Erowid DXM FAQ
There are four different kinds of experiences, based on the dosage; these are called plateaus. The first plateau is a mild stimulant effect with a little bit of a buzz, and has been compared to MDA. The second plateau is more intoxicating and has been compared to being drunk and stoned at the same time. The third plateau is dissociative, like a lower dose of ketamine. The fourth plateau is fully dissociative like a higher dose of ketamine.
You should not attempt higher plateau doses unless you have someone with you who can take care of you in case you get sick or freak out. It happens on DXM. Many things can happen unexpectedly on upper plateaus, such as spontaneous memory recall, complex delusions, hallucinations, out-of-body experiences, near-death experiences, and perceived contact with spiritual or alien entities. You need to be pretty stable and grounded before you can handle these things.