Most cases of diarrhea in healthy adults resolve on their own within a few days, but over-the-counter medications can reduce symptoms and get you back to normal faster. The two main options available without a prescription are loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol), and each works differently depending on the type of diarrhea you’re dealing with.
Loperamide: The Go-To for Slowing Things Down
Loperamide works by slowing down the movements of your intestines, giving your body more time to absorb water and firm up your stool. It also has some anti-secretory properties, meaning it reduces the amount of fluid your intestines release. The standard adult dose is 4 mg (two capsules or tablets) after the first loose bowel movement, then 2 mg after each additional loose stool. The maximum is 16 mg in 24 hours for capsules, or 8 mg for the over-the-counter tablet form.
Loperamide is effective for garden-variety loose stools, traveler’s diarrhea, and chronic conditions like irritable bowel syndrome. However, you should not use it if you have a fever or bloody stools. In those cases, your body may be fighting a bacterial infection, and slowing your gut can actually make things worse by keeping the pathogen inside longer.
Bismuth Subsalicylate: Best for Stomach Bugs
Bismuth subsalicylate, sold as Pepto-Bismol, takes a different approach. It has antibacterial properties that work against the germs causing infectious diarrhea, while also reducing inflammation and excess fluid secretion in the intestinal lining. It can even bind to toxins produced by certain bacteria. This makes it a solid choice when diarrhea comes with nausea or an upset stomach, which is why it’s also popular for traveler’s diarrhea. Studies in Mexico found it reduced traveler’s diarrhea incidence by roughly 50% when used preventively.
The tradeoff is a longer list of people who shouldn’t take it. Bismuth subsalicylate contains a compound related to aspirin, so it’s off-limits if you have an aspirin allergy, take blood thinners like warfarin, or use medications for gout. Don’t combine it with aspirin either, as the overlapping ingredients raise the risk of salicylate toxicity, which can show up as ringing in your ears or easy bruising. Pregnant and breastfeeding women should also avoid it. For children and teenagers recovering from flu or chickenpox, bismuth subsalicylate carries a risk of Reye’s syndrome, a rare but serious condition. The CDC does not recommend it for children under 12, and some guidelines extend caution up to age 18 during viral illnesses.
Probiotics: Helpful but Not All the Same
Probiotics can shorten a bout of infectious diarrhea by about 30 hours on average, based on a large Cochrane review of clinical trials. They also reduce the likelihood that diarrhea persists past three days by roughly a third. That said, not every probiotic product on the shelf will do this. The benefits are strain-specific, meaning what works for one bacterial strain cannot be assumed to work for another.
The strains with the most evidence behind them include Lactobacillus casei GG (often labeled Lactobacillus rhamnosus GG), which appears particularly effective for diarrhea caused by rotavirus, and Enterococcus LAB strain SF68. A combination of Lactobacillus acidophilus and Lactobacillus bifidus also showed strong results in smaller studies. If you’re buying a probiotic specifically for diarrhea, check the label for these strains rather than grabbing a general-purpose product.
Prescription Options for Chronic Diarrhea
If diarrhea is a recurring problem rather than a one-time event, the conversation shifts to prescription medications. For people with irritable bowel syndrome with diarrhea (IBS-D), the American Gastroenterological Association recommends two main options: rifaximin, a gut-targeted antibiotic that can be repeated if symptoms return after an initial response, and eluxadoline, which slows gut contractions and fluid secretion. Eluxadoline isn’t appropriate for everyone. It’s contraindicated if you’ve had your gallbladder removed or if you drink more than three alcoholic beverages a day.
For infectious diarrhea with fever or blood in the stool, a doctor may prescribe antibiotics targeting specific bacteria like Salmonella, Shigella, or Campylobacter. Most acute diarrhea episodes in otherwise healthy people are viral or have no identifiable cause and don’t need antibiotics at all.
Traveler’s Diarrhea: A Special Case
If you’re traveling internationally and develop diarrhea, the most effective approach combines loperamide with a short course of antibiotics. A single dose of an antibiotic is often just as effective as a three-day course, which makes it more practical when you’re on the go. If symptoms don’t improve within 24 hours, you can extend to a full three-day regimen. Preventive antibiotics before a trip aren’t recommended for most travelers, though doctors may consider them for immunocompromised individuals.
For prevention without antibiotics, bismuth subsalicylate taken during travel cuts your risk roughly in half, though you need to weigh that against the contraindications listed above. The basics still matter too: stick to bottled water, avoid ice, and be cautious with street food.
Signs That Diarrhea Needs More Than Medicine
In adults, diarrhea lasting more than two days without any improvement, severe abdominal or rectal pain, or more than 10 bowel movements a day warrants medical evaluation. The same goes for signs of dehydration like dark urine, dizziness, or dry mouth. For children, the timeline is shorter: see a doctor if diarrhea hasn’t improved within 24 hours, if there’s a fever above 102°F (39°C), or if stools are bloody or black.
Staying hydrated matters more than any medication during a diarrhea episode. Water alone won’t replace the electrolytes you’re losing, so oral rehydration solutions or drinks with sodium and potassium are a better choice, especially for children or older adults who dehydrate more quickly.