Especially the vetergesic ones, as I have known vets and nurses to open them with their bare hands (ouch!) and the vial shatters in their hand
If you dont have one of those special vial openers, ALWAYS used a piece of tissue, or similar to protect your hands, should the vial shatter. Better safe than sorry!
the bottom of your tunic is good for this... we've had some really tough little vails of vetergesic to try and open recently... little buggers!