In the video game Metal Gear Solid the real-life drug diazepam is taken to steady your character's aim while he fires the PSG1 sniper rifle.
In the sequel to this game (aptly titled Metal Gear Solid 2) the fictional drug "Pentazemin" is used for the same purpose.
This subtle change is a tiny symptom of the large problems MGS2 has with regards to suspension of disbelief.