For most adults with acute diarrhea, loperamide (sold as Imodium) is the most effective over-the-counter medicine. It works by slowing intestinal movement, which gives your body more time to absorb water and firm up stools. Bismuth subsalicylate (Pepto-Bismol) is a solid second choice that works differently and can also help with nausea. But the “best” option depends on what’s causing your diarrhea, how severe it is, and whether you’re treating an adult or a child.
Loperamide: The Go-To for Fast Relief
Loperamide slows down the muscles in your intestines, reducing the frequency of loose stools. For acute diarrhea, the standard adult dose is 4 mg (two capsules or tablets) after your first loose bowel movement, then 2 mg after each subsequent one. The daily maximum depends on the formulation: up to 16 mg for capsules, or 8 mg for over-the-counter tablets. Most people notice improvement within a few hours.
Loperamide is best suited for uncomplicated, watery diarrhea, the kind you get from a mild stomach bug, stress, or something you ate. You should avoid it if you have a fever, blood in your stool, or signs of a bacterial infection, because slowing your gut in those situations can trap the pathogen inside and make things worse.
Bismuth Subsalicylate: A Gentler Alternative
Bismuth subsalicylate, the active ingredient in Pepto-Bismol, takes a different approach. Rather than slowing gut motility, it reduces inflammation and excess fluid secretion in the intestinal lining. It also has mild antimicrobial properties, which makes it a reasonable choice for traveler’s diarrhea prevention and mild cases.
The adult dose is two tablets (or two tablespoons of the liquid) every 30 minutes to one hour as needed, up to 16 tablets or 16 tablespoons of regular-strength liquid in 24 hours. It’s not as fast-acting as loperamide for stopping frequent trips to the bathroom, but it handles the broader package of upset stomach, nausea, and diarrhea together. One thing to know: it can temporarily turn your tongue and stool black, which is harmless. Children under 12 should not use it.
When Probiotics Help
Probiotics aren’t a replacement for loperamide when you need quick relief, but they can shorten how long diarrhea lasts, especially in children. The most studied strain is Saccharomyces boulardii CNCM I-745, a beneficial yeast. A meta-analysis in Frontiers in Cellular and Infection Microbiology found it reduced diarrhea duration by roughly 1.5 days on average. The benefit was even larger for rotavirus-related diarrhea, cutting about two days off the illness.
Not all probiotic products are equal. The strain matters, and the dose matters. Look for products that list specific strain names on the label rather than just genus and species. Saccharomyces boulardii and Lactobacillus rhamnosus GG have the strongest evidence behind them. Probiotics are generally safe for most people, though individuals with compromised immune systems should check with a doctor first.
Prescription Options for Traveler’s Diarrhea
If you’re dealing with traveler’s diarrhea caused by bacteria picked up abroad, a doctor may prescribe rifaximin, an antibiotic that works almost entirely inside the gut rather than being absorbed into the bloodstream. The FDA-approved dose is 200 mg three times a day for three days. It’s specifically indicated for non-invasive E. coli infections, which cause the majority of traveler’s diarrhea cases.
Rifaximin is not appropriate if you have a fever, bloody stools, or diarrhea caused by other pathogens. Those symptoms suggest a more invasive infection that needs a different antibiotic or further testing.
What to Eat (and What Not to Restrict)
You’ve probably heard of the BRAT diet: bananas, rice, applesauce, and toast. It’s been recommended for decades, but major health organizations including the American Academy of Pediatrics, the CDC, and the WHO no longer endorse it as a treatment strategy. The reason is straightforward: the BRAT diet is too nutritionally limited. It’s low in protein, fat, fiber, and several essential vitamins and minerals. Sticking to it for more than a meal or two can actually slow recovery by depriving your body of the calories and nutrients it needs to repair the intestinal lining.
The current recommendation is to eat a normal, age-appropriate diet as soon as you can tolerate it. Early nutrition plays a major role in mucosal repair and shortens the duration of illness. You don’t need to force yourself to eat large meals, but there’s no benefit to starving your gut. Plain foods like rice, chicken, potatoes, and cooked vegetables are easy to tolerate without being excessively restrictive. Avoid dairy if it seems to worsen symptoms, and skip greasy, high-sugar, or heavily spiced foods until you feel better.
Hydration Is the Real Priority
Regardless of which medicine you take, replacing lost fluids is the single most important thing you can do. Diarrhea pulls water and electrolytes out of your body quickly, and dehydration is the main reason diarrhea becomes dangerous rather than just uncomfortable. For mild cases, water, broth, and diluted juice work fine. For moderate cases or prolonged diarrhea, oral rehydration solutions (like Pedialyte or store-brand equivalents) replace both water and electrolytes in the right ratio.
Signs of dehydration to watch for include extreme thirst, dark urine, urinating less than usual, dizziness, and fatigue. In infants, warning signs include no wet diapers for three or more hours, no tears when crying, and a sunken soft spot on the skull.
Diarrhea Medicine and Children
The rules are very different for kids. The CDC’s guidelines are clear: antidiarrheal medications, including loperamide, are not recommended for infants and young children. Loperamide can cause serious side effects in small children, including severe abdominal distention and, in rare cases, life-threatening complications. Reports from Pakistan documented 18 cases of severe abdominal distention in children using loperamide, six of which were fatal.
For infants and children, the primary treatment is oral rehydration therapy combined with continued age-appropriate feeding. Oral rehydration solutions are the cornerstone, not anti-diarrheal drugs. If your child has diarrhea lasting more than a day, any fever (in infants) or high fever (in older children), or refuses to eat or drink for more than a few hours, that warrants a call to their pediatrician. Children under 12 months, premature infants, or those with other medical conditions need medical attention sooner rather than later.
Signs That Need Medical Attention
Most diarrhea resolves on its own within a couple of days with fluids and basic over-the-counter treatment. But certain symptoms signal something more serious. Seek care if you notice blood, pus, or black tarry stools. A high fever alongside diarrhea suggests an invasive infection that won’t respond to loperamide alone. Six or more loose stools per day, severe abdominal or rectal pain, frequent vomiting, or any change in mental state like confusion or unusual drowsiness are also reasons to get medical help promptly.
For adults, diarrhea lasting more than two days without improvement is worth a doctor visit. For children, the threshold is lower: one day of persistent diarrhea, especially with other symptoms, should prompt a call.