What is the recommended medication and management for an otherwise healthy adult with an acute viral gastroenteritis (stomach bug)?

Medication and Management for Acute Viral Gastroenteritis in Adults

For an otherwise healthy adult with a stomach bug, oral rehydration solution (ORS) is the primary treatment—not medication—and should be started immediately using small, frequent volumes (5-10 mL every 1-2 minutes) until rehydration is achieved. 1, 2

Primary Treatment: Oral Rehydration

• Keep commercially-available ORS packets at home as a standard item and begin administration immediately at the onset of diarrhea, before seeking medical care. 1
• Administer ORS in small, frequent volumes of 5-10 mL every 1-2 minutes via spoon, medicine cup, or syringe, gradually increasing as tolerated. 1
• The most critical error to avoid is drinking large volumes rapidly from a cup or bottle, which provokes vomiting and creates the false impression that oral rehydration has failed. 1
• Success rates exceed 90% when the small-volume, slow-administration method is used correctly. 1
• Continue ORS until clinical dehydration is corrected, then replace ongoing losses (approximately 10 mL/kg for each watery stool) until diarrhea and vomiting resolve. 1, 2

Nutritional Management

• Resume a normal age-appropriate diet immediately during or after rehydration—do not fast or restrict food. 1, 2
• Early refeeding reduces severity, duration, and nutritional consequences of diarrheal illness. 1, 2
• Avoid foods high in simple sugars (soft drinks, undiluted fruit juices), high-fat foods, and caffeinated beverages, as these can worsen diarrhea through osmotic effects and increased intestinal motility. 1

Medication Options (Limited Role)

Loperamide (Antimotility Agent)

• Loperamide may be given to immunocompetent adults with acute watery diarrhea only after adequate hydration is achieved. 1, 2
• The recommended initial dose is 4 mg (two capsules) followed by 2 mg after each unformed stool, with a maximum daily dose of 16 mg. 3
• Never use loperamide if you have bloody diarrhea, fever, or signs of inflammatory diarrhea, as serious adverse events including ileus can occur. 1, 3
• Avoid dosages higher than recommended due to risk of serious cardiac adverse reactions. 3

Bismuth Subsalicylate

• May provide symptomatic relief and has been shown to reduce illness duration modestly (from 27 to 20 hours in one study). 2

Probiotics

• Probiotic preparations may reduce symptom severity and duration in immunocompetent adults with infectious diarrhea. 1, 2

What NOT to Use

• Antimotility agents, adsorbents, antisecretory drugs, and toxin binders should not be used as they do not demonstrate effectiveness in reducing diarrhea volume or duration. 1
• Metoclopramide is explicitly contraindicated in gastroenteritis (Grade D recommendation: fair evidence that it is ineffective or harms outweigh benefits). 1
• Antimicrobial agents have limited usefulness since viral agents are the predominant cause; antibiotics should only be considered for bloody diarrhea, recent foreign travel, or immunodeficiency. 1
• Do not use sports drinks, soft drinks, or undiluted fruit juices as primary rehydration fluids—they lack appropriate electrolyte balance and contain excess simple sugars. 1

Red Flags Requiring Medical Evaluation

• Bloody diarrhea warrants immediate medical assessment for possible bacterial infection (Salmonella, Shigella, enterohemorrhagic E. coli) and consideration of antimicrobial therapy. 1
• Signs of severe dehydration: decreased urine output, dry mouth and tongue, unusual drowsiness or lethargy, rapid heartbeat. 2
• Persistent vomiting despite small-volume ORS administration indicates failure of oral rehydration therapy and may require IV fluids. 1
• Severe abdominal pain disproportionate to examination findings. 1

Infection Control

• Practice vigorous handwashing with soap for at least 10 seconds after toilet use, before food preparation and eating. 2
• Separate ill persons from well persons until at least 2 days after symptom resolution. 1, 2
• Clean and disinfect contaminated surfaces promptly. 1

Clinical Context

Viral gastroenteritis is typically self-limited and resolves within a few days. 2 The main risk is dehydration and electrolyte imbalance rather than the infection itself. 2 Lack of access to proper rehydration, rather than disease virulence, is the principal risk factor for serious complications. 2 Most adults can be managed entirely at home with ORS and do not require any medication beyond symptomatic relief if desired. 1, 2