In several scenes, the super evil DEA guy Stan is seen taking pills, then cracking his neck. What is he doing that for?
I have seen two scripts for this movie. In one, it was Flexoril (muscle relaxers), which makes sense because this is why he is poping his neck.
The other version was Downers, and the crunching sound was actually the pill being crused in his mouth. I don’t like this version though, Leon was too cool. 
I saw the movie a little while ago, and I got the sense he was taking speed or something similar. I don’t remember what gave me this impression, but he does seem high shortly after he takes them and says some pretty bizarre stuff. Plus, it’d be ironic that the DEA officer (who’s storing drugs) is himself using them… But then again, maybe Stan’s just weird. I’ll defer to robgruver since he’s seen the scripts.