Which of these abbreviations indicates administration in both ears?

The abbreviation that indicates administration in both ears is "AU," which stands for "auris utraque" in Latin. This term translates to "each ear" or "both ears," making it the appropriate abbreviation to use when medication is being prescribed or administered to both ears simultaneously.

In a clinical setting, it is important to clearly communicate whether a treatment is intended for one ear or both to ensure proper medication delivery and avoid potential complications. The other options represent different specific medical abbreviations: "OD" refers to the right eye, "OS" refers to the left eye, and "AS" refers to the left ear, thus they do not indicate administration in both ears. The clarity and specificity of these abbreviations are crucial in pharmacology to avoid any misunderstanding in prescriptions.