Antiemetics

 

  • 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

 

Glucocorticoids

  • 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)
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: