adjuvant
agent that modifies or enhances the effect of other agents such as drugs or vaccines while having few if any direct effects when given by itself
en-GB/əˈd͡ʒuːvənt/
en-US/ˈæd͡ʒəvənt/
agent that modifies or enhances the effect of other agents such as drugs or vaccines while having few if any direct effects when given by itself