For most adults with diarrhea and vomiting, a combination of loperamide (Imodium) for diarrhea and an oral rehydration solution to replace lost fluids is the most effective starting point. If vomiting is severe enough to prevent you from keeping fluids down, ondansetron (Zofran) is the most reliably effective anti-nausea medication, though it requires a prescription in the United States. The right approach depends on what’s causing your symptoms, how severe they are, and whether you’re treating an adult or a child.
Best Medications for Diarrhea
Loperamide is the go-to over-the-counter option for acute diarrhea in adults and teens 13 and older. It works by slowing the movement of your intestines, giving your body more time to absorb water from stool. The standard adult dose is two tablets (4 mg) after your first loose bowel movement, then one tablet (2 mg) after each subsequent one. The maximum is 8 tablets (16 mg) in 24 hours for capsules, or 4 tablets (8 mg) in 24 hours for the tablet form.
Bismuth subsalicylate (Pepto-Bismol) is another over-the-counter choice that can address both diarrhea and nausea at the same time. It’s gentler than loperamide but also less powerful for stopping diarrhea on its own. Many people find it helpful for mild cases, especially when nausea is the more bothersome symptom.
When Not to Take Loperamide
Loperamide is safe for ordinary stomach bugs, but there are specific situations where it can make things worse. The FDA labels it as contraindicated when diarrhea involves blood in the stool, high fever, or a known bacterial infection from organisms like Salmonella, Shigella, or Campylobacter. In those cases, slowing your intestines down traps the infectious agent inside longer.
If your diarrhea hasn’t improved within 48 hours of taking loperamide, stop using it and get medical evaluation. Persistent diarrhea with blood, fever, or significant abdominal bloating warrants prompt attention.
Best Medications for Vomiting
Over-the-counter antihistamines like dimenhydrinate (Dramamine) and meclizine can take the edge off nausea, but they’re designed more for motion sickness than for the kind of vomiting that comes with a stomach virus. For gastroenteritis, the most effective anti-vomiting medication is ondansetron, which blocks the serotonin signals that trigger your vomiting reflex. A systematic review found it reduces vomiting, hospitalization, and the need for IV fluids. Standard prescription anti-nausea drugs like metoclopramide and prochlorperazine also work, but ondansetron consistently outperforms them in studies. Metoclopramide at its standard 10 mg dose performs no better than placebo for some types of nausea.
If you can’t get a prescription, bismuth subsalicylate is your best OTC option for nausea from a stomach bug. Ginger supplements or ginger tea can also provide modest relief, though the evidence is stronger for pregnancy-related nausea than for gastroenteritis.
Rehydration Matters More Than Medication
The biggest risk from combined diarrhea and vomiting isn’t the symptoms themselves. It’s dehydration. When you’re losing fluid from both ends, your body can fall behind quickly. An oral rehydration solution (like Pedialyte, DripDrop, or a WHO-formula ORS) replaces not just water but the sodium, potassium, and glucose your body needs to actually absorb that water. Plain water, soda, chicken broth, and apple juice don’t do this well. They can even worsen the problem because their sugar and salt ratios pull water into the intestines rather than out of them, potentially causing low sodium levels.
Take small, frequent sips rather than large gulps, especially if you’re still vomiting. Even a tablespoon every few minutes adds up and is less likely to trigger another round of vomiting than drinking a full glass at once.
Signs of dehydration to watch for: urinating much less than usual, a rapid heart rate, dry mouth, and skin that stays “tented” (doesn’t flatten back immediately) when you pinch it. In infants, no wet diapers for three hours is a red flag.
The BRAT Diet Is Outdated
You’ve probably heard that bananas, rice, applesauce, and toast are what you should eat when you have a stomach bug. This advice has been around for decades, but clinical trials now show the opposite approach works better. Returning to your normal diet as soon as you can tolerate food leads to lower stool output, shorter illness, and better nutritional recovery compared to restricting yourself to bland foods. Sticking to only BRAT foods can actually impair your recovery and, in prolonged illness, lead to nutritional deficiencies. Eat what sounds tolerable from a variety of sources. If that happens to be toast and bananas, fine, but don’t limit yourself to them.
Probiotics Can Shorten the Illness
Certain probiotic strains, particularly Lactobacillus rhamnosus GG, have solid evidence behind them for shortening diarrhea. A meta-analysis found that this strain reduced the duration of diarrhea by about 24 hours on average, with even larger reductions (around 31 hours) for diarrhea caused by rotavirus. The effective dose in studies was at least 10 billion colony-forming units per day. Probiotics work best when started early and combined with proper rehydration. They won’t stop vomiting or diarrhea immediately, but they can meaningfully cut the total time you’re sick.
Treating Children Is Different
Kids need a more cautious approach. The American Academy of Family Physicians advises against most antidiarrheal medications in children because they delay the body’s clearance of the infection. Loperamide specifically is not recommended for children under two, and older children face risks of excessive sedation and constipation.
For vomiting in children, ondansetron is the only antiemetic generally considered appropriate, and it’s typically reserved for situations where a child can’t keep down enough fluid to stay hydrated. Other anti-nausea medications carry too many side effects for pediatric use. The primary treatment for children is oral rehydration with a pediatric ORS (not an adult formulation, and not juice or soda). Probiotics given alongside rehydration can help reduce the duration of diarrhea in children, with strong evidence supporting this combination.
What to Expect for Recovery
Most viral gastroenteritis, the common “stomach flu,” resolves on its own within one to three days. Vomiting typically stops first, often within 12 to 24 hours, while diarrhea can linger for a few days longer. If vomiting lasts more than 24 hours in an adult, diarrhea persists beyond 48 hours without improvement, or you notice blood in your stool, a fever over 102°F, or signs of dehydration, those are signals that something beyond a simple stomach bug may be going on and medical evaluation is warranted.