How to stop diarrhea: Anti-diarrheal medications - such as loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol) and kaolin pectin suspension (Kaopectate) - can reduce the severity of symptoms but won’t speed recovery. They also can worsen or prolong diarrhea caused by parasites or bacteria. If a parasite or bacterial infection has caused diarrhea, a course of antibiotics may be prescribed. Occasionally treatment with antibiotics for another condition can result in disruption of normal flora in the intestines and overgrowth of pathogenic strains of bacteria, resulting in very severe diarrhea. This type of diarrhea requires immediate discontinuation of the course of antibiotics and specialized treatment.