Which of the following medications is used to treat diarrhea?

Lomotil is the correct choice for treating diarrhea because it is a combination of diphenoxylate, an opioid that slows down gut motility, and atropine, which helps to reduce the likelihood of misuse and enhances the antidiarrheal effect. By slowing down the movement in the intestines, Lomotil allows for more water to be absorbed from the fecal matter, helping to firm up loose stools and reduce the frequency of bowel movements.

Medrol is a corticosteroid primarily used to reduce inflammation and suppress the immune response, and it does not have a role in managing diarrhea. Cleocin, or clindamycin, is an antibiotic used to treat bacterial infections, particularly those caused by anaerobic bacteria but is not utilized for diarrhea treatment. Valtrex, or valacyclovir, is an antiviral medication employed mainly to treat infections caused by certain types of viruses, such as herpes simplex, not for managing gastrointestinal conditions like diarrhea. Thus, Lomotil specifically addresses the symptoms associated with diarrhea effectively.