<unk>  is a Latin phrase meaning "in the circumstances" or "as the circumstance arises" (literally "for the thing born"). In medical terminology, it is often abbreviated<unk>  or P.R.N. and refers to the administration of prescribed medication as the situation calls for it.
Pro re nata
De materia medica
Morire di classe
Vishnevsky liniment
Selmedica
Cervarix
Arborloo
Seasilver