Is there some confusion here between glass ampules and glass vials?
The only time I ever used a filter for vials was on certain drugs that can crystallize in solution and the rare cases of coring the stopper an irreplaceable drug. (working in pharmacy)
You need filters for amps because when you break then micro fine pieces fly everywhere.
As part of my training to compound cardio drugs and blocks we had a demo about glass particles. They used a certain type of lens to record us breaking them and then played it back and I was shocked to see what had looked like a clean break released a fine cloud of glass in addition to the pieces you see. We then had to pull up the fluid and look at it under a microscope. There was a huge amount of suspended glass in the solution.
On a related note, if you use a regular needle to draw from a vial, does anybody switch to a fresh, sharp needle before giving an injection? I understand the rationale that piercing the stopper dulls the needle, and a dull needle makes for a more painful injection. My instructor last semester did not change the needle. Not sure whether this is a practice I should implement this semester, or if I will be laughed off the floor?