Excipient
An excipient is a substance formulated alongside the active ingredient of a medication , included for the purpose of long-term stabilization , bulking up solid formulations that contain potent active ingredients in small amounts ( thus often referred to as "bulking agents" , "fillers" , or "diluents" ) , or to confer a therapeutic enhancement on the active ingredient in the final dosage form , such as facilitating drug absorption , reducing viscosity , or enhancing solubility . 
<triplet> active ingredient <subj> medication <obj> part of <triplet> medication <subj> drug <obj> subclass of <triplet> drug <subj> medication <obj> different from