What are the treatment options for acute and chronic diarrhea in adult patients?

Types and Treatment of Diarrhea in Adults

Classification of Diarrhea

Diarrhea is classified by duration: acute (<14 days), persistent (14-30 days), and chronic (>30 days), with acute diarrhea primarily caused by infectious organisms (viruses most common, followed by bacteria and parasites) and chronic diarrhea having diverse etiologies requiring identification of underlying causes. 1, 2

Acute Diarrhea Subtypes

• Watery (non-inflammatory): Typically viral or toxin-mediated, without fever or blood 3
• Inflammatory/dysentery: Defined as fever >38.5°C AND/OR frank blood in stools, suggesting invasive bacterial pathogens 4, 5

Chronic Diarrhea

• Requires evaluation for underlying causes including inflammatory bowel disease, malabsorption, medications, or functional disorders 2
• Most patients have self-limiting symptoms or functional gastrointestinal disorders 2

Initial Assessment and Triage

Immediately determine if warning signs are present that require urgent medical supervision rather than self-treatment. 3

Criteria for Safe Self-Medication

Self-treatment is appropriate ONLY when ALL of the following are met:

• Age >12 years (some guidelines accept >6 years) 4
• Previously healthy without significant systemic illness 4, 3
• NOT frail elderly (>75 years) 4, 5
• Absence of warning signs (see below) 4, 3

Warning Signs Requiring Medical Supervision

Seek immediate medical attention if ANY of the following are present:

• High fever >38.5°C AND/OR frank blood in stools (dysentery) 4, 3, 5
• Severe vomiting preventing oral intake 4, 3
• Signs of severe dehydration: altered mental status, absent peripheral pulse, hypotension, poor skin turgor 3
• Immunosuppression or immunosuppressive therapy 2
• No improvement within 48 hours or worsening symptoms 3, 5
• Abdominal distension suggesting complications 3

Treatment Algorithm for Acute Diarrhea

Step 1: Rehydration (ALWAYS First Priority)

Fluid replacement is the cornerstone of treatment and must be addressed before any pharmacological intervention. 5

For Mild-Moderate Dehydration (Most Cases)

• Oral rehydration is preferred: Maintain adequate fluid intake guided by thirst 3
• Glucose-containing drinks (lemonades, sweet sodas, fruit juices) or electrolyte-rich soups are sufficient for otherwise healthy adults 4, 3
• Formal oral rehydration solutions (ORS) are NOT needed in healthy adults as they do not reduce stool volume or duration, only prevent dehydration 3

For Severe Dehydration

• Intravenous isotonic fluids are required for shock, absent peripheral pulse, hypotension, or altered mental status 3

Step 2: Dietary Management

Continue eating solid food guided by appetite—there is NO evidence that fasting benefits adults with acute diarrhea. 4, 3

• Resume age-appropriate usual diet during or immediately after rehydration 3
• Avoid fatty, heavy, spicy foods and caffeine 3
• Small, light meals may be better tolerated 3
• Consider avoiding lactose-containing foods (except yogurt and firm cheeses) in prolonged episodes 3

Step 3: Pharmacological Treatment

Antimotility Agents (First-Line for Uncomplicated Watery Diarrhea)

Loperamide is the drug of choice for acute watery diarrhea in adults, with an initial dose of 4 mg followed by 2 mg after each loose stool (maximum 16 mg/day). 3, 5, 6

Key Points:

• Loperamide acts locally in the gut with minimal systemic absorption 5
• The outdated belief that antimotility agents "trap toxins" and prolong illness is NOT evidence-based—modern evidence shows loperamide safely relieves symptoms without prolonging illness in uncomplicated cases 3
• Discontinue once stools become formed 5
• FDA-approved for acute nonspecific diarrhea in patients ≥2 years and chronic diarrhea in adults with inflammatory bowel disease 6

ABSOLUTE CONTRAINDICATIONS to loperamide:

• Age <18 years (for self-medication) 5
• Bloody diarrhea or dysentery (fever >38.5°C AND/OR blood in stools) 3, 5
• Suspected inflammatory/invasive diarrhea 3
• Suspected megacolon toxicum 5

Antiemetic Agents

• Ondansetron facilitates tolerance of oral rehydration in adults with vomiting 3

Antibiotics (Selective Use Only)

Antibiotics are NOT routinely indicated for all acute diarrhea and should be restricted to specific situations to prevent antimicrobial resistance. 4

Indications for empirical antibiotic therapy:

• Moderate-to-severe traveler's diarrhea 3
• Dysentery (fever AND/OR bloody stools) 3, 5
• Known bacterial pathogen requiring treatment 3
• Diarrhea persisting beyond 5 days 5

First-line antibiotic choices:

• Azithromycin: Preferred first-line for both acute watery diarrhea (500 mg single dose) and febrile diarrhea/dysentery (1000 mg single dose) 7
• Quinolones (ciprofloxacin, levofloxacin): Alternative for traveler's diarrhea, but increasing resistance particularly among Campylobacter 4, 7
• Combination loperamide + antibiotic can be used for moderate-severe traveler's diarrhea 5, 7

Important caveat: Empirical antimicrobial use for all acute diarrheal episodes in developed countries is NOT in the best interest of public health due to increasing bacterial resistance 4

Treatment of Chronic Diarrhea

Chronic diarrhea requires identification of the underlying cause before specific therapy can be initiated. 2

• Loperamide is FDA-approved for chronic diarrhea associated with inflammatory bowel disease 6
• Octreotide 100-150 mcg subcutaneously three times daily (can titrate to 500 mcg) for refractory cases 3
• Patients with red flag symptoms (blood in stool, weight loss, anemia, palpable abdominal mass) need urgent gastroenterology referral 2

When to Escalate Care

Stop self-medication and seek medical attention if:

• No improvement within 48 hours 3, 5
• Worsening symptoms or overall condition 3
• Development of any warning signs listed above 3, 5
• Diarrhea approaching or exceeding 5 days duration 5

Prevention Strategies

• Practice proper hand hygiene after toilet use, before eating, and after handling garbage 3
• Safe food preparation and access to clean water 3, 8
• Use infection control measures (gloves, gowns) when caring for people with diarrhea 3

Common Pitfalls to Avoid

• Do NOT withhold antimotility agents based on the outdated "trapping toxins" myth in uncomplicated watery diarrhea 3
• Do NOT use loperamide if ANY contraindications are present, particularly bloody diarrhea or high fever 3, 5
• Do NOT prescribe antibiotics empirically for all cases—reserve for specific indications to prevent resistance 4
• Do NOT recommend fasting—there is no evidence it benefits adults with acute diarrhea 4, 3
• Do NOT exceed 16 mg/day of loperamide to avoid risks such as paralytic ileus 5