Two over-the-counter medicines are the go-to treatments for diarrhea in adults: loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol). They work in different ways and are suited to slightly different situations, so choosing between them depends on what’s causing your symptoms and how severe they are. Replacing lost fluids matters just as much as any pill you take.
Loperamide: The Fastest Option
Loperamide slows down the muscle contractions in your intestines, giving your body more time to absorb water from stool. It also reduces the amount of fluid your gut secretes. The result is fewer, firmer bowel movements, often within an hour or two of the first dose.
For acute diarrhea in adults, the standard approach is to take two tablets (4 mg total) after your first loose bowel movement, then one tablet (2 mg) after each subsequent loose stool. The over-the-counter maximum is 4 tablets (8 mg) in 24 hours. Prescription-strength versions allow up to 8 capsules (16 mg) per day for chronic diarrhea, but only under a doctor’s supervision.
Loperamide works well for common, non-serious causes of diarrhea: something you ate, stress, mild stomach bugs. It is not safe to use when you have bloody stools, a high fever, or a suspected infection with C. difficile (a bacterial infection that sometimes follows antibiotic use). In those cases, slowing your gut down can trap the harmful bacteria inside and make things significantly worse.
Bismuth Subsalicylate: A Gentler Alternative
Bismuth subsalicylate takes a different approach. When it reaches your stomach, it breaks into two active components. One has antimicrobial properties, preventing bacteria from attaching to the lining of your gut. The other reduces inflammation by blocking the same chemical pathway that ibuprofen targets, which calms the irritated tissue driving your diarrhea. On top of that, it stimulates your intestines to reabsorb fluid, sodium, and chloride, directly counteracting the fluid loss that makes diarrhea so dehydrating.
This combination makes bismuth subsalicylate particularly useful for traveler’s diarrhea and mild food-related illness where bacteria may be involved. It also helps with nausea and upset stomach, which loperamide does not. The tradeoff is that it’s slower-acting and generally less potent at stopping stool frequency compared to loperamide. It can temporarily darken your tongue and stool, which is harmless but can look alarming.
Because it contains a salicylate (the same family of compounds as aspirin), you should avoid it if you take blood thinners or are allergic to aspirin. It’s also not appropriate for children or teenagers recovering from flu or chickenpox due to the risk of Reye’s syndrome.
Why Fluids Matter More Than Medicine
The biggest danger from diarrhea isn’t the diarrhea itself. It’s dehydration. Every loose stool pulls water, sodium, and potassium out of your body. Mild dehydration causes fatigue, dizziness, and dry mouth. Severe dehydration can become a medical emergency, especially in young children and older adults.
Oral rehydration solutions are specifically designed to replace what diarrhea takes. The World Health Organization formula contains a precise balance of sodium, potassium, and glucose. The glucose is there because it helps your intestines absorb sodium and water far more efficiently than water alone. You can buy premade versions (Pedialyte is the most common in the US) or mix packets available at most pharmacies. Sports drinks contain too much sugar and not enough sodium to be ideal, but they’re better than plain water if nothing else is available.
For most adults with mild diarrhea, drinking broth, diluted juice, and water throughout the day is sufficient. If you’re having more than six loose stools a day or can’t keep fluids down, an oral rehydration solution becomes more important.
Prescription Medicines for Persistent Diarrhea
When over-the-counter options aren’t enough, doctors sometimes prescribe a combination of diphenoxylate and atropine. Diphenoxylate activates opioid receptors in the gut’s nervous system, which slows intestinal contractions and extends the time food spends in your digestive tract. This allows more water to be absorbed before stool reaches the end of the line. A small amount of atropine is included in the formulation specifically to discourage misuse, since diphenoxylate is technically an opioid.
This prescription is used for conditions like diarrhea-predominant irritable bowel syndrome, Crohn’s disease, and ulcerative colitis when other treatments haven’t worked. It’s approved for adults and children 13 and older. Like loperamide, it should not be used when bloody diarrhea or fever is present.
Antibiotics for Traveler’s Diarrhea
Antibiotics are not a first-line treatment for most diarrhea, but they play a specific role in traveler’s diarrhea that’s moderate or severe. CDC guidelines define moderate as diarrhea that’s distressing or interferes with your plans, and severe as diarrhea that’s incapacitating. Mild cases (tolerable, not interfering with activities) don’t warrant antibiotics at all.
For moderate to severe traveler’s diarrhea, azithromycin and fluoroquinolones are the most commonly prescribed options. Rifaximin is another choice, approved for diarrhea caused by non-invasive strains of E. coli in patients 12 and older. It’s not effective against invasive bacteria like Salmonella, Shigella, or Campylobacter, so it’s only appropriate when there’s no blood in the stool and no high fever. Prophylactic antibiotics (taking them before you get sick) are discouraged for most travelers.
What About Probiotics?
Probiotics are widely marketed for digestive health, but the evidence for treating active diarrhea is weak. A large Cochrane review found no meaningful difference between probiotic and control groups in how long diarrhea lasted or in the chance of diarrhea continuing beyond 48 hours. The American Gastroenterological Association recommended against using probiotics for acute infectious diarrhea in children in the US and Canada. Some European guidelines have suggested two specific strains (Saccharomyces boulardii and Lactobacillus rhamnosus GG), but acknowledged that the supporting evidence was low-quality. Probiotics are unlikely to cause harm, but they shouldn’t be relied on as a primary treatment.
Diarrhea Medicine and Children
Antidiarrheal medications, including both loperamide and bismuth subsalicylate, are not recommended for infants or young children. The risks outweigh any benefit. In children, these medicines can mask worsening symptoms and delay treatment for serious infections. Loperamide in particular can worsen certain types of diarrhea in young kids.
For children, the priority is preventing dehydration. Oral rehydration solutions are the cornerstone of treatment. Small, frequent sips work better than large amounts at once, especially if the child is also vomiting. Most episodes of childhood diarrhea resolve on their own within a few days. If a child has bloody stool, persistent vomiting, signs of dehydration (no tears when crying, no wet diapers for several hours, sunken eyes), or diarrhea lasting more than a few days, that warrants prompt medical evaluation rather than over-the-counter treatment.