Dopamine receptor antagonists

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Metoclopramide

• Mechanism
  • D2 antagonist, serotonin receptor antagonist
  • Central antiemetic effect at the area postrema
  • Peripheral antiemetic effect in the gastrointestinal tract (prokinetic effect); causes increase in:
    • Gastric contractions
    • Duodenal and jejunal motility
    • Resting tone of the lower esophageal sphincter
  • Together with decreased pylorus sphincter activity allows food to pass more quickly through the stomach and the small intestine
  • No influence on colon motility
• Clinical use
  • Prokinetic effect used to treat diabetic and postsurgery gastroparesis (delayed gastric emptying)
  • Hyperemesis gravidarum
  • Persistent GERD