Diphenoxylate is an opioid agonist used for the treatment of diarrhea that acts by slowing down intestinal contractions. It is a congener to the narcotic Meperidine of which the common brand name is Demerol. This being the case, this medication is potentially habit-forming, particularly in high doses or when long time usage is involved. Because of this, diphenoxylate is manufactured and marketed as a combination drug with atropine (Lomotil®).

This pharmaceutical strategy is designed to discourage abuse, because the anticholinergic effect of atropine will produce severe weakness and nausea if standard dosage is exceeded.

This medication is classifed as a Schedule V under the Controlled Substances Act by the Food and Drug Administration (FDA) and the DEA in the United States when used in preparations. When diphenoxylate is used alone, it is classified as a Schedule II.