What are the doses of medications used to treat acute gastroenteritis?

Medication Dosing in Acute Gastroenteritis

Oral rehydration solution (ORS) is the primary treatment for acute gastroenteritis, with specific medication dosing reserved for symptom management and select clinical scenarios. 1

Oral Rehydration Solution Dosing

For mild to moderate dehydration, administer ORS 50-100 mL/kg over 3-4 hours in infants and children, or 2-4 L in adolescents and adults. 1

Maintenance and Ongoing Loss Replacement

• Children <10 kg: 60-120 mL ORS after each diarrheal stool or vomiting episode (maximum ~500 mL/day) 1
• Children >10 kg: 120-240 mL ORS after each diarrheal stool or vomiting episode (maximum ~1 L/day) 1
• Adolescents and adults: Ad libitum ORS, up to ~2 L/day 1

Severe Dehydration

Administer intravenous isotonic crystalloid (lactated Ringer's or normal saline) boluses of 20 mL/kg until pulse, perfusion, and mental status normalize. 1 Malnourished infants may benefit from smaller 10 mL/kg boluses due to reduced cardiac reserve. 1

Loperamide (Antidiarrheal)

Loperamide is contraindicated in children <18 years with acute diarrhea. 2, 3

Adult Dosing

• Initial dose: 4 mg orally 1, 4
• Maintenance: 2 mg after each unformed stool or every 4 hours 1
• Maximum daily dose: 16 mg/day 1, 4

Important caveat: Loperamide should only be given to immunocompetent adults with acute watery diarrhea once adequately hydrated, and must be avoided in inflammatory diarrhea, bloody diarrhea, or fever. 3

Ondansetron (Antiemetic)

Ondansetron may be given to children >4 years and adolescents to facilitate oral rehydration when vomiting is significant. 2

• Pediatric dosing (weight-based):
  • 8-15 kg: 2 mg orally
  • 15-30 kg: 4 mg orally

  • 30 kg: 8 mg orally 5, 6

• Single-dose administration is effective in reducing hospital admissions and need for IV rehydration 7, 6

The evidence shows ondansetron decreases vomiting rates, improves oral intake success, and reduces ED length of stay with minimal side effects. 6, 8

Octreotide (For Complicated Diarrhea)

In complicated or severe diarrhea (particularly chemotherapy-induced), octreotide starting dose is 100-150 mcg subcutaneously three times daily. 1

• Alternative IV dosing: 25-50 mcg/hour continuous infusion 1
• Dose escalation: Up to 500 mcg subcutaneously three times daily until diarrhea is controlled 1

This applies primarily to cancer patients with complicated chemotherapy-related diarrhea requiring hospitalization. 1

Probiotics

Probiotics may reduce symptom severity and duration in both adults and children, though specific dosing varies by strain. 2, 3 Current evidence is insufficient to support routine use in outpatient pediatric gastroenteritis in developed countries, despite their growing popularity. 7

Zinc Supplementation

Zinc supplementation reduces diarrhea duration in children 6 months to 5 years in areas with high zinc deficiency or malnutrition. 2, 3 Standard dosing is 10-20 mg daily for 10-14 days, though this is primarily relevant in developing countries.

Antibiotics (Select Cases Only)

Empiric antibiotics are NOT routinely recommended for acute gastroenteritis. 2, 3 When indicated for specific bacterial pathogens:

• Fluoroquinolones (adults): Ciprofloxacin 500 mg twice daily for 3-5 days 3
• Azithromycin (children and adults): 10 mg/kg day 1, then 5 mg/kg days 2-5 (pediatric); 500 mg day 1, then 250 mg days 2-5 (adult) 3
• Third-generation cephalosporins (children): Ceftriaxone 50-100 mg/kg/day 3

Critical Pitfalls to Avoid

• Never delay rehydration while awaiting diagnostic testing 2, 3
• Never use antimotility agents in children <18 years or in bloody diarrhea/fever 2, 3
• Never use sports drinks or apple juice as primary rehydration for moderate-severe dehydration 1, 2
• Never give antibiotics for STEC O157 infections (increases hemolytic uremic syndrome risk) 3
• Never exceed loperamide maximum daily dose of 16 mg due to cardiac adverse reaction risk 4