Which abbreviation indicates administration by mouth?

• A. p.o
• B. a.c.
• C. p.c.
• D. ad lib

Answer: (A)

Oral administration is indicated by p.o. (per os), meaning the medication is meant to be swallowed. This is the abbreviation that designates administration by mouth. The other terms refer to timing or conditions: a.c. means before meals, p.c. means after meals, and ad lib means at one’s discretion. So p.o. uniquely denotes the oral route.