2.8. Soluble and Insoluble Filler MaterialsA filler is an excipient normally used in solid oral dosage forms to provide sufficient mass andvolume. Multifunctional fillers are now used in solid oral dosage forms to fulfill more than onefunction. Two major groups of pharmaceutical filler materials exist, namely aqueous soluble andaqueous insoluble fillers. Fillers for oral solid dosage forms are chosen to help reach the best possibledrug release profile from the dosage form in the environment of the human gastro-intestinal tract [1,58]