The most widely used medicine for diarrhea is loperamide (sold as Imodium), an over-the-counter drug that slows intestinal movement so your body has more time to absorb water. For most adults with uncomplicated diarrhea, it works within an hour and is available without a prescription. But loperamide isn’t always the right choice, and the best treatment depends on what’s causing the diarrhea, how severe it is, and who’s taking it.
Loperamide: The Most Common OTC Option
Loperamide works by slowing the contractions of your intestines, which gives your gut more time to pull water and nutrients from food before it passes through. The standard adult dose is two tablets (4 mg) after the first loose stool, then one tablet (2 mg) after each subsequent loose stool. The maximum is four tablets in 24 hours for the over-the-counter version, or eight capsules per day if a doctor is managing your dosing for chronic diarrhea.
It’s effective for garden-variety diarrhea from dietary triggers, stress, or mild stomach bugs. However, you should not take loperamide if you have blood in your stool or a high fever, which can signal a more serious infection like dysentery. In those cases, slowing your gut down can actually trap the infectious organism inside rather than letting your body flush it out.
Bismuth Subsalicylate (Pepto-Bismol)
Bismuth subsalicylate is the other major over-the-counter option. It works differently from loperamide: rather than slowing your intestines, it reduces inflammation in the gut lining and decreases the amount of fluid your intestines secrete. This makes it a gentler option that also helps with nausea, heartburn, and stomach upset, which is why it’s a staple for general stomach complaints. It’s less potent than loperamide for stopping diarrhea quickly, but it treats a broader range of symptoms. The liquid and chewable tablets are dosed every 30 minutes to an hour as needed, typically up to eight doses in 24 hours.
One thing to know: bismuth subsalicylate contains a compound related to aspirin. If you’re allergic to aspirin, taking blood thinners, or giving it to a child or teenager (due to the risk of Reye’s syndrome), it’s not appropriate.
Prescription Medicines for Severe Diarrhea
When over-the-counter options aren’t enough, doctors can prescribe stronger medications. The most common is a combination of diphenoxylate and atropine (sold as Lomotil), which works similarly to loperamide but at prescription strength. It’s used alongside fluid and electrolyte replacement for severe diarrhea that hasn’t responded to OTC treatment.
This combination is not safe for children under 6 because of the risk of serious breathing problems. It’s also not used when diarrhea is caused by antibiotics or certain infections, since slowing the gut in those situations can make things worse. People with liver disease, kidney disease, or inflammatory bowel conditions like ulcerative colitis need to use it cautiously.
Antibiotics for Bacterial Diarrhea
If your diarrhea is caused by a bacterial infection, particularly traveler’s diarrhea picked up abroad, antibiotics are the treatment. The CDC lists several options depending on the destination and suspected bacteria. Azithromycin is the preferred choice for severe cases involving fever or bloody stool, and it can be taken as a single 1,000 mg dose (though splitting it into two doses the same day reduces nausea). For milder traveler’s diarrhea caused by common gut bacteria like E. coli, rifaximin is an option that stays in the intestines rather than being absorbed into the bloodstream.
Fluoroquinolone antibiotics like ciprofloxacin were traditionally the go-to, but rising resistance (especially in South and Southeast Asia) and FDA warnings about side effects including tendon damage and nerve problems have made them a less favored first choice. In Southeast Asia specifically, azithromycin is recommended as the first-line treatment because of widespread fluoroquinolone resistance.
Doctors sometimes combine an antibiotic with loperamide for faster relief. The antibiotic kills the bacteria while loperamide controls symptoms in the meantime.
Rehydration: The Treatment That Matters Most
No matter what medicine you take, replacing lost fluids and electrolytes is the single most important part of treating diarrhea. Dehydration, not the diarrhea itself, is what makes the condition dangerous. The World Health Organization’s oral rehydration solution contains a precise balance of sodium, potassium, and glucose designed to maximize water absorption. Pre-mixed ORS packets are available at most pharmacies, or you can buy pediatric electrolyte drinks like Pedialyte.
Signs that dehydration has become serious include extreme fatigue, dizziness when standing, very dark urine, dry mouth with no tears, and in severe cases, confusion or unresponsiveness. Severe dehydration requires IV fluids in a medical setting because the gut can’t absorb oral fluids fast enough to catch up. For most adults, though, steady sipping of an electrolyte solution throughout the day is sufficient.
Children Need a Different Approach
Anti-diarrheal medications like loperamide are not recommended for infants and children. The CDC’s pediatric guidelines are clear on this point. In young children, these drugs can cause dangerous side effects including severe abdominal distention, drowsiness, and slowed breathing. Cases of loperamide use in young children have been linked to deaths in clinical reports.
For children, the treatment is oral rehydration, continued feeding, and time. Pediatric electrolyte solutions are formulated with the right balance of salts and sugar for small bodies. If a child can’t keep fluids down, is producing no tears when crying, or has gone six or more hours without a wet diaper, that warrants urgent medical attention.
What About Probiotics?
Probiotics are frequently marketed for diarrhea relief, and some medical groups have recommended specific strains like Saccharomyces boulardii and Lactobacillus rhamnosus GG. However, the evidence is weaker than many people assume. A large Cochrane review found that the data does not support using probiotics for treating acute infectious diarrhea. The American Gastroenterological Association reached a similar conclusion, recommending against probiotics for acute infectious diarrhea in children in the US and Canada. While some earlier, smaller trials showed modest benefits, the larger and more rigorous studies have not confirmed them. Probiotics are unlikely to cause harm, but they shouldn’t be relied on as a primary treatment.
Choosing the Right Treatment
For a straightforward bout of loose stools lasting a day or two, loperamide plus plenty of fluids is the standard approach for adults. Bismuth subsalicylate is a reasonable alternative if you also have nausea or cramping. If diarrhea lasts more than two days, contains blood, or comes with a fever over 102°F (39°C), those are signs of something that needs medical evaluation rather than OTC treatment. Traveler’s diarrhea that doesn’t improve within 24 hours of starting self-treatment also warrants seeing a doctor, since targeted antibiotics may be necessary.