Morphine is used to cure a player of broken bones. It has a chance to spawn in all military, residential and industrial loot spawns but is most commonly found in medical tents and hospitals. Morphine can be used on yourself or another player with the mouse wheel menu.
Morphine is important to stock up on since bones can be broken by being shot in the leg, being bitten by a zombie, falling a short distance or while standing up/being prone on stairs, in doorways and beside tree roots. Morphine Auto-Injectors take one slot of your inventory or bag pack.