Per os

Per os (P.O.) is an adverbial phrase meaning literally from Latin "by mouth" or "by way of mouth." The expression is used in medicine to describe a treatment that is taken orally. The abbreviated P.O. is often used on medical prescriptions.

P.O. is also occasionally rendered per orem, which is sometimes corrupted to per oram, both of which also mean "by mouth."

Pronunciation

 * British: pər'əoυs
 * U.S.: pər'oυs