according to need (physicians use PRN in writing prescriptions); add water as needed
[ Syn: as needed , as needed , as required , as required , pro re nata , pro re nata , prn , prn , as needed , as needed , as required , as required , pro re nata , pro re nata , prn , prn , as needed , as needed , as required , as required , pro re nata , pro re nata , prn , prn , as needed , as needed , as required , as required , pro re nata , pro re nata , prn , prn ]