• treat nausea and vomiting
  • act by inhibiting dopamine or serotonin receptors in the brain
  • act to block various pathways preventing signals from reaching the VC or CTZ


Physiologic vomiting triggers

  1. Stimulus of the vomiting center – VC
  2. Stimulus of the chemoreceptor trigger zone – CTZ


Secondary to nausea and vomiting is dehydration

  • excessive fluid loss can lead to acid-base disturbances


Types of antiemetics

  1. anticholinergics
  2. Antihistamines
  3. Benzodiazepines
  4. Cannabinoids
  5. Glucocorticoids
  6. Phenothiazines
  7. Serotonin Receptor Antagonists


Acholinergics (Scopalamine)

  • block Ach receptors in the vestibular nuclei and reticular formation
  • prevent stimuli from these areas being transmitted to VC or Chemoreceptor trigger zone


Antihistamines (Gravol or dimenhydrinate)

  • bind histamine receptors inhibiting the binding of Ach to vestibular nuclei and reticular formation


Neuroleptic agents (Phenothiazines)

  • block dopamine receptors in the chemoreceptor trigger zone
  • meds also relieve vertilago
  • use in chemo tx of nausea and vomiting


Prokinetic agents (Maxeran)

  • blocks dopamine in the CTZ and stimulates GI peristalsis
  • acts to tighten gastroesophageal sphincter preventing GERD
  • aids in gastric emptying – used for tube feed pts
  • Maxeran must be reduced if diarrhea develops
  • SE – drowsiness


Serotonin blockers (Odancetron aka Zofran)

  • blocks serotonin receptors in the GI, VC and CTZ
  • often effective when gravol is not

Benzodiazepines (Ativan)

  • decreases response in VC and CTZ
  • used as a adjunct to treat nausea and vomiting, not alone
  • uncommon in the tx of nausea and vomiting



  • action in N and V tx unclear
  • used in adjunct with other antiemetics
  • used in chemo related N and V
  • not a first line antiemetic due to it being a steroid, decreasing immunity and elevating the WBC count


Antiemetic considerations:

  • liver and kidney Fx
  • Fluid and electrolyte balance (dehydration risk)
  • BP & P – hypovolemia risk


Antiemetic choice considerations

  1. if vomiting occurs after a meal, administer prior to meal
  2. If gravol is ineffective use Serotonin blockers (Odancetron)

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