Alcohol 'negates' the effects of the medicine. [=alcohol prevents the medicine from working]
The fact that she lied about her work experience 'negated' the contract.
a verb that is 'negated' by “not”
(..) JACKSON: This is all the movements happening on the set... ...so you don't need to be doing much with the camera. Because it'll sort of start to negate the actual action that's happening on the set. In the cave, a little crack appears... ...and sand disappearing down this crack. (..)2012 The Hobbit: An Unexpected Journey