Diarrhea is classified as acute (lasting <14 days) or chronic (≥4 weeks). Key manifestations include:

• Frequent Loose Stools: ≥3 episodes/day.
• Abdominal Cramps or Pain: Often accompanied by bloating.
• Dehydration Signs: Thirst, dry mouth, reduced urination, dizziness, or lethargy.
• Fever or Blood/Mucus in Stool: Suggests infection (e.g., Salmonella, E. coli).
• Weight Loss or Malnutrition: In chronic cases (e.g., celiac disease, IBD) (Mayo Clinic).

Red Flags:

• Severe dehydration (sunken eyes, rapid heartbeat).
• High fever, persistent vomiting, or bloody stools (Lippincott Review of Pathology).

Diarrhea arises from diverse mechanisms:

1. Infectious Causes:
   • Viral: Rotavirus (common in children), norovirus.
   • Bacterial: Campylobacter, Shigella, Vibrio cholerae.
   • Parasitic: Giardia, Cryptosporidium (common in contaminated water).
2. Dietary Triggers:
   • Lactose intolerance, excessive alcohol, or artificial sweeteners.
3. Medications:
   • Antibiotics (disrupt gut flora), laxatives, PPIs, or chemotherapy.
4. Chronic Conditions:
   • Irritable bowel syndrome (IBS-D), inflammatory bowel disease (IBD), or hyperthyroidism (WHO).
5. Pathophysiological Mechanisms:
   • Osmotic: Unabsorbed substances drawing water into the gut (e.g., lactose).
   • Secretory: Excessive fluid secretion (e.g., cholera toxin) (Lippincott Textbook of Pharmacology).

Preventing diarrhea focuses on reducing exposure to pathogens and risk factors:

1. Hygiene:
   • Handwashing with soap, especially before eating.
2. Safe Food/Water:
   • Avoid raw/undercooked meats, unpasteurized dairy.
   • Use treated or boiled water in high-risk areas.
3. Vaccination:
   • Rotavirus vaccine for infants (prevents 40% of severe diarrhea cases) (WHO).
4. Probiotics:
   • Lactobacillus rhamnosus GG may reduce antibiotic-associated diarrhea (Comprehensive Pharmacy Review).

1- Rehydration:

• Oral Rehydration Solution (ORS): WHO-recommended electrolyte solution for mild-moderate dehydration.
• IV Fluids: For severe dehydration (e.g., cholera).

2. Dietary Adjustments:

• BRAT Diet: Bananas, rice, applesauce, toast (for short-term symptom relief).
• Avoid Trigger Foods: Dairy, caffeine, fatty/spicy foods during recovery.

3. Pharmacological Therapy:

• Antimotility Agents:
  • Loperamide: Reduces stool frequency (avoid in bloody diarrhea or C. difficile).
  • Bismuth Subsalicylate: Antisecretory and antimicrobial (BNF).
• Antibiotics:
  • Reserved for bacterial infections (e.g., azithromycin for travelers' diarrhea).
• Zinc Supplements: Reduce duration in children (WHO).
• Probiotics: Saccharomyces boulardii for antibiotic-associated diarrhea (Lange Textbook of Clinical Pharmacology).

4. Chronic Diarrhea Management:

• Treat Underlying Conditions: Gluten-free diet for celiac disease, anti-inflammatory drugs for IBD.
• Bile Acid Binders: Cholestyramine for bile acid malabsorption (Lippincott Textbook of Pharmacology).

5. When to Seek Care:

• Symptoms lasting >2 days (adults) or 24 hours (children).
• Signs of severe dehydration or systemic illness.

Diarrhea, though often self-limiting, requires prompt attention to prevent complications. Prevention through hygiene, safe food practices, and vaccination is key. Treatment prioritizes rehydration, with medications tailored to the cause. Chronic cases warrant medical evaluation to address underlying disorders