The active ingredient in cough medicine, DMX or Dextromethorphan, is actually a psychoactive drug that, at high doses, causes dissociation, visual distortions, and loss of motor coordination. Though I don’t personally recommend it, some people chug cough syrup recreationally and call it “robo-tripping.”
This doesn’t seem to make sense: how can one chemical affect your sore throat and your brain? As it turns out, the purpose of the DMX in cough suppressants is to turn off the part of the brain that causes the coughing reaction to avoid irritating the throat more, but at higher doses ends up turning off other parts of the brain, too. Your “reptile brain” gets confused, causing disconnects in your experience of the mind/body relationship.
Sources:
Jace Harr 