DXM or dextromethorphan is the chemical in Robitussin. When taken in excess it will produce a psychedelic effect. To get high, take less than 20mg/kg (or 2000mg) if you exceed this dosage it most likely will be fatal. There are four kinds of experiences: the first is a mild stimulant effect, like a buzz, the second is more intoxicating, like being drunk and stoned at the same time, the third is dissociative, like a lower dose of ketamine, and the fourth is fully dissociative, like a higher dose of ketamine. DXM is comparative to PCP. Some things you may want to consider are the effects: nausea, diarrhea, vomiting, and allergic reaction, hot flashes, dizziness, and bad trips, psychotic breaks, psychological addiction and depression as well as irreversible brain damage.