pro re nata

From the Latin phrase pro (“for”) rē (“thing, matter”) nātā (“born, arisen”): "for what arises".

• (US) IPA^(key): /ˌpɹoʊˌreɪˈnɑ.tɑ/

pro re nata (abbreviated PRN)

1. Dealing with something that arises unexpectedly or out of due course; for special business.
2. (medicine) Used on medical charts by doctors to indicate that actions may be taken at the discretion of nursing staff depending on the patient's condition, and on prescriptions to indicate that the medicines may be taken if and when the patients feel the need)