What should I prescribe for an adult patient presenting with acute diarrhea in an urgent care setting?

Management of Acute Diarrhea in Urgent Care

For an adult presenting with acute diarrhea in urgent care, prescribe oral rehydration solution (ORS) as first-line therapy, and add loperamide 4 mg initially followed by 2 mg after each unformed stool (maximum 16 mg/day) if the patient has watery diarrhea without fever or bloody stools. 1, 2

Initial Assessment and Risk Stratification

Immediately evaluate for:

• Signs of severe dehydration (tachycardia, altered mental status, poor perfusion) requiring IV fluids 1
• Red flags for inflammatory diarrhea: fever, bloody stools, severe abdominal pain, or recent antibiotics 1, 3
• Immunocompromised status (HIV, chemotherapy, immunosuppressants) 1
• Recent travel to endemic areas or occupational food handling risks 1

Treatment Algorithm

For Mild-to-Moderate Watery Diarrhea (No Red Flags)

Rehydration is the cornerstone of management:

• Prescribe oral rehydration solution (WHO ORS or commercial preparations) to replace ongoing losses 1, 4
• ORS contains appropriate electrolytes including 20 mEq/L potassium, which is critical for replacing losses 4
• Continue ORS until clinical dehydration is corrected 1

Add symptomatic treatment:

• Loperamide 4 mg initially, then 2 mg after each unformed stool (maximum 16 mg/day) 2
• This is FDA-approved for adults and reduces stool frequency and fluid losses 2, 5
• Clinical improvement typically occurs within 48 hours 2

Dietary recommendations:

• Resume age-appropriate diet immediately after rehydration 1
• Avoid coffee, alcohol, and spicy foods 1

For Inflammatory Diarrhea (Fever, Blood, or Severe Illness)

Do NOT prescribe loperamide - antimotility agents are contraindicated due to risk of toxic megacolon 1, 2

Prescribe:

• IV isotonic fluids (lactated Ringer's or normal saline) if severe dehydration or shock present 1
• Empiric antibiotics if dysentery suspected (fluoroquinolone or azithromycin) 3
• Order stool studies: culture, ova and parasites, C. difficile if recent antibiotics 1, 3

For Moderate Dehydration Without Severe Illness

• Start with ORS - most patients can be managed without IV fluids 1
• If unable to tolerate oral intake, consider nasogastric ORS administration 1
• Reserve IV fluids for failure of ORS therapy, altered mental status, or persistent vomiting 1

Critical Contraindications and Warnings

Never prescribe loperamide when:

• Bloody diarrhea is present 1, 2
• Fever is present 1
• Patient is immunocompromised with suspected inflammatory diarrhea 1
• Patient is <18 years of age 1
• Patient has suspected toxic megacolon 1

Avoid exceeding 16 mg/day of loperamide due to serious cardiac adverse reactions including QT prolongation and Torsades de Pointes 2

Adjunctive Therapies

Consider adding:

• Probiotics to reduce symptom severity and duration in immunocompetent adults 1
• Ondansetron if significant nausea/vomiting prevents oral intake 1
• Potassium supplementation if prolonged diarrhea or signs of hypokalemia (weakness, arrhythmias) 4

When to Order Stool Studies

Diagnostic testing is indicated only when results will change management 1, 3:

• Severe dehydration requiring hospitalization 1
• Bloody diarrhea or dysentery 1
• Fever >38.5°C 1
• Immunosuppression 1
• Recent hospitalization or antibiotics (rule out C. difficile) 1
• Suspected outbreak or food handler 1
• Symptoms persisting >7 days 3

Do not order routine stool cultures in mild, self-limited watery diarrhea - this is wasteful and does not change management 3, 6

Disposition

Most patients can be discharged home with ORS and loperamide prescriptions 1, 3

Admit or refer if:

• Severe dehydration despite oral rehydration 1
• Altered mental status 1
• Hemodynamic instability 1
• Suspected surgical abdomen 7
• Inability to tolerate any oral intake 1

Common Pitfalls to Avoid

• Do not withhold loperamide in simple watery diarrhea - it is safe and effective when used appropriately 2, 5
• Do not prescribe antibiotics empirically for uncomplicated watery diarrhea - most cases are viral and self-limited 1, 3
• Do not use plain water for rehydration - ORS is formulated to optimize sodium and water absorption 1, 4
• Do not forget electrolyte replacement - potassium losses can be significant and require replacement 4