WHAT DOES THE MEDICAL TERM PRN MEAN?
PRN is a medical term that means 'take when needed'. This medical term of art is derived from Latin pro re na which means as occasion arises. The term is used medically to describe use of medication, dressings, or physical therapy modalities that we prescribe.
PRN basically means "leave it up to the patient to decide how often to use this prescribed intervention". I use prn everyday on multiple prescriptions for medications that I intend to be used intermittently e.g. ativan (a sedative) for flight anxiety, not for everyday use. The opposite of PRN is scheduled. These would be like hypertensive or diabetic medications which must be taken everyday at a prescribed time. If 'prn' is not explicity written onto a prescription then scheduled is always implied and employed.