The two main over-the-counter medicines that stop diarrhea are loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol). Loperamide is the stronger option and works by slowing down the movement of your intestines, giving your body more time to absorb water from stool. Bismuth subsalicylate is milder and better suited for cases where diarrhea comes with nausea or an upset stomach. Which one you should reach for depends on your symptoms, your age, and whether you’re pregnant or breastfeeding.
Loperamide: The Fastest OTC Option
Loperamide is the most effective over-the-counter medicine for stopping diarrhea quickly. It works by slowing the muscles in your intestinal wall, which reduces how fast food and liquid move through your system. This gives your gut more time to absorb water, making stools firmer.
The standard approach for adults is to take two tablets (4 mg) after the first loose bowel movement, then one tablet (2 mg) after each additional loose stool. If you’re using the tablet form sold for self-treatment, the maximum is 4 tablets (8 mg) in 24 hours. Prescription-strength capsules allow up to 8 capsules (16 mg) per day, but only under a doctor’s guidance.
Loperamide is generally well tolerated at recommended doses, but it’s important to stay within the limits. At extremely high doses (50 to 300 mg, far beyond what’s recommended), loperamide has been linked to serious heart rhythm problems. The CDC has documented cases of cardiac toxicity from loperamide abuse. At normal doses this isn’t a concern, but it’s a good reason not to double up thinking more will work faster.
Bismuth Subsalicylate: For Milder Symptoms
Bismuth subsalicylate treats diarrhea, heartburn, indigestion, and nausea. It’s a good choice when your stomach feels off in multiple ways, not just loose stools. The typical adult dose is 2 tablets every 30 minutes to an hour as needed, up to 16 tablets in 24 hours. For the liquid form, it’s 2 tablespoons on the same schedule, with a cap of 16 tablespoons daily for regular strength or 8 for the concentrated version.
One important caution: bismuth subsalicylate contains a compound related to aspirin. If you’re breastfeeding, avoid it entirely. The salicylate transfers into breast milk and can reach your baby. It’s also not recommended for children or teenagers recovering from flu or chickenpox due to the risk of Reye’s syndrome, a rare but serious condition.
Prescription Medicines for Persistent Diarrhea
When over-the-counter options aren’t enough, doctors can prescribe stronger medications. The most common is diphenoxylate combined with atropine. Like loperamide, it works by decreasing bowel activity, but it’s more potent. It’s also a controlled substance because it can be habit-forming. The atropine is added intentionally to cause unpleasant side effects if someone takes more than prescribed, which serves as a built-in deterrent against misuse. Prescriptions can only be refilled a limited number of times.
For traveler’s diarrhea or diarrhea caused by bacterial infections, antibiotics may be appropriate. The CDC recommends matching the treatment to how severe the illness is. Mild traveler’s diarrhea, the kind that’s annoying but doesn’t stop you from doing what you planned, doesn’t need antibiotics at all. Moderate cases that interfere with your activities can be treated with antibiotics. Severe diarrhea that’s incapacitating, or any case involving bloody stool or fever, calls for antibiotic treatment. The specific antibiotic depends on the region you’re traveling in and whether the infection appears invasive.
Probiotics as a Supporting Treatment
Probiotics won’t stop diarrhea as fast as loperamide, but they can shorten its duration and help prevent it in certain situations. A large meta-analysis found that probiotics reduced the risk of antibiotic-associated diarrhea by 52% and acute diarrhea from various causes by 34%. The effect was even stronger in children, with a 57% reduction in acute diarrhea risk compared to 26% in adults.
Several strains have been studied, including Saccharomyces boulardii and Lactobacillus rhamnosus GG. The research didn’t find a significant difference in effectiveness between individual strains, so you don’t need to hunt for one specific product. If you’re taking antibiotics and want to reduce the chance of diarrhea as a side effect, starting a probiotic at the same time is a reasonable strategy.
Safety for Children and During Pregnancy
Over-the-counter anti-diarrheal medicines are not recommended for children under 2. They can also be harmful in older children, so it’s worth checking with a pediatrician before giving any diarrhea medication to a child. For young kids, the priority is preventing dehydration through oral rehydration solutions rather than stopping the diarrhea itself.
During pregnancy, loperamide is generally considered the safer of the two main OTC options, though you should confirm with your provider. Bismuth subsalicylate should be avoided during both pregnancy and breastfeeding because of its salicylate content. If you’re nursing and need diarrhea relief, loperamide is the better choice.
When Diarrhea Needs More Than Medicine
No matter which medicine you take, replacing lost fluids is the most critical part of managing diarrhea. Water alone isn’t ideal because you’re also losing electrolytes. Oral rehydration solutions, broth, or drinks with sodium and potassium are better options.
Some signs mean the diarrhea itself needs medical attention, not just symptom relief. For adults, those include: diarrhea lasting more than two days without improvement, a fever above 102°F, bloody or black stools, severe abdominal or rectal pain, and signs of dehydration like excessive thirst, very dark urine, dizziness, or little to no urination. For children, the timeline is shorter. Diarrhea that doesn’t improve within 24 hours, no wet diaper for three or more hours, a fever over 102°F, bloody stools, or unusual drowsiness all warrant prompt medical evaluation. Skin that doesn’t flatten when pinched and released, or a sunken appearance around the eyes or cheeks, are signs of significant dehydration in a child.