antidiarrhoeal

An antidiarrhoeal slows down an overactive gut. In diarrhoea, contents race through the bowel too fast and too watery; these drugs put a brake on movement or pull water back, so stools become firmer and less frequent.

The mainstay is loperamide, an opioid that acts on opioid receptors in the gut wall but is largely kept out of the brain, so it reduces intestinal motility and increases water absorption without causing the central effects or addiction of pain-relieving opioids. Other approaches include adsorbents and, for specific secretory or infective causes, targeted agents. The cornerstone of treatment, especially in children, remains oral rehydration to replace lost fluid and salts.

Slowing the gut is unhelpful — sometimes harmful — when diarrhoea is the body clearing an infection: in dysentery with blood and fever, or in suspected toxin-driven colitis, motility-slowing drugs can worsen outcomes and are best avoided. Antidiarrhoeals treat the symptom, not the cause, so persistent, bloody or feverish diarrhoea needs proper evaluation.