Editing Excipient (section)

==Relative versus absolute inactivity==
Though excipients were at one time assumed to be "inactive" ingredients, it is now understood that they can sometimes be "a key determinant of dosage form performance";<ref name="bhatta2006" /> in other words, their effects on [[pharmacodynamics]] and [[pharmacokinetics]], although usually negligible, cannot be ''known'' to be negligible without [[empirical evidence|empirical confirmation]] and sometimes are important. For that reason, in [[basic research]] and [[clinical trial]]s they are sometimes included in the [[scientific control|control substances]] in order to minimize [[confounding]], reflecting that otherwise, the absence of the active ingredient would not be the only variable involved, because absence of excipient cannot always be assumed not to be a variable.<ref name="science">{{cite journal |title=The activities of drug inactive ingredients on biological targets |author=JOSHUA POTTEL |journal=[[Science (journal)|Science]] |date=July 24, 2020 |volume=369 |issue=6502 |pages=403–413 |doi=10.1126/science.aaz9906 |pmid=32703874 |pmc=7960226 |bibcode=2020Sci...369..403P }}</ref> Such studies are called excipient-controlled or [[#Vehicles|vehicle]]-controlled studies.