Antiemetic

Aka: Antiemetic, Anti-emetic, Phenothiazine Antiemetic, Benzamide Antiemetic, Phenothiazine

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II. Mechanism

  1. Nausea and Vomiting is mediated via the physiologic Vomiting center in the Medulla
    1. D2 Dopamine Stimulation of ChemoreceptorTrigger Zone (CTZ) in Medulla
    2. Many Antiemetics are dopamine Antagonists (e.g. Phenothiazines, Antipsychotic Medications)
    3. Serotonin Antagonists (5-HT3) are among the most commonly used Antiemetics
    4. Some Antihistamines (e.g. Diphenhydramine) and Anticholinergic Medications have Antiemetic properties (unclear mechanism)
  2. Stimulation of Vomiting center via three pathways
    1. Vestibular fibers (e.g. Vertigo)
    2. Afferent visceral fibers (e.g. gastrointestinal)
    3. Fourth Ventricle (ChemoreceptorTrigger Zone)

III. Preparations: 5-HT3 Receptor Antagonist

  1. Indications
    1. Preferred first-line Antiemetic in U.S. in most cases
    2. Severe Nausea and Vomiting
    3. Postoperative Nausea and Vomiting
    4. Chemotherapy-Induced Vomiting (See Nausea in Cancer)
  2. Agents
    1. Ondansetron (Zofran)
    2. Granisetron (Kytril)
    3. Dolasetron (Anzemet)
    4. Palonosetron (Aloxi)
  3. Adverse effects
    1. Asthenia
    2. Dizziness
    3. Constipation
    4. QT Prolongation (see Ondansetron)
    5. Serotonin Syndrome
    6. Use in pregnancy may be associated with increased risk of Congenital Heart Defect and Cleft Palate
      1. (2014) Presc Lett 21(1): 5

IV. Preparations: Dopamine Antagonists - Phenothiazines

  1. Indications
    1. Migraine Headaches
    2. Motion Sickness or Vertigo
    3. Chemotherapy-Induced (See Nausea in Cancer)
    4. Postoperative Nausea (See Nausea After Surgery)
    5. Severe Nausea and Vomiting
  2. Agents
    1. Prochlorperazine (Compazine)
    2. Promethazine (Phenergan)
  3. Adverse effects
    1. Extrapyramidal Side Effects (e.g. Dystonic Reaction)

V. Preparations: Dopamine Antagonists - Substituted Benzamides

  1. Indications
    1. Diabetic Gastroparesis
    2. Migraine Headaches
  2. Agents
    1. Metoclopramide (Reglan)
    2. Trimethobenzamide (Tigan)
  3. Adverse effects
    1. Extrapyramidal Side Effects

VI. Preparations: Dopamine Antagonists - Butyrophenones

  1. Agents
    1. Droperidol (Inapsine)
    2. Haloperidol (Haldol)
  2. Indications
    1. Chemotherapy-Induced (See Nausea in Cancer)
    2. Postoperative Nausea (See Nausea After Surgery)
  3. Adverse Effects
    1. Sedation
    2. Agitation or restlessness

VII. Preparations: Sedating Antihistamines (H1 Blockers)

  1. Agents
    1. Dimenhydrinate (Dramamine)
    2. Doxylamine (Unisom)
    3. Meclizine (Antivert)
    4. Scopolamine (Transdermal)
  2. Indications
    1. Vertigo
    2. Motion Sickness
  3. Adverse Effects (Anticholinergic effects)
    1. Sedation
    2. Constipation
    3. Dry Mouth
    4. Urinary Retention

VIII. Preparations: Neurokinin-1 Receptor Antagonist (NK1 Receptor Antagonist, Substance P Inhibitor)

  1. Agents
    1. Aprepitant (Emend, Cinvanti, Fosaprepitant)
    2. Rolapitant (Varubi)
    3. Netupitant (Akynzeo)
  2. Indications
    1. Prevention of Nausea, Vomiting with highly emetogenic Chemotherapy
      1. Typically used in combination with 5-HT3 Antagonists and Dexamethasone 20 mg daily
  3. Adverse Effects
    1. Asthenia or Fatigue
    2. Hiccups

IX. Preparations: Adjunctive and Atypical Antiemetics

  1. Dexamethasone
    1. Chemotherapy-Induced (See Nausea in Cancer)
  2. Cannabinoids (Dronabinol)
    1. Chemotherapy-Induced (See Nausea in Cancer)
  3. Benzodiazepines (Lorazepam, Diazepam, Clonazepam)
    1. Chemotherapy-Induced (See Nausea in Cancer)
    2. Not generally recommended
  4. Isopropyl Alcohol 70% Wipes
    1. Fold Alcohol wipe in half and hold within a half centimeter of the nares
    2. Take 3 deep inhalations every 5 to 15 minutes as needed (may be repeated up to 3 times)
    3. May reduce the need of medications in Postoperative Nausea and Vomiting
    4. Pellegrini (2009) AANA J 77(4): 293-9 [PubMed]
    5. Cotton (2007) AANA J 75(1): 21-6 [PubMed]

X. Preparations: Brief list of Antiemetics for Adults

  1. Ondansetron (Zofran)
    1. Dose: 4 mg (0.15mg/kg) IV (or PO) over 15