When medications are stored on patient care units, it may be easy to select the wrong medication or dose. Staff members may also forget to record what they select or administer. Dispensing machines often have mechanisms to help prevent these errors — for example, the machine can require that a patient identification number be entered before a medication will be dispensed. Many dispensing machines can also interface with hospital computer systems to integrate their data with information from order entry systems and medication administration records. Dispensing machines can also issue alerts and ask whether an adverse drug event has occurred whenever the machine dispenses a common reversal agent or antidote.