PH6.3 | PH6.3 | Diarrhoea Pharmacotherapy — SDL Guide — Summary & Reflection

KEY TAKEAWAYS

Diarrhoea Pharmacotherapy — Key Points:

Classification drives treatment: Secretory (watery, non-invasive) → ORS + anti-motility agents safe. Invasive/dysenteric (blood + fever) → ORS + antibiotics; anti-motility agents CONTRAINDICATED.

ORS — the most important intervention: WHO low-osmolarity formula 245 mOsm/L (glucose 75 + Na 75 + K 20 + Cl 65 + citrate 10). Mechanism: SGLT1 cotransport (intact even in cholera). Works for all secretory diarrhoeas. Never withhold. For children under 5: ORS + zinc 20 mg/day × 10–14 days (WHO).

Anti-motility agents: Loperamide (peripheral mu-opioid — safe in adults, non-invasive diarrhoea). Contraindicated: invasive/bloody/febrile diarrhoea; children under 2 years. WHO does not recommend loperamide in children. Racecadotril (enkephalinase inhibitor — antisecretory, no anti-motility, safe in paediatric acute diarrhoea).

Antibiotics: Pathogen-matched only. Ciprofloxacin for Shigella/travellers'; azithromycin for Campylobacter; metronidazole for Giardia/mild C. difficile; oral vancomycin for severe C. difficile (metronidazole inferior in severe disease). No antibiotics for viral diarrhoea or healthy adults with non-typhoidal Salmonella gastroenteritis.

C. difficile special notes: Stop precipitating antibiotic; loperamide contraindicated; oral vancomycin for severe/recurrent; fidaxomicin for recurrence reduction.

REFLECT

You are a PHC doctor seeing a mother who has brought her 18-month-old child with 3 days of watery diarrhoea. The child is alert, has some dehydration, no blood in stool, and temperature of 37.3°C. The mother asks you to prescribe 'a strong medicine — the pharmacist gave me loperamide drops last time and it worked quickly.' Think through: (a) What is the appropriate classification of this diarrhoea and does loperamide have a role? (b) What are the WHO guidelines for this specific age group and why? (c) How would you counsel the mother — acknowledging her previous positive experience with loperamide while explaining why it is not appropriate for her 18-month-old? (d) What evidence-based regimen would you prescribe? This scenario tests both pharmacological knowledge and the communication skill of explaining a prescribing refusal to a patient in a way that builds trust rather than eroding it.