Final answer:
The correct abbreviation for "as needed" is PRN.
Step-by-step explanation:
The correct abbreviation for "as needed" in the context of medication orders is PRN.
PRN stands for "Pro re nata," which is a Latin phrase meaning "as the situation demands" or "as needed." It is commonly used in healthcare to indicate that a medication should be administered when the patient requires relief from symptoms, rather than on a specific schedule.
For example, if a patient has a prescription for a painkiller to be taken PRN, they would only take it when they experience pain that needs to be managed.