What medication stops liquid diarrhea?: A Guide to OTC and Prescription Treatments

October 14, 2025 •

4 min read

Acute diarrhea is one of the most common illnesses, with adults experiencing an average of one episode per year. Fortunately, several over-the-counter (OTC) and prescription options can effectively manage and stop liquid diarrhea, with the best choice depending on the underlying cause.

Quick Summary

Liquid diarrhea can often be managed with over-the-counter medications such as loperamide or bismuth subsalicylate, which work by slowing gut motility or balancing intestinal fluids. For severe cases or underlying conditions, prescription antibiotics or other specific drugs may be necessary. Supportive care, including proper hydration, is crucial for recovery.

Key Points

Loperamide (Imodium): An OTC medication that slows intestinal movement, making it effective for reducing the frequency of loose stools.
Bismuth Subsalicylate (Pepto-Bismol): An OTC option that helps balance fluids in the digestive tract and reduces intestinal inflammation for milder cases of diarrhea.
Prescription for Severe Cases: If diarrhea is severe, bloody, or persistent, a doctor may prescribe antibiotics or specific medications, particularly for bacterial infections or conditions like IBS-D.
Hydration is Crucial: Replacing lost fluids and electrolytes is the most important supportive treatment, often through oral rehydration solutions, broth, or water.
Dietary Adjustments Aid Recovery: Sticking to bland, low-fiber foods (like the BRAT diet) and avoiding irritants like caffeine and fatty foods can help the digestive system heal.
Know When to See a Doctor: Seek medical attention for diarrhea lasting more than two days, or if you experience fever, severe abdominal pain, or blood in your stool.
Probiotics Can Help Restore Balance: Specific probiotic strains, such as Lactobacillus rhamnosus GG and Saccharomyces boulardii, may help restore gut flora and shorten the duration of diarrhea.

Diarrhea, particularly its liquid form, can be a disruptive and dehydrating condition. While many cases resolve on their own, over-the-counter (OTC) medications can provide significant and rapid symptom relief. The most common OTC options are loperamide and bismuth subsalicylate, both of which work differently to provide relief. For more severe, persistent, or infection-related cases, a healthcare provider may need to intervene with prescription-strength medications.

Over-the-Counter Medications for Liquid Diarrhea

Loperamide (Imodium)

Loperamide is one of the most widely used OTC anti-diarrheal medications. It works by acting directly on the muscles of the intestine to slow down the movement of food and waste. This allows the body more time to absorb water from the intestinal tract, resulting in less frequent and more solid stools.

How it works: Slows intestinal contractions and reduces the speed at which waste passes through the gut.
Who it's for: Adults and children over 6 years old with acute or traveler's diarrhea. Higher doses may be prescribed for chronic conditions.
Potential side effects: Can include dizziness, drowsiness, dry mouth, and constipation. Serious heart problems can occur if more than the recommended dose is taken.

Bismuth Subsalicylate (Pepto-Bismol, Kaopectate)

Bismuth subsalicylate provides multi-symptom relief for digestive issues, including diarrhea, upset stomach, and gas. It is most effective for milder cases and works through several mechanisms.

How it works: It decreases inflammation within the intestine, inhibits intestinal secretions, and may kill some of the organisms that cause diarrhea, including certain bacteria.
Who it's for: Adults and children over 12 years old for occasional diarrhea and upset stomach. It is also used to help prevent traveler's diarrhea.
Potential side effects: Can cause a harmless, temporary blackening of the tongue and stool. Should be used with caution in those who are allergic to salicylates like aspirin.

Comparison of Loperamide vs. Bismuth Subsalicylate


Feature	Loperamide (Imodium)	Bismuth Subsalicylate (Pepto-Bismol/Kaopectate)
Primary Mechanism	Slows intestinal motility and allows for increased water absorption.	Reduces fluid secretion, lowers inflammation, and has antimicrobial effects.
Speed of Action	Often works within an hour to reduce stool frequency.	Provides relief from a range of symptoms, with effects often seen within a few hours.
Best For	Quickly stopping acute, non-bloody, watery diarrhea.	Multi-symptom relief including upset stomach, heartburn, and mild diarrhea.
Notable Side Effect	Dizziness and drowsiness; serious heart issues with overdose.	Harmless darkening of tongue and stool.
Consideration	Avoid in cases of fever or bloody diarrhea.	Use caution with other salicylate products (aspirin) and in those with bleeding issues.

