What is the first line of treatment for diarrhea?

First-Line Treatment for Diarrhea

Oral rehydration solution (ORS) is the first-line treatment for diarrhea, regardless of age or underlying cause, with the primary goal being prevention and correction of dehydration. 1, 2

Immediate Rehydration Strategy

The cornerstone of diarrhea management is oral rehydration using reduced osmolarity ORS (total osmolarity <250 mmol/L) containing 50-90 mEq/L of sodium. 3, 1, 2 This approach is recommended by the Infectious Diseases Society of America, WHO, and American Academy of Pediatrics as superior to intravenous therapy for mild-to-moderate dehydration. 1

Dosing by Severity

• Mild dehydration (3-5% fluid deficit): Administer 50 mL/kg of ORS over 2-4 hours 1
• Moderate dehydration (6-9% fluid deficit): Administer 100 mL/kg of ORS over 2-4 hours 1
• Severe dehydration (≥10% fluid deficit): This is a medical emergency requiring immediate IV rehydration with 20 mL/kg boluses of Ringer's lactate or normal saline until pulse, perfusion, and mental status normalize, then transition to ORS 1, 2

Practical Administration Techniques

If vomiting is present, give small frequent volumes (5-10 mL) of ORS every 1-2 minutes, gradually increasing as tolerated. 2 This approach from the WHO prevents overwhelming the stomach and improves tolerance. For patients who cannot tolerate oral intake but have normal mental status, nasogastric administration may be considered. 2

Commercially available products meeting these specifications include Pedialyte, CeraLyte, and Enfalyte/Infalyte. 1 These are preferable to homemade solutions for consistency and safety.

Nutritional Management

Resume age-appropriate normal diet during or immediately after rehydration is complete—do not "rest the bowel" through fasting. 3, 1, 2 This recommendation from the American Academy of Pediatrics and WHO contradicts older practices of prolonged dietary restriction.

Breastfed infants must continue nursing throughout the illness without interruption. 1, 2 For bottle-fed infants, use full-strength, lactose-free, or lactose-reduced formulas immediately upon rehydration. 1

When ORS Fails: Transition to IV Therapy

Switch to intravenous rehydration if any of the following occur: 1

• Severe dehydration, shock, or altered mental status present
• Paralytic ileus develops
• Patient cannot tolerate oral or nasogastric intake
• ORS therapy fails after adequate trial

A meta-analysis of 17 RCTs involving 1,811 pediatric patients demonstrated no clinically important differences between ORS and IV therapy in rehydration success, weight gain, electrolyte abnormalities, or diarrhea duration, supporting ORS as the safer first-line approach. 1

Pharmacological Adjuncts (Secondary Considerations)

Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated, but should NOT be given to children under 18 years. 2 The FDA warns that loperamide is contraindicated in pediatric patients less than 2 years of age due to risks of respiratory depression and serious cardiac adverse reactions. 4

Antimotility drugs must be avoided in inflammatory diarrhea (bloody stools), diarrhea with fever, or when toxic megacolon is suspected. 2, 4 The FDA specifically warns to discontinue loperamide promptly when constipation, abdominal distention, or ileus develop. 4

Critical Pitfalls to Avoid

Do not use sports drinks, sodas, or juices for rehydration—these have inappropriate osmolality and electrolyte composition. 3 The CDC specifically notes that soft drinks are not recommended due to their high osmolality. 1

Do not withhold food or delay refeeding—early nutrition improves outcomes and prevents malnutrition. 1, 2 This is particularly important in developing countries where malnutrition compounds diarrheal illness. 3

Dehydration assessment must be performed through physical examination focusing on skin turgor, mucous membrane moisture, capillary refill, mental status, and perfusion—not just patient-reported symptoms. 1 Rapid deep breathing, prolonged skin retraction time, and decreased perfusion are the most reliable indicators per the CDC. 1

When to Escalate Care

Seek medical evaluation for: 2, 5

• Inability to tolerate oral fluids despite small-volume technique
• Worsening signs of dehydration
• Development of bloody diarrhea
• Significant fever
• Symptoms persisting beyond 5 days (especially in elderly patients over 75 years who require physician supervision) 5