Taking an anti-diarrheal medication may reduce or completely eliminate loose stools after the first dose. Look for over-the-counter products like Imodium or Pepto-Bismol, which have the ingredients loperamide and bismuth subsalicylate, respectively. The active ingredient, loperamide, in Imodium works swiftly because it slows the movement of fluid through the intestines. This can quickly restore normal bowel function. Pepto-Bismol, on the other hand, helps kill diarrhea-causing bacteria in your intestines.