Treatment of Diarrhea in Adults
For adults with acute diarrhea, the most effective treatment approach is fluid replacement combined with loperamide for symptomatic relief, while maintaining adequate nutrition through small, light meals as tolerated. 1
Initial Assessment and Triage
Determine severity based on:
- Mild to moderate diarrhea: Increased bowel movements without significant dehydration
- Severe diarrhea: Signs of dehydration, high fever (>38.5°C), bloody stools, severe vomiting
Warning signs requiring medical attention:
- High fever (>38.5°C)
- Frank blood in stools
- Severe vomiting preventing oral intake
- Signs of dehydration (decreased urine output, dry mucous membranes, tachycardia)
- Altered mental status
- Persistent symptoms beyond 48-72 hours despite treatment 1
Treatment Algorithm
1. Fluid and Electrolyte Replacement (Priority)
For mild to moderate diarrhea:
- Maintain adequate fluid intake guided by thirst
- Recommended fluids: glucose-containing drinks (lemonade, fruit juices, sweet sodas) or electrolyte-rich soups 1
- Oral rehydration solutions (ORS) are generally not needed for otherwise healthy adults 1
For severe diarrhea with dehydration:
- Intravenous fluids (isotonic saline or balanced salt solution)
- Initial fluid bolus of 20 mL/kg if tachycardic or potentially septic 1
- Monitor fluid balance with target urine output >0.5 mL/kg/h 1
2. Antidiarrheal Medications
First-line agent: Loperamide
- Initial dose: 4 mg (two capsules)
- Followed by 2 mg (one capsule) after each unformed stool
- Maximum daily dose: 16 mg (eight capsules) 2
- Clinical improvement usually observed within 48 hours 2
Caution:
- Avoid loperamide in cases of dysentery (high fever with bloody stools)
- Use with caution in patients with hepatic impairment due to potential increased systemic exposure 2
- Avoid in combination with medications that prolong QT interval due to risk of cardiac adverse reactions 2
3. Dietary Management
- Food intake should be guided by appetite 1
- Small, light meals are recommended
- Avoid fatty, heavy, spicy foods and caffeine (including cola drinks)
- Avoid lactose-containing foods (such as milk) in prolonged episodes 1
4. Antimicrobial Therapy
Antimicrobials are indicated only for:
- Secretory/invasive traveler's diarrhea (quinolones first-line, cotrimoxazole second-line)
- Secretory residential diarrhea when the pathogen is known 1
Note: Empiric antimicrobial use for all acute diarrheal episodes is not recommended due to increasing bacterial resistance 1
Special Considerations
Chronic Diarrhea
- If diarrhea persists beyond 4 weeks, further diagnostic evaluation is warranted 3
- Initial dose for chronic diarrhea is the same as acute (4 mg followed by 2 mg after each unformed stool)
- Average daily maintenance dosage: 4-8 mg (2-4 capsules) 2
- If no improvement after 16 mg/day for 10 days, symptoms are unlikely to respond to further administration 2
Elderly Patients
- No dose adjustment required for elderly patients
- However, elderly may be more susceptible to QT interval prolongation
- Avoid loperamide in elderly taking medications that can prolong QT interval 2
Common Pitfalls to Avoid
Overuse of oral rehydration solutions - While essential for infants and children, ORS are generally not needed for otherwise healthy adults with mild diarrhea 1
Unnecessary dietary restrictions - There is no evidence that fasting or specific diets benefit adults with acute diarrhea 1
Inappropriate use of antimicrobials - Empiric antimicrobial therapy should be reserved for specific indications to prevent increasing bacterial resistance 1
Neglecting fluid replacement - The most critical therapy in diarrheal illness is rehydration with solutions containing water, salt, and sugar 1
Exceeding recommended loperamide dosage - Higher than recommended doses can lead to serious cardiac adverse reactions 2
By following this treatment algorithm, most cases of acute diarrhea in adults will resolve within 48 hours. If symptoms persist or worsen despite appropriate treatment, further medical evaluation is warranted.