What medications are recommended for a patient with acute gastroenteritis?

Medications for Acute Gastroenteritis

The primary treatment for acute gastroenteritis is oral rehydration solution (ORS), not medications—rehydration is the cornerstone of management and should be initiated immediately. 1, 2

Rehydration as First-Line Treatment

Oral rehydration solution must be administered as the primary intervention for all patients with mild to moderate dehydration before considering any adjunctive medications. 1, 2

• Administer ORS at 50-100 mL/kg over 2-4 hours for mild to moderate dehydration (3-9% fluid deficit) 1, 2
• Use small, frequent volumes (5-10 mL every 1-2 minutes via spoon or syringe) to prevent triggering vomiting 2, 3
• Replace ongoing losses with 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 1, 2
• Low-osmolarity ORS formulations are preferred over sports drinks or juices 2

Reserve intravenous rehydration for severe dehydration (≥10% fluid deficit), shock, altered mental status, failure of oral rehydration therapy, or ileus. 1, 2 Use isotonic fluids such as lactated Ringer's or normal saline. 1

Antiemetic Medications

Ondansetron is the only antiemetic with strong evidence for use in acute gastroenteritis and should be considered when vomiting significantly impairs oral rehydration tolerance. 1, 3, 4, 5, 6

Ondansetron Dosing and Indications

• For children >4 years and adolescents: Ondansetron 0.15 mg/kg (maximum 16 mg/dose) orally, intramuscularly, or intravenously to facilitate oral rehydration when vomiting is significant 1, 3
• For adults: Ondansetron may be given after adequate hydration is achieved 1, 3
• Ondansetron reduces vomiting episodes, improves ORS tolerance, and decreases need for intravenous rehydration and hospitalization 4, 5, 6

Important Ondansetron Precautions

• Exercise special caution in children with heart disease due to potential QT interval prolongation 3
• Avoid ondansetron in patients with bloody diarrhea, fever suggesting inflammatory/bacterial diarrhea, or suspected bacterial gastroenteritis 3
• Ondansetron should only be used once the patient is adequately hydrated, not as a substitute for fluid therapy 1

Antimotility Agents: Critical Contraindications

Loperamide and other antimotility drugs should NEVER be given to children <18 years of age with acute diarrhea. 1, 2, 7

• For adults: Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated 1, 2
• Absolute contraindications at any age: Suspected or proven inflammatory diarrhea, bloody diarrhea, fever suggesting bacterial infection, or any situation where toxic megacolon may result 1, 2
• The FDA label confirms loperamide is contraindicated in pediatric patients <2 years due to risks of respiratory depression and serious cardiac adverse reactions 7

Medications NOT Recommended

Adsorbents, antisecretory drugs, and toxin binders should not be used as they do not demonstrate effectiveness in reducing diarrhea volume or duration. 2, 3

• These agents shift therapeutic focus away from appropriate fluid, electrolyte, and nutritional therapy 2
• Antimotility agents, adsorbents, antisecretory drugs, and toxin binders are explicitly not recommended by the CDC 2

Probiotics

Probiotic preparations may be offered to reduce symptom severity and duration in immunocompetent adults and children with infectious diarrhea. 1

• Evidence quality is moderate for this recommendation 1
• Specific organism selection, route, and dosage should be determined through literature searches and manufacturer guidance 1

Zinc Supplementation (Pediatric Populations)

Oral zinc supplementation reduces diarrhea duration in children 6 months to 5 years of age who reside in countries with high zinc deficiency prevalence or who have signs of malnutrition. 1, 2

• This recommendation has strong evidence in specific populations 1
• Not routinely indicated in well-nourished children in developed countries 2

Antimicrobial Therapy: Limited Role

Antimicrobial agents have limited usefulness in acute gastroenteritis management since viral agents are the predominant cause. 2

• Consider antimicrobials only for: Bloody diarrhea with fever, recent antibiotic use (test for Clostridioides difficile), exposure to certain pathogens, recent foreign travel, or immunodeficiency 2, 8
• Ciprofloxacin 500 mg orally every 12 hours for 5-7 days is appropriate for infectious diarrhea in adults when bacterial etiology is suspected 9
• Stool cultures and antimicrobial testing should guide antibiotic selection when indicated 8

Nutritional Management

Resume age-appropriate diet during or immediately after rehydration is completed—early refeeding reduces severity and duration of illness. 1, 2

• Continue breastfeeding throughout the diarrheal episode 1, 2
• Avoid foods high in simple sugars (soft drinks, undiluted apple juice) as they can exacerbate diarrhea through osmotic effects 2
• Limit or avoid caffeinated beverages as they worsen symptoms through stimulation of intestinal motility 2

Common Pitfalls to Avoid

• Never delay rehydration while awaiting diagnostic testing—initiate ORS immediately 2
• Never use inappropriate fluids (apple juice, sports drinks) as primary rehydration solutions for moderate to severe dehydration 2
• Never administer antimotility drugs to children or in cases of bloody diarrhea 1, 2, 7
• Never unnecessarily restrict diet during or after rehydration 1, 2
• Never use antiemetics as a substitute for fluid therapy—they are ancillary only 1, 3