Two over-the-counter medications are effective for treating diarrhea in adults: loperamide (sold as Imodium) and bismuth subsalicylate (sold as Pepto-Bismol and Kaopectate). They work differently, suit different situations, and have different safety considerations worth knowing before you grab one off the shelf.
Loperamide: The Strongest OTC Option
Loperamide slows the muscle contractions in your intestines, giving your body more time to absorb water from stool. This makes it the most effective OTC choice for stopping frequent, watery bowel movements quickly. The American College of Gastroenterology recommends it as a first-line option, and it can also be used alongside antibiotics if your doctor prescribes them for traveler’s diarrhea.
For OTC use, the standard approach is to take 4 mg (two caplets) after your first loose stool, then 2 mg (one caplet) after each subsequent loose stool. The maximum for OTC use is 8 mg in 24 hours, which means four caplets total. Prescription doses can go up to 16 mg per day, but you shouldn’t exceed the OTC limit on your own. The ACG also advises not using loperamide for more than 48 hours without medical guidance.
One important safety note: loperamide is safe at recommended doses, but taking significantly more than directed can cause dangerous heart rhythm problems, including cardiac arrest. The FDA issued specific warnings about this after reports of misuse. Stick to the label directions, and if you notice a rapid or irregular heartbeat, fainting, or unresponsiveness in someone who has taken loperamide, call 911 immediately.
Avoid loperamide if you have bloody stools or a high fever. These signs suggest an infection where slowing your gut down could actually make things worse by keeping the pathogen inside longer.
Bismuth Subsalicylate: Gentler and Broader
Bismuth subsalicylate takes a different approach. It reduces the amount of fluid your intestines secrete while also fighting bacteria and viruses directly. Lab research from the CDC confirmed that bismuth compounds reduced bacterial growth dramatically across multiple common diarrhea-causing pathogens, and also lowered the infectivity of norovirus. This makes it a reasonable pick when you suspect a mild stomach bug or food poisoning, or when you’re dealing with general stomach upset alongside diarrhea (nausea, heartburn, indigestion).
The recommended dose is two tablets (525 mg total) chewed every 30 to 60 minutes as needed, up to eight doses in 24 hours. It won’t stop diarrhea as abruptly as loperamide, but it works on multiple fronts and is generally gentler. Don’t be alarmed if your tongue or stool turns black temporarily. That’s a harmless reaction between bismuth and trace sulfur in your saliva and digestive tract.
Because bismuth subsalicylate contains a compound related to aspirin, it carries real restrictions. Do not give it to children or teenagers who have or are recovering from the flu, chickenpox, or other viral infections, as it raises the risk of Reye’s syndrome, a rare but serious condition affecting the brain and liver. If you take blood thinners or are allergic to aspirin, skip this one entirely.
What About Probiotics?
Probiotic supplements are widely marketed for digestive health, and there is some evidence behind specific strains. A meta-analysis of six randomized trials found that Saccharomyces boulardii, a beneficial yeast sold under brand names like Florastor, shortened diarrhea duration by about 1.6 days compared to no treatment in children with acute diarrhea.
That said, the American College of Gastroenterology does not recommend probiotics for treating acute diarrhea in adults, except when the diarrhea is caused by antibiotic use. If you’re dealing with diarrhea that started after a course of antibiotics, a probiotic is worth trying. For a standard stomach bug, loperamide or bismuth subsalicylate will do more.
Products That Don’t Actually Help
Older remedies like kaolin, pectin, activated charcoal, and attapulgite (once found in the original Kaopectate formula) may make your stool look more formed, but they don’t reduce the number of bowel movements or shorten how long diarrhea lasts. The ACG specifically recommends against them. If you see these ingredients on a product label, save your money.
Staying Hydrated Matters More Than Food Choices
The biggest risk from acute diarrhea isn’t the diarrhea itself. It’s dehydration. You lose water and electrolytes with every loose stool, so your priority is replacing both. Water alone helps, but oral rehydration solutions (like Pedialyte or similar electrolyte drinks) are better because they replace sodium and potassium at the same time. Sports drinks work in a pinch, though they contain more sugar than ideal.
As for eating, the old BRAT diet (bananas, rice, applesauce, toast) is fine for a day or two but unnecessarily restrictive. Harvard Health notes there are no studies showing BRAT is better than simply eating bland, easy-to-digest foods. Brothy soups, oatmeal, boiled potatoes, crackers, and plain cooked chicken are all good choices. Once your stomach settles, add back nutrient-dense foods like cooked squash, sweet potatoes, avocado, fish, and eggs. You need protein and calories to recover, not just starch.
Signs That OTC Treatment Isn’t Enough
Most episodes of acute diarrhea resolve within a few days. But certain symptoms signal something more serious. For adults, seek medical attention if diarrhea persists beyond two days without any improvement, if you develop a fever above 102°F, if you see blood or black color in your stool, or if you have severe abdominal or rectal pain. For children, the timeline is shorter: no improvement within 24 hours, fever above 102°F, or bloody stools all warrant a call to the pediatrician.