Rectal Medication Administration

Rectal administration can provide a local effect in the rectum or a systemic effect after absorption through the rectal mucosa. It is useful when swallowing is unsafe or impossible, the oral route is unavailable or contraindicated, or the prescribed medication is intended to act locally. Absorption through the rectum is less predictable than absorption through a consistently functioning oral route. Some blood from the lower rectum drains directly into systemic circulation and may partly avoid hepatic first-pass metabolism, whereas blood from the upper rectum enters the portal circulation first. The insertion site, stool or diarrhea, retention time, formulation, and mucosal condition can all change how much medication reaches the circulation. A rectal dose therefore cannot automatically be treated as equivalent to an oral, subcutaneous, or intravenous dose. The formulation determines the procedure. Suppositories are solid preparations that soften, melt, or dissolve. Enemas and foams may be intended for local treatment, bowel evacuation, or systemic absorption. Check the product monograph and agency procedure rather than applying one technique or one expected onset to every rectal medication.