TABLETING PROPERTIES OF EXPERIMENTAL AND COMMERCIALLY AVAILABLE LACTOSE GRANULATIONS FOR DIRECT COMPRESSION

Lactose granulations (125-250 mu m) were prepared from two different alpha-lactose monohydrate powders and one roller dried beta-lactose powder respectively, by wet granulation with only water as a binder. As an effect of the granulation process, the flow properties improved, but the compactibility decreased. Moreover, the lubricant sensitivity of the granule fractions was higher than found for the starting materials. The compactibility of the granule fractions was found to be dependent on the type of lactose, the surface area of the starting powder and the granule bulk density. For lubricated lactose granulations, the lubricant sensitivity, expressed as Lubricant Sensitivity Ratio (LSR), increased with an increase of bulk density. The beta-lactose content of roller-dried beta-lactose is hardly affected by the granulation process, which explains the good compactibility of the granule fractions prepared from this type of lactose. On the other hand, anhydrous alpha-lactose present in the roller-dried beta-lactose starting material is converted into alpha-lactose monohydrate during the granulation process, which improves tablet disintegration. The compaction properties of commercially available lactose granulations have been compared with those of the experimental granulations and with a free flowing sieved alpha-lactose monohydrate. As an effect of the higher powder surface area and the relatively low bulk density, Tablettose(R) has a better compactibility than alpha-lactose monohydrate 100 Mesh. The excellent compactibility of another commercially available lactose granulation, Pharmatose(R) DCL 15, was attributed to the presence of more beta-lactose, providing strong intergranular cohesion.