Before start of every shift, we do an equipment check. This includes checking to see if there are enough gauze pads, o2 is sufficient, enough fuel in tank, and medications. I not only check to see if they are there, but expiration. Inventory is done as a whole by someone else, medications and tracking of which ambulance they are on, is done VIA computer and can be logged in by the provider when they used something.
Expired medications such as epi, dopamine, D50, and such... are tossed in the sharps box. Other meds, such as the morphine, fentanyl, etomidate, valium, etc etc.. are taken the the ER and disposed of/wasted there with witness of an RN or MD. The MD then signs off on it and are replaced if needed. Also, narcs MUST be signed for at the start of every shift.