What Do Doctors Prescribe for Severe Diarrhea?

October 14, 2025 •

4 min read

While most acute diarrhea resolves on its own, severe cases can lead to serious dehydration and require medical intervention. When faced with severe diarrhea, healthcare providers may prescribe specific medications tailored to the underlying cause, whether it is an infection, a chronic condition like IBS-D, or traveler's diarrhea.

Quick Summary

Treatment for severe diarrhea depends on the cause and may involve prescription medications. Rehydration is the primary step, followed by targeted therapies such as antibiotics for bacterial infections or specific drugs for chronic conditions like IBS-D.

Key Points

Initial Step: The priority for severe diarrhea is supportive care, focusing on fluid and electrolyte replacement through oral rehydration solutions or IV fluids for severe dehydration.
Infectious Causes: Antibiotics like azithromycin, rifaximin, or metronidazole are prescribed for specific bacterial infections, but are not for viral gastroenteritis.
Chronic Conditions: For severe diarrhea from chronic illnesses like IBS-D, specialized prescription medications such as alosetron, eluxadoline, and bile acid binders may be used.
Cautious Use of Antidiarrheals: Antidiarrheal agents like loperamide should be avoided in cases of bloody stool, high fever, or inflammatory diarrhea, as they can worsen the condition.
Medical Guidance is Essential: A correct diagnosis is critical, as treatment for severe diarrhea is highly dependent on its specific cause. Always consult a healthcare professional.

The medical management of severe diarrhea is not a one-size-fits-all approach. The treatment strategy depends heavily on the root cause of the condition, which can range from infectious pathogens to underlying chronic diseases. For this reason, diagnosis by a healthcare professional is crucial before initiating any treatment plan involving prescription medications. The first and most critical step, regardless of the cause, is supportive care focused on replacing lost fluids and electrolytes.

Supportive Care and Hydration

Severe diarrhea, especially in vulnerable populations like children and the elderly, can quickly lead to life-threatening dehydration. Therefore, fluid and electrolyte replacement is the cornerstone of initial treatment. Oral rehydration solutions (ORS) are preferred for mild to moderate dehydration. These solutions, containing precise amounts of salts and sugars, help the intestines absorb fluids more effectively. In cases of severe dehydration, vomiting, or shock, intravenous (IV) fluid administration is necessary.

Oral Rehydration vs. IV Rehydration

Oral Rehydration: For most cases of acute diarrhea, ORS can be administered in small, frequent amounts. Commercial preparations like Pedialyte are available, while the World Health Organization (WHO) provides a recipe for a low-osmolarity solution.
Intravenous Rehydration: In emergency situations involving severe dehydration or shock, IV therapy with isotonic saline is required to rapidly restore fluid balance.

Pharmacological Approaches for Severe Diarrhea

Once supportive care is in place, specific pharmacological interventions can address the underlying cause of the diarrhea. A doctor's prescription is often needed for these targeted therapies.

Antibiotics for Infectious Diarrhea

Antibiotics are reserved for diarrhea caused by specific bacterial or parasitic infections, and are not appropriate for most viral cases.

Rifaximin (Xifaxan): This is a minimally-absorbed antibiotic used to treat traveler's diarrhea caused by non-invasive E. coli and is also effective for diarrhea related to irritable bowel syndrome (IBS-D).
Azithromycin: Often prescribed for moderate to severe traveler's diarrhea, particularly in regions with high fluoroquinolone resistance, and for cases involving pathogens like Campylobacter.
Metronidazole (Flagyl): Used to treat specific bacterial infections, including those caused by C. difficile, and parasitic infections like Giardia.
Fidaxomicin (Dificid): A macrolide antibiotic specifically indicated for C. difficile-associated diarrhea.

Antidiarrheal Agents

Antimotility agents, such as loperamide, can provide symptomatic relief but must be used with caution, especially in infectious cases.

Loperamide (Imodium): Slows intestinal movement and increases water reabsorption. While available over-the-counter (OTC), higher doses may be prescribed for severe or chronic diarrhea under medical supervision. It is typically avoided in cases of bloody or inflammatory diarrhea due to the risk of complications.
Diphenoxylate/Atropine (Lomotil): A prescription combination drug that also decreases gut motility.

Medications for Chronic Diarrhea (IBS-D, etc.)

For severe diarrhea resulting from chronic conditions, treatment focuses on managing the underlying disease.

Alosetron (Lotronex): A serotonin (5-HT3) receptor antagonist reserved for women with severe IBS-D that has not responded to conventional therapy, due to risks of serious side effects.
Eluxadoline (Viberzi): An opioid receptor agonist/antagonist used for IBS-D to help regulate bowel movements and abdominal pain.
Bile Acid Binders (e.g., Cholestyramine): Used for diarrhea caused by bile acid malabsorption, which can occur after surgery or in some cases of functional diarrhea.
Other Agents: For conditions like microscopic colitis, drugs such as budesonide may be prescribed.

Medication Comparison for Severe Diarrhea


Medication Class	Examples	Typical Use Case	Key Considerations
Antimotility Agents	Loperamide, Diphenoxylate/Atropine	Symptomatic relief for watery, non-infectious diarrhea	Avoid in bloody/inflammatory diarrhea; risk of toxic megacolon
Antibiotics	Rifaximin, Azithromycin, Metronidazole	Bacterial/parasitic infections (e.g., traveler's diarrhea, C. diff)	Avoid if viral cause; resistance is a concern for some drugs
Bile Acid Binders	Cholestyramine	Chronic diarrhea due to bile acid malabsorption	Can cause side effects like bloating and constipation; poor palatability
IBS-D Specific	Alosetron, Eluxadoline	Severe diarrhea-predominant Irritable Bowel Syndrome	Restricted use for Alosetron due to serious risks; Eluxadoline has fewer side effects
Anti-Inflammatory	Budesonide	Microscopic Colitis	Used when inflammatory conditions are the cause

Conclusion

While many cases of diarrhea are mild and self-limiting, severe episodes require a more proactive approach, beginning with immediate rehydration and potentially progressing to prescription medications. The specific drug a doctor prescribes is not random but is carefully chosen based on the underlying cause. Antibiotics are reserved for confirmed or suspected bacterial infections, while specific antidiarrheals and other agents address conditions like IBS-D or bile acid malabsorption. It is imperative that individuals with severe diarrhea, especially with fever, bloody stool, or signs of dehydration, seek medical attention. Self-treating with high-dose OTC medications can be dangerous and may mask an underlying, more serious condition. The correct diagnosis is the first step toward effective and safe treatment.

This information is for informational purposes only and does not constitute medical advice. Consult a healthcare provider for a proper diagnosis and treatment plan.

Frequently Asked Questions

The first treatment for severe diarrhea is rehydration. A doctor will focus on replacing lost fluids and electrolytes, usually with an oral rehydration solution (ORS). In cases of severe dehydration, intravenous (IV) fluids may be necessary.

Doctors prescribe antibiotics only when there is a confirmed or suspected bacterial or parasitic cause for the diarrhea. They are not effective for viral gastroenteritis, which is the most common cause of acute diarrhea.

While loperamide is available OTC, its use for severe diarrhea should be approached with caution. It is especially risky if you have bloody diarrhea or a high fever, as it can worsen some infectious conditions. Always consult a doctor before using it for a severe or infectious case.

For severe Irritable Bowel Syndrome with Diarrhea (IBS-D), doctors might prescribe specialized medications like alosetron, eluxadoline, or the antibiotic rifaximin. These target specific mechanisms related to the chronic condition.

For severe traveler's diarrhea, a doctor may prescribe antibiotics such as azithromycin, ciprofloxacin, or rifaximin to shorten the duration and severity of the illness. Supportive care with rehydration is also crucial.

It is important to see a doctor for severe diarrhea because a proper diagnosis is needed to ensure the correct treatment. A doctor can determine if the cause is bacterial, parasitic, or from a chronic condition and prescribe the most appropriate, and safest, medication.

Treatment for C. difficile infection, a serious cause of severe diarrhea, typically involves specific antibiotics like oral vancomycin or fidaxomicin. Standard antidiarrheal medications like loperamide are generally avoided.