Which abbreviation indicates the administration of medication rectally?

The abbreviation that indicates the administration of medication rectally is "pr." This stands for "per rectum," which directly refers to the route of administration through the rectum. This method is often used for patients who may not be able to take medications orally due to various medical conditions, providing an effective alternative for medication delivery.

The other abbreviations refer to different administration routes. "pv" means "per vaginam," indicating vaginal administration. "sl" stands for "sub lingual," which refers to medications that are placed under the tongue for absorption. "ac" means "ante cibum," indicating that a medication should be taken before meals. Each of these terms specifies a unique method of administration, making "pr" distinctly associated with the rectal route.