Prescription Medications and When They Are Needed

Not all cases of liquid diarrhea can or should be treated with OTC products. In some situations, a doctor's diagnosis and prescription are required, especially for severe or chronic conditions.

Antibiotics and Antiparasitics

If the diarrhea is caused by a bacterial or parasitic infection, such as traveler's diarrhea or C. difficile infection, a doctor may prescribe an antibiotic or antiparasitic. Rifaximin (Xifaxan) is an antibiotic that specifically works in the gut to treat certain types of bacterial diarrhea, including IBS-D and traveler's diarrhea.

Other Prescriptions

For chronic diarrhea related to conditions like Irritable Bowel Syndrome with Diarrhea (IBS-D), a doctor may prescribe medications that specifically target gut contractions, such as eluxadoline (Viberzi). These are typically reserved for severe cases that haven't responded to other treatments.

Supportive Care for Diarrhea

Regardless of the medication used, supportive care is vital for a quick recovery and to prevent complications, particularly dehydration.

Stay Hydrated: Drink plenty of clear fluids, including water, broth, and oral rehydration solutions (ORS) to replace lost fluids and electrolytes.
Adopt a Bland Diet: Follow the BRAT diet (Bananas, Rice, Applesauce, Toast) for a short period. These low-fiber, binding foods can help firm up stools.
Avoid Irritants: Steer clear of fatty, greasy, spicy, and high-fiber foods, as well as caffeine and alcohol, which can worsen symptoms.

The Role of Probiotics

Probiotics are beneficial microorganisms that can help restore a healthy balance of bacteria in the gut, which can be disrupted by illness or antibiotics. While research is ongoing, some strains, such as Lactobacillus rhamnosus GG (LGG) and Saccharomyces boulardii, have shown promise in reducing the duration of certain types of diarrhea, including antibiotic-associated and traveler's diarrhea.

Conclusion

For most mild to moderate cases, over-the-counter medications like loperamide and bismuth subsalicylate are effective treatments for liquid diarrhea. Loperamide is a potent motility inhibitor, while bismuth subsalicylate offers broader relief for an upset stomach. It is crucial to stay hydrated and follow dietary modifications to support recovery. However, if diarrhea is accompanied by fever, blood in the stool, or persists for more than two days, it is essential to consult a healthcare provider to determine if an underlying infection or chronic condition requires prescription medication.

Frequently Asked Questions

For mild cases, over-the-counter medication like loperamide (Imodium) can work within an hour to reduce the frequency of loose stools. Staying well-hydrated and consuming bland foods like the BRAT diet can also help speed up recovery.

No. You should not take anti-diarrheal medication if you have a fever, bloody stool, or suspect a bacterial infection, as it can worsen the condition by preventing your body from clearing the infection. In these cases, consult a healthcare provider.

Loperamide slows down the movement of the intestines, while bismuth subsalicylate balances how fluid moves through the digestive tract and has anti-inflammatory and antibacterial properties. Loperamide is more focused on reducing the number of bowel movements, while bismuth subsalicylate provides broader symptom relief.

Over-the-counter anti-diarrheal medications are generally not recommended for young children unless a pediatrician advises it. The primary focus for children is preventing dehydration with oral rehydration solutions like Pedialyte.

Certain probiotic strains, such as Saccharomyces boulardii and Lactobacillus rhamnosus GG, have been shown to help shorten the duration of diarrhea, particularly when it's associated with antibiotics or travel. They work by restoring the gut's natural bacterial balance.

You should see a doctor if your diarrhea lasts more than two days, if you have severe abdominal pain, fever, bloody or black stool, or show signs of dehydration like dizziness or reduced urination.

Focus on a bland, low-fiber diet like the BRAT diet (bananas, white rice, applesauce, toast). As your symptoms improve, you can slowly reintroduce other easily digestible foods like plain noodles, potatoes, and lean chicken.