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

Lactose granulations (125-250 mu m) were prepared from two different a lpha-lactose monohydrate powders and one roller dried beta-lactose pow der respectively, by wet granulation with only water as a binder. As a n 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 dependen t on the type of lactose, the surface area of the starting powder and the granule bulk density. For lubricated lactose granulations, the lub ricant sensitivity, expressed as Lubricant Sensitivity Ratio (LSR), in creased with an increase of bulk density. The beta-lactose content of roller-dried beta-lactose is hardly affected by the granulation proces s, which explains the good compactibility of the granule fractions pre pared from this type of lactose. On the other hand, anhydrous alpha-la ctose present in the roller-dried beta-lactose starting material is co nverted into alpha-lactose monohydrate during the granulation process, which improves tablet disintegration. The compaction properties of co mmercially available lactose granulations have been compared with thos e of the experimental granulations and with a free flowing sieved alph a-lactose monohydrate. As an effect of the higher powder surface area and the relatively low bulk density, Tablettose(R) has a better compac tibility than alpha-lactose monohydrate 100 Mesh. The excellent compac tibility of another commercially available lactose granulation, Pharma tose(R) DCL 15, was attributed to the presence of more beta-lactose, p roviding strong intergranular cohesion.