Help with finding resources on Medication Administrationprocess

Hi,

I am a student nurse doing my last year clinicals in an ER unit. For a project at school, I want to discuss potential safety issues associated with nursing practice or care. During my days there, I notice that for pain medications PRN, some nurses will administer the amount ordered, THEN hold the med in their pockets in case the patient requests more. They have told me it is a waste to throw away the rest when the patient will most likely ask for more in one hour. I can see why nurses want to hold the medication and not waste materials, but it also poses health risks to carry around meds in pockets. (They label the needle with the vial with the patient's name tag). I found out that the hospital policy says they CAN hold the medication for a certain amount of time before wasting it. They aren't suppose to be carrying it around in their pockets, but they "can" hold it for awhile... I'm confused about where they "should" put the med in the meantime between the first administration and the second. I am wondering if there is anything in literature being written about this? And does other hospitals have policies like this?