From the Latin: pro re nata
which translates into meaning in the circumstances or as the circumstance arises
In medicine, as means take as needed.
You will find many narcotic prescriptions written this way. 1 to 2 tablets as needed
Many other prescribed medications are are a specific schedule (ie 1 in the am, 1 before going to bed, etc)
But with PRN, the decision of when to administer the drug is left to the nurse, caregiver or the patient's prerogative. Such administration of medication is not meant to imply, and should never allow for, exceeding a given daily dosage.
Ron DiLauro Spine-Health System Administrator I am not a medical professional. I comment on personal experiences