Diarrhea treatment
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Diarrhea: Treatment
Overview
Diarrhea is classified as acute (< 14 days) or chronic/persistent (> 14 days). Acute infectious diarrhea is extremely common - globally, it accounts for over 1.6 million deaths/year, with half a million in children under 5. Treatment is directed at: (1) preventing/treating dehydration, (2) replacing ongoing losses, and (3) meeting nutritional needs. Most acute cases are self-limiting and do not require antibiotics.
1. Rehydration - The Foundation
Oral Rehydration Therapy (ORT)
ORT is the cornerstone of treatment for mild-to-moderate dehydration and should be the first-line approach in almost all cases.
ORS composition - commercially available sachets (sodium, glucose, potassium, citrate/bicarbonate in water). A basic home formulation: ½ tsp salt + 6 level tsp sugar in 1 litre of clean water.
Volume calculation (Rosen's/Tintinalli's):
- Mild dehydration (3-5%): 30-50 mL/kg over 4 hours
- Moderate dehydration (6-9%): 60-80 mL/kg over 4 hours
- Administer 25% of total volume per hour
- Replace ongoing losses: 10 mL/kg per diarrheal stool, 2 mL/kg per vomiting episode
Low-osmolarity ORS (<270 mOsm/L) is preferred. ORT can be started even if the patient continues to vomit.
Zinc supplementation: In children in low-income regions, zinc sulfate (10 mg/day for children < 6 months; 20 mg/day for children > 6 months) reduces the duration, severity, and recurrence of diarrhea. This is now a WHO/UNICEF recommendation. - Goldman-Cecil Medicine, p. 2973
Intravenous Hydration
Reserved for:
- Severe dehydration / shock
- Inability to tolerate oral fluids
- Lethargy, acute abdomen, suspected obstruction
- Failed ORT trial (4-8 hours)
Severe dehydration: 20 mL/kg of 0.9% normal saline (or isotonic crystalloid) IV/IO; repeat boluses until clinical improvement. Use Ringer's lactate or normal saline + ORS as tolerated. - Rosen's Emergency Medicine, p. 3245
2. Diet
- Do NOT fast. Routine fasting is not recommended.
- Resume an age-appropriate diet early (including breastfeeding for infants).
- Avoid high-sugar drinks (sports beverages, juices) in young children as they can worsen osmotic diarrhea.
- For mild dehydration in children 6-60 months, dilute apple juice followed by preferred fluids is an acceptable alternative to ORS. - Rosen's EM, p. 3247
3. Symptomatic / Antimotility Agents
For mild-to-moderate watery diarrhea without fever or bloody/mucoid stools:
| Agent | Dose | Notes |
|---|---|---|
| Loperamide | 4 mg initially, then 2 mg after each loose stool; max 16 mg/day | Opioid receptor agonist; reduces motility and secretion. Avoid with bloody diarrhea, fever, or mucoid stools. |
| Bismuth subsalicylate | 524 mg (liquid or tablet) q30-60 min as needed; max 4200 mg/day (8 doses) | Safe and effective for bacterial diarrheas; also reduces nausea. Can cause black tongue/stool. |
Warning: Antimotility agents like loperamide are contraindicated in bloody diarrhea (dysentery), suspected invasive infection (Shigella, C. difficile), or children with severe colitis, as they can prolong illness, worsen toxin exposure, and increase risk of toxic megacolon. - Tintinalli's Emergency Medicine, p. 888; Goldman-Cecil Medicine, p. 2973
Racecadotril (acetorphan): An enkephalinase inhibitor acting on the enteric nervous system - reduces secretion without affecting motility. Useful in children and adults. - Goldman-Cecil Medicine
4. Antibiotic Therapy
When Are Antibiotics Indicated?
Antibiotics are NOT routinely recommended for most acute watery diarrhea. Most bacterial diarrhea resolves spontaneously. Antibiotics are indicated for:
- Dysentery (bloody/mucoid stool with fever)
- Cholera (severe watery diarrhea with rapid volume depletion)
- Severe illness in immunocompromised patients
- Traveler's diarrhea (moderate-to-severe)
- Persistent diarrhea (> 2 weeks) with identified pathogen
Empiric Antibiotic Regimens
From Goldman-Cecil Medicine, Table 26-5:
| Indication | Antibiotic | Dose |
|---|---|---|
| Acute bacterial diarrhea (empiric) | Azithromycin | 1 g single dose PO, OR 500 mg/day × 3 days |
| Acute bacterial diarrhea (empiric) | Ciprofloxacin | 500 mg PO q12h × 3 days |
| Traveler's diarrhea (non-invasive) | Rifaximin | 200 mg PO three times daily × 3 days |
| Traveler's diarrhea | Azithromycin | 1000 mg PO single dose |
| Traveler's diarrhea | Levofloxacin | 500 mg PO once daily × 3 days |
Note: Fluoroquinolone resistance is widespread in many geographic areas. Azithromycin is generally preferred, especially for Campylobacter. - Harrison's Principles of Internal Medicine 22E
Pathogen-Specific Antibiotics
- Shigella: Azithromycin or ciprofloxacin (resistance-guided); antibiotics reduce duration of fever, diarrhea, and shedding. - Goldman-Cecil Medicine, p. 2252
- Cholera (V. cholerae): Azithromycin single dose (first-line), or doxycycline
- C. difficile: Stop offending antibiotic; vancomycin PO or fidaxomicin is first-line
- Giardia: Metronidazole 250 mg TID × 5-7 days, or tinidazole single dose
- E. coli EPEC: Most infections self-limiting; supportive care only in most cases
- Salmonella (non-typhoidal): Antibiotics only for severe/invasive disease or high-risk patients (immunocompromised, extremes of age); ciprofloxacin or azithromycin
5. Traveler's Diarrhea - Self-Treatment Algorithm
From Harrison's Principles of Internal Medicine 22E:
| Severity | Management |
|---|---|
| Mild (not distressing, no impact on activities) | Increase oral fluids; loperamide or bismuth subsalicylate |
| Moderate (distressing, may interfere with activities) | Loperamide + consider antibiotics (azithromycin or rifaximin) |
| Severe / dysentery (incapacitating, bloody stool, fever) | Antibiotics (azithromycin preferred); avoid loperamide |
6. Special Populations
Children
- ORS is first-line; low-osmolarity formulations preferred
- Zinc supplementation (20 mg/day for children > 6 months) for 10-14 days - WHO/UNICEF guidelines
- Ondansetron (0.15 mg/kg IV/IM) or oral is effective for vomiting to facilitate ORT
- Do not restrict diet; continue breastfeeding
- Rotavirus vaccination has significantly reduced pediatric diarrhea hospitalizations
Elderly / Immunocompromised
- Lower threshold for IV rehydration and antibiotic use
- Higher risk of bacteremia from non-typhoidal Salmonella
Pregnancy
- ORS preferred; antibiotics only when clearly indicated
- Avoid fluoroquinolones; azithromycin is generally safe
7. When to Seek Emergency Care / Hospitalization
- Signs of severe dehydration (sunken eyes, dry mucous membranes, decreased urine output, altered mental status)
- Bloody/mucoid diarrhea with high fever
-
10 stools in 24 hours
- Inability to tolerate oral fluids
- Duration > 14 days
- Age extremes (newborns, elderly) or immunocompromised
- Suspected cholera (rice-water stool)
Summary Table
| Treatment Category | First-Line Approach |
|---|---|
| Mild dehydration | ORS 30-50 mL/kg over 4 hours |
| Moderate dehydration | ORS 60-80 mL/kg over 4 hours |
| Severe dehydration | IV NS 20 mL/kg bolus (repeat prn) |
| Symptom relief (watery, no fever) | Loperamide or bismuth subsalicylate |
| Zinc (children) | 20 mg/day × 10-14 days |
| Empiric antibiotics (severe/traveler's) | Azithromycin (preferred) or ciprofloxacin |
| Non-invasive traveler's diarrhea | Rifaximin 200 mg TID × 3 days |
Sources:
- Goldman-Cecil Medicine International Edition (2-volume set), Table 26-5 and Chapter 285
- Rosen's Emergency Medicine: Concepts and Clinical Practice, Chapter 167
- Tintinalli's Emergency Medicine: A Comprehensive Study, Chapter 131
- Harrison's Principles of Internal Medicine, 22nd Edition (2025), Chapter 130
- WHO/UNICEF Diarrhoea Treatment Guidelines
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