When do u use a filter needle? pharmacy question?

You use a filter needle when the liquid medication you are drawing into a syringe is taken from an ampule that you have had to crack open. The ampule is a small glass container and the 'top' of it is broken off in a way that can cause very small glass shards to go inside it. You wouldn't want to use anything but a filter needle to draw that up, because then you might be injecting those glass pieces into your body.