Treatment for Acute Diarrhea in Adults
Oral rehydration solution (ORS) is the first-line treatment for acute diarrhea in adults with mild to moderate dehydration, while most cases require only supportive care without antibiotics. 1
Rehydration Strategy
Oral rehydration is the cornerstone of management and should be initiated immediately for any signs of dehydration. 1
Low-osmolarity ORS (osmolarity <250 mmol/L) is the preferred formulation for all causes of diarrhea and can be safely used in both hypernatremia and hyponatremia (unless edema is present). 1
Commercially available ORS products include Pedialyte, CeraLyte, and Enfalac Lytren—avoid apple juice, Gatorade, and soft drinks as these are inappropriate for rehydration. 1
Intravenous fluids (lactated Ringer's or normal saline) should be reserved for severe dehydration, shock, altered mental status, ORS failure, or ileus. 1
Once rehydrated with IV fluids, transition to ORS for remaining deficit replacement and maintenance. 1
Continue ORS to replace ongoing stool losses until diarrhea resolves. 1
Dietary Management
Resume a normal, age-appropriate diet immediately after rehydration is complete or during the rehydration process. 1
Early refeeding is preferred and does not worsen outcomes. 2, 3
No need for dietary restrictions or bland diets in most cases. 1
Antimotility Agents
Loperamide can be used for symptomatic relief in acute watery diarrhea but must be avoided in bloody or inflammatory diarrhea. 2, 3
Loperamide/simethicone combination may improve symptoms in watery diarrhea. 3
Never use antimotility agents if blood or mucus is present in stool, as this may worsen outcomes in inflammatory/invasive diarrhea. 2, 3
Antibiotic Therapy
Empiric antibiotics are rarely warranted and should be avoided in most cases of acute watery diarrhea. 2, 4
When to Consider Antibiotics:
- Severe illness with signs of sepsis 2, 4
- Bloody diarrhea (dysentery) with inflammatory features 4, 3
- Immunocompromised patients 4, 3
- Travelers' diarrhea with moderate to severe symptoms 4, 3
- Patients >65 years with severe symptoms 4
- Suspected or confirmed specific pathogens: Shigella, Campylobacter, C. difficile, or protozoal infections 4, 3
Targeted Antibiotic Use:
Antibiotics should ideally be guided by stool microbiologic assessment rather than given empirically. 2
When used appropriately, antibiotics are effective against shigellosis, campylobacteriosis, C. difficile colitis, traveler's diarrhea, and protozoal infections. 4, 3
Diagnostic Testing
Most episodes of acute diarrhea do not require laboratory workup or stool studies. 2, 3
Reserve Testing For:
- Severe dehydration or sepsis 2, 3
- Persistent fever 2, 3
- Bloody or mucoid stools 2, 3
- Immunocompromised patients 2, 3
- Recent hospitalization or suspected nosocomial infection 2, 3
- Suspected outbreak 2, 3
Preferred Diagnostic Approach:
Molecular studies (PCR) are preferred over traditional stool cultures unless an outbreak is suspected. 2
Consider complete blood count, creatinine, electrolytes, stool leukocytes/lactoferrin, C. difficile testing, and ova/parasites examination when indicated. 4
Probiotics
Probiotics may shorten the duration of illness but are not routinely necessary for most adults. 3
- Evidence is stronger in pediatric populations than adults. 3
Common Pitfalls to Avoid
Do not use sports drinks or fruit juices for rehydration—they lack appropriate electrolyte composition and have excessive osmolarity. 1
Do not routinely prescribe antibiotics for watery diarrhea—most cases are viral and self-limited, and inappropriate antibiotic use contributes to resistance. 2, 4
Do not give antimotility agents with bloody diarrhea—this can prolong pathogen clearance and worsen invasive infections. 2, 3
Do not delay IV rehydration in severe dehydration—oral rehydration fails in approximately 4% of cases requiring escalation. 1