What does the abbreviation "ad" signify in medical instructions?

The abbreviation "ad" in medical instructions is commonly understood to signify "right ear." This is derived from the Latin term "auris dextra," where "auris" means ear and "dextra" means right. In pharmacy and medical contexts, precise instructions regarding medication administration are crucial, especially when dealing with applications to the ears.

Using "ad" ensures clarity for healthcare professionals when prescribing treatments like ear drops or medications intended specifically for the right ear. This level of precision helps prevent medication errors that could arise from misunderstandings, especially if the instructions are confused with similar abbreviations.

In contrast, other options represent different terms: "both ears" would typically be denoted as "au" (auris utraque), while "left ear" is abbreviated as "as" (auris sinistra). "Buccal administration" refers to medications placed inside the cheek to dissolve, which does not relate directly to ear administration at all. Thus, understanding the specific abbreviation "ad" as meaning "right ear" is key to proper medication administration within the right context.