Diarrhoea

Question 1

Anti-motility drugs

Loperamide, codeine

Answer 1

• As a symptomatic treatment for diarrhoea, usually in the context of irritable bowel syndrome or viral gastroenteritis

Question 2

Anti-motility drugs

Loperamide, codeine

MOA

Answer 2

• Loperamide is an opioid that is pharmacologically similar to pethidine.
• However, unlike pethidine, is does not penetrate the central nervous system (CNS), so has no analgesic effects.
• It is an agonist of the opioid μ-receptors in the gastrointestinal tract.
• This increases non-propulsive contractions of the gut smooth muscle but reduces propulsive (peristaltic) contractions.
• As a result, transit of bowel contents is slowed and anal sphincter tone is increased.
• Slower gut transit also allows more time for water absorption, which (in the context of watery diarrhoea) has a desirable effect in hardening the stool.
• Other opioids (e.g. codeine phosphate) have similar effects but, unless analgesia is also required, there is little reason to prefer them over loperamide.

Question 3

Anti-motility drugs

Loperamide, Codeine

Important adverse

Answer 3

• In itself, loperamide is a safe drug with few adverse effects. These are mostly gastrointestinal effects predictable from its mechanism of action (e.g. constipation, abdominal cramping and flatulence).
• Indirectly, adverse effects may arise from the inappropriate inhibition of peristalsis (see Warnings).
• Where CNS-penetrating opioids are used (e.g. codeine phosphate), there is a risk of opioid toxicity and dependence

Question 4

Anti-motility drugs

Loperamide, codeine

Warnings

Answer 4

• Loperamide should be avoided in acute ulcerative colitis where inhibition of peristalsis may increase the risk of megacolon and perforation.
• For the same reason, it should be avoided where there is a possibility of Clostridium difficile colitis, including in patients who develop diarrhoea in association with broad-spectrum antibiotic use (see Clinical tip).
• It should not be used in acute bloody diarrhoea (dysentery) because this may signify bacterial infection. Particularly worrying in this context is Escherichia coli, as certain strains of this can cause a serious condition called haemolytic–uraemic syndrome (HUS). Use of antimotility drugs appears to increase the risk of HUS.

Question 5

Loperamide

Monitoring

Answer 5

• The best means of monitoring is to enquire about frequency and consistency of stools as well as abdominal pain
• NB- There are no significant interactions