The question is a little vague but, as far as I am aware - not in a useful sense. Four things that might be considered as such are:
Nicotine - not medically useful for anything, in fact harmful.
Crack cocaine - not medically useful for anything, in fact harmful.
Oxygen - which may increase oxygenation but increases oxidative stress, acting as a poison as it does so.
Smelling salts - which are pretty limited in what they can do.
