Powder and compact characterisation of MCS was done in comparison to microcrystalline cellulose (MCC). Powder properties revealed more differences than similarities between both materials. Both materials had an angle of repose greater than 40º. Hausner’s ratio and Carr’s index were lower for MCS compared to MCC. Compaction behaviour analysed by Heckel and Kawakita equations reveals that both materials consolidate principally by plastic deformation. Tableting properties revealed that MCS has a better drug-release profile in terms of disintegration and dissolution parameters compared to MCC. This study confirms the suitability of MCS as a filler/binder/disintegrant for poorly compressible drugs.
Keywords: Microcrystalline cellulose, powder properties, compaction properties, enzymatic hydrolysis, Heckel equation and Kawakita equation.