The opposite of amphetamines is stimulants increase breathing and heart rate while depressants slow these functions.
Stimulants are the opposite of depressants, also colloquially referred to as downers as they reduce the level of arousal when taken.
Whereas Stimulants" increase mental and physical function.
Hence the opposite drug class of depressants is stimulants, not antidepressants.
Thus, to learn more about depressants click here:
https://brainly.com/question/17642418