Int. J. Pharm. Sci. Rev. Res., 22(2), Sep – Oct 2013; nᵒ 03, 13-17 ISSN 0976 – 044X International Journal of Pharmaceutical Sciences Review and Research Available online at www.globalresearchonline.net 13 * Chime S. A., Onyishi V. I., Onyechi J. O. Department of Pharmaceutical Technology and Industrial Pharmacy, University of Nigeria, Nsukka 410001, Nigeria. * Corresponding author’s E-mail: emmymarachi@yahoo.com Accepted on: 11-12-2012; Finalized on: 30-09-2013. ABSTRACT The objective of the work was to produce co-processed metronidazole granules and to formulate metronidazole tablets by direct compression. Potato starch was extracted from Ipomoea batatas, the starch obtained was pregelatinized. Co-processed metronidazole granules were formulated using 10 % of pregelatinized potato starch and 0, 2, 4 and 6 %w/w of polyvinylpyrrolidone (PVP) as binders. The flow properties of the granules were assessed using direct and indirect methods. The tablets were formulated by direct compression using potato starch as the extra granular disintegrant (3.5 %) and magnesium stearate as lubricants. The properties of the tablets were evaluated using official and non official tests. The results of the study showed that the flow properties of the granules were good and fell within acceptable limits for good tablet production. Metronidazole granules showed fast disintegration time, good hardness and also complied with BP specification for tablets weight uniformity. The friability results were significantly lower than 1 % for all the tablets batches (p < 0.05). The tablet formulations showed a fast release of the drug with maximum release (T100) at 24 min in most formulations. Therefore, metronidazole tablets could be formulated by direct compression in order to enhance the oral bioavailability of this drug. Keywords: Co-processing, metronidazole, direct compression, potato starch, pregelatinization. INTRODUCTION he disintegration of tablets in most cases is the rate limiting step to dissolution and overall bioavailability of drugs. Co-processing have been develop to address these issues enhance the tabletting processes by providing a new material (adjuvant or active ingredients) that could be formulated by direct compression. Co-processing was developed primarily to address the issues of flowability, compressibility, and disintegration potential, with filler–binder combinations being the most commonly tried. Co-processing of excipients in the pharmaceutical industry can be dated back to the late 1980s with the introduction of co- processed microcrystalline cellulose and calcium carbonate 1-2 . Co-processing is one of the most widely explored and commercially utilized methods for the preparation of directly compressible adjutants 3-4 . Co- processing is based on the novel concept of two or more excipients interacting at the subparticle level, the objective of which is to provide a synergy of functionality improvements as well as masking the undesirable properties of individual excipients 1-2 . Co-processed materials have advantage of improved compressibility, reduced fill weight variation, high dilution potential and reduced lubricant sensitivity. Pharmaceutical manufacturers have the option of using a single excipient with multiple functional properties, thereby reducing the number of excipients in inventory and improved organoleptic properties 1 . The fundamental solid-state properties of the particles such as morphology, particle size, shape, surface area, porosity, and density influence excipient functionalities such as flowability, compactability, dilution potential, disintegration potential, and lubricating potential 1 . Direct compression is the simplest and most economical method for the manufacturing of tablets because it requires less processing steps than other techniques 5 . The simplicity of the direct compression process is apparent from a comparison of the steps involved in the manufacture of tablets by wet granulation, roller compaction and direct compression techniques 6 . It has been estimated that less than 20 percent of pharmaceutical materials can be compressed directly into tablets due to lack of flow, cohesion properties and lubrication. Therefore, they must be blended with other directly compressible ingredients to manufacture satisfactory tablets. In the development of directly compressible granules by the modification of a single substance, Co-processing of two or more components was applied to produce composite particles or co‐processed excipients 5 . The composite particles or co‐processed multi‐component‐based excipients are introduced to achieve better powder characteristics and tabletting properties than a single substance or the physical mixture 6 . Directly compressible adjuvants can be prepared by various methods such as physical modification, crystallization, granulation, spray drying, co- processing and co-precipitation 3 . Direct compression technique involves simply the compression of dry blend of powders that comprises the drug and various excipients. The simplicity and cost-effectiveness of the direct compression process have positioned it as a preferred alternative to other methods of tablets production 1 . Co-processed M etronidazole Granules for Tabletting: Formulation and In Vitro Evaluation T Research Article