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Microcrystalline Cellulose
I.P. Microcrystalline Cellulose is a naturally occurring substance that is proven stable, safe and physiologically inert. Microcrystalline Cellulose revolutionized tableting because of its unique compressibility and carrying capacity. It exhibits excellent properties as an excipient for solid dosage forms. It compacts well under minimum compression pressures, has high binding capability and creates tablets that are extremely hard, stable, yet disintegrate rapidly. Other advantages include low friability, inherent lubricity, and the highest dilution potential of all binders. These properties make Microcrystalline Cellulose particularly valuable as a filler and binder for formulations prepared by direct compression, although it is also used in wet or dry granulation. WHAT IS MICROCRYSTALLINE CELLULOSE? As the name implies, Microcrystalline Cellulose is cellulose derived from high quality wood pulp. While cellulose is the most abundant organic material, Microcrystalline Cellulose can only be derived from a special grade of alpha cellulose. In many ways, Cellulose makes the ideal excipient. A naturally occurring polymer, it is comprised of glucose units connected by a 1-4 beta glycosidic bond. These linear cellulose chains are bundled together as microfibril spiralled together in the walls of a plant cell. Each microfibril exhibits a high degree of three-dimensional internal bonding resulting in a crystalline structure that is insoluble in water and resistant to reagents. There are, however, relatively weak segments of the microfibril with weaker internal bonding. These are called amorphous regions but are more accurately called dislocations since microfibril containing single-phase structure. The crystalline region is isolated to produce Microcrystalline Cellulose. Processing of the cellulose microfibrils begins with shredding the sheets of high purity alpha grade pulp. The shredded pulp is immersed in a hot bath of mineral acid that dissolves the amorphous regions of the microfibrils while leaving the microcrystalline segments intact. The object is to break down the long polymer chains. Hydrolysis is carried to the point where a levelling off degree of polymerization (LODP) is achieved. Consistency in LODP is checked routinely by quality control personnel. Following hydrolysis, chemicals and impurities are removed through a water-washing step. This is followed by spray drying. The slurry is sprayed through hot air jets to evaporate the water. This process produces particles of the desired size and moisture content. While the process of producing Microcrystalline Cellulose appears to be relatively straightforward, the product quality is directly tied to various parameters of the process in terms of time, temperature, pressure, purity of materials and the manufacturing environment. Microcrystalline Cellulose is purified partially de-polymerized ALPHA CELLULOSE. It is white, odourless, tasteless and is free from organic and inorganic contaminations. It is insoluble in water, dilute acids and in most organic solvents. It is practically insoluble in sodium hydroxide solution. Microcrystalline Cellulose is universally used in the pharmaceutical and nutraceutical industries and is necessary for quality products. Rapid drying produces aggregates of micro-crystals with many dislocations and slip planes that can fracture and realign during tableting. This deformation is primarily plastic, so bonds formed under pressure remain formed after pressure is released, making for a strong, dense tablet with no capping. Microcrystalline Cellulose also is highly absorptive due to the capillary action of its surface porosity, making it possible to act as a carrier for liquids and yet retain free flowing and compression properties. Its porosity promotes easy wetting and rapid drying of wet granulation and exhibits good volumetric flow characteristic with low lubricant demand. |