Metoclopramide

Metoclopramide is a D2 receptor antagonist* mainly used in the management of nausea. Other uses include:

• gastro-oesophageal reflux disease
• prokinetic action is useful in gastroparesis secondary to diabetic neuropathy
• often combined with analgesics for the treatment of migraine (migraine attacks result in gastroparesis, slowing the absorption of analgesics)

Adverse effects

• extrapyramidal effects
  • acute dystonia e.g. oculogyric crisis
  • this is particularly a problem in children and young adults
• diarrhoea
• hyperprolactinaemia
• tardive dyskinesia
• parkinsonism

Metoclopramide should be avoided in bowel obstruction, but may be helpful in paralytic ileus.

• whilst metoclopramide is primarily a D2 receptor antagonist, the mechanism of action is quite complicated:
• it is also a mixed 5-HT3 receptor antagonist/5-HT4 receptor agonist
• the antiemetic action is due to its antagonist activity at D2 receptors in the chemoreceptor trigger zone. At higher doses the 5-HT3 receptor antagonist also has an effect
• the gastroprokinetic activity is mediated by D2 receptor antagonist activity and 5-HT4 receptor agonist activity