Antidiarrhoeal Agents

Question 1

Opioids

Answer 1

Loperamide, Diphenoxylate Hydrochloride
Most efficacious
Inhibit Ach release through presynaptic opioid receptors in enteric nervous system
Sustained segmental contraction of SM, preventing rhythmic contraction
Choose opioids with selectivity over CNS

Question 2

Locally Acting- Absorbents

Answer 2

Kaolin-Pectin
Absorbs water and binds toxins and other irritants
Pectin decreases pH, soothing mucosa
OTC
Relief of mild to moderate diarrhoea

Question 3

Locally Acting- Antisecretory

Answer 3

Bismuth Subsalicylate
Inhibits intestinal secretion
Unknown mechanism
Useful in diarrhoea with strong secretory element