**4.2 MCC as wet granulation filler**

MCC is one of the types of filler which is water insoluble having swelling tendencies and excellent water imbibing or wicking action. Other filler examples with the same property are calcium pectinate and sodium alginate. This property makes MCC as also an excipient of choice for wet granulation. Both Avicel PH 101 and Avicel PH 102 can be used advantageously as fillers in wet granulation in a concentration of 5.15%. When used as filler in wet granulation method, the wicking action of MCC promotes rapid wetting of the powder mix. Another advantage offfered by using MCC as wet granulation filler is the ability to retain water, which makes the wet mass less sensitive to overwetting due to an excess of granulating fluid. The milling of the wet mass will be much easier due to less clogging of the screen; hence it will produce a more uniform granules. Drying process also will be more homogeneous, and the case of hardening can be reduced. Case hardening is a phenomenon

which is observed in incompletely dried granules. This case happened when the granules are dried at a high temperature, from which the inside part of the granules remains wet, while the surface seems dried. The granules are often hard and resist disintegration. When coming to compaction process, the compression forces will break the granules and deform plastically to form soft tablets due to the moisture coming out of the incompletely dried granules. The use of Avicel PH 101 or Avicel PH 302 as filler in wet granulation promotes rapid wetting as a result of the wicking action of MCC. They reduce sensitivity of the wet mass to overwetting and increase the drying process speed. Since there is fewer excess of granulating fluid, screen blockages and case hardenings can be reduced. Homogeneous and uniform granule when MCC is used as wet granulation filler will reduce dye migration. When MCC is employed, faster disintegration from granules and tablets will be obtained.
