Although some tablets consist of nothing more than the drug and an inactive filler substance compacted together, many are far more complex. Manufacturers frequently also include ingredients to hold the tablet together (binders), ingredients to aid disintegration when the tablet reaches the stomach (disintegrants), colourings to make the tablet identifiable and in very small amounts materials to help the powders move around the tablet machine during manufacture e.g. lubricants, glidants and anti-adherents. The figure below provides a diagrammatic representation of a tablet.
Manufactures spend a lot of time deciding on the level of compaction a tablet requires and in selecting inactive ingredients which don't affect the active drug and the way it is absorbed. Because active and inactive ingredients in one tablet may be incompatible with active and inactive ingredients in another it is never appropriate to crush more than one different tablet at a time.