It's a stimulant.
3 seconds sound clip from the The Exorcist movie soundboard.
You can hear this line at 00:34:35 in the Blu-ray version of the movie.
Quote context
[...]
- Yeah. Why the math? What is that?
- It affects her concentration.
- Now, this is for Ritalin. -Okay.
- A stimulant? My God, she's higher than a kite now.
- Her condition isn't quite what it seems.
- And as to how or why, we really don't know.
- But... her symptoms could be overreaction to depression.
[...]