What is the recommended treatment and dosing for acute diarrhea, including oral rehydration, anti‑motility agents, and antibiotics when indicated?

Treatment for Diarrhoea with Doses

Oral rehydration solution (ORS) is the single most important intervention for acute diarrhoea, and rehydration must take absolute priority over any other treatment including antibiotics or antimotility agents.

Immediate Rehydration Strategy

Oral Rehydration Solution Dosing by Severity

Mild dehydration (3–5% fluid deficit):

• Administer 50 mL/kg of reduced-osmolarity ORS (containing 75–90 mEq/L sodium) over 2–4 hours 1
• Replace ongoing losses with 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 1
• Reassess hydration status after 2–4 hours 1

Moderate dehydration (6–9% fluid deficit):

• Administer 100 mL/kg of reduced-osmolarity ORS over 2–4 hours 1, 2
• Use the same replacement formula for ongoing losses (10 mL/kg per stool, 2 mL/kg per vomit) 1
• Reassess after 2–4 hours; if still dehydrated, recalculate deficit and restart 3

Severe dehydration (≥10% fluid deficit):

• This is a medical emergency requiring immediate hospitalization 1
• Administer 20 mL/kg IV boluses of lactated Ringer's or normal saline rapidly, repeated until pulse, perfusion, and mental status normalize 1, 2
• After stabilization, transition to ORS to complete remaining deficit replacement 1, 2

Critical Administration Technique

The most common error is allowing rapid, large-volume drinking, which triggers vomiting and falsely suggests ORT failure. 1, 2

• Begin with 5 mL (approximately 1 teaspoon) every 1–2 minutes using a spoon, syringe, or medicine dropper 1, 2
• Gradually increase volume as vomiting diminishes 1
• This slow-administration method achieves >90% success rates in rehydrating patients with vomiting 1, 2
• Nasogastric administration may be used if oral intake is refused but the patient is neurologically intact 3, 2

Antimotility Agents (Loperamide)

Adults (Immunocompetent, Watery Diarrhoea Only)

Loperamide may be used ONLY after adequate rehydration is achieved:

• Initial dose: 4 mg orally 2, 4
• Maintenance: 2 mg after each loose stool 2, 4
• Maximum: 16 mg per 24 hours 2, 5

Absolute Contraindications to Loperamide

Never use loperamide in the following situations:

• All children under 18 years of age – serious adverse events including ileus, respiratory depression, and death have been reported 1, 3, 2
• Bloody diarrhoea or dysentery 2, 4
• Fever ≥38.5°C 2
• Suspected inflammatory or invasive diarrhoea 1, 2
• Risk of toxic megacolon 1

Antibiotic Therapy

When Antibiotics Are NOT Indicated

Routine antibiotics are not recommended for typical acute watery diarrhoea because viral pathogens predominate. 1, 3, 2, 6

When to Use Empiric Antibiotics

Azithromycin is the preferred first-line antibiotic when indicated:

For acute watery diarrhoea (when criteria met):

• Azithromycin 500 mg single oral dose 2, 4

For febrile dysentery (bloody stools with fever ≥38.5°C):

• Azithromycin 1,000 mg (1 gram) single oral dose 2, 4

Alternative fluoroquinolone regimens (second-line):

• Ciprofloxacin 750 mg single dose OR 500 mg twice daily for 3 days 2, 4
• Levofloxacin 500 mg single dose OR 500 mg once daily for 3 days 2, 4

Specific Indications for Antibiotics

Use empiric antibiotics when ANY of the following are present:

• Bloody or mucoid stools with fever ≥38.5°C (suggests Shigella, Campylobacter, invasive E. coli) 1, 2
• Recent international travel with fever or signs of sepsis 2
• Immunocompromised patient with severe illness and bloody diarrhoea 1, 2
• Watery diarrhoea persisting >5 days 1, 2
• Clinical features of sepsis with suspected enteric fever 2

Critical Antibiotic Contraindication

NEVER give antibiotics when Shiga-toxin-producing E. coli (STEC) O157 is suspected or confirmed – this markedly increases the risk of hemolytic-uremic syndrome. 1, 2

Antiemetic Therapy

Ondansetron (Adjunctive Only)

For children >4 years and adults with persistent vomiting:

• Ondansetron 0.15 mg/kg (maximum 16 mg) as a single oral or IV dose 1, 3
• Give 30 minutes before attempting ORS 1
• Benefits include reduced vomiting, improved ORS tolerance, and decreased need for IV therapy 1
• Do not use routinely in children under 4 years 1

Nutritional Management

Resume a normal, age-appropriate diet immediately during or after rehydration – do not withhold food. 1, 3, 2

Recommended foods:

• Starches: rice, potatoes, noodles, crackers, bananas 1, 3
• Cereals: unsweetened rice, wheat, oats 1
• Yogurt, cooked vegetables, fresh fruits 1, 3
• Continue breastfeeding throughout illness in infants 1, 3, 2

Foods to avoid during acute phase:

• Soft drinks, undiluted fruit juice, sports drinks (excessive simple sugars, wrong electrolyte composition) 1, 3
• High-fat foods (delay gastric emptying) 1
• Caffeinated beverages (worsen motility) 3

Adjunctive Therapies

Probiotics

• May be offered to immunocompetent patients to reduce symptom severity and duration 3, 2

Zinc Supplementation (Children Only)

• 10–20 mg orally daily for 10–14 days for children 6 months to 5 years in zinc-deficient areas or with malnutrition 1, 2

Hospitalization Criteria

Admit immediately if ANY of the following are present:

• Severe dehydration (≥10% fluid deficit) with altered mental status 1, 3
• Signs of shock or sepsis 3, 2
• Failure of oral rehydration despite proper technique 1, 3
• Intractable vomiting despite ondansetron 1
• Infants <3 months (higher complication risk) 1, 3
• Bloody diarrhoea with fever and systemic toxicity (monitor for hemolytic-uremic syndrome) 1

Critical Red-Flag Signs

Seek immediate medical attention for:

• Bilious (green) vomiting – suggests intestinal obstruction 1
• Bloody stools with high fever – bacterial dysentery risk 1, 2
• Absent bowel sounds – absolute contraindication to oral rehydration 1
• Severe lethargy or altered consciousness – severe dehydration 1
• Decreased urine output (<3 wet diapers/24h in infants) – worsening dehydration 1, 3
• Prolonged skin tenting >2 seconds, cool extremities, poor capillary refill 1

Common Pitfalls to Avoid

• Never prioritize antibiotics or antimotility agents over rehydration – dehydration drives morbidity and mortality, not diarrhoea itself 2
• Never use sports drinks, apple juice, or soft drinks as primary rehydration fluids – they lack appropriate electrolyte balance 1, 3
• Never start antibiotics for bloody diarrhoea before ruling out STEC with Shiga-toxin testing 2
• Never delay IV rehydration in severe dehydration while attempting oral rehydration 2
• Never withhold food during the diarrheal episode – early refeeding shortens illness duration 1, 3, 2