Loperamide

Mechanism of Action:
Peripherally acting ยต opioid receptor agonist which is negligibly absorbed from gut and does not cross blood-brain barrier. It therefore acts on opioid receptors in the myenteric plexus of the gut, but not in the CNS.

Indications:

  • Non-infective diarrhoea
  • Reducing output of stoma

Mu opioid receptors are transmembrane G-protein coupled receptors. Activation prevents adenylate cyclase from converting ATP to cyclic AMP. This opens potassium channels (potassium leaves the cell), leading to hyperpolarisation and decreased neuronal excitability. It also blocks calcium channels which affects transmission of impulses. Hence, opioid agonists have an inhibitory effect on neurons. The activation of opioid receptors in the enteric nerve plexus enhances tone and regularity of intestinal contractions but inhibits propulsive motor activity

Lecture and CAL materials: (under review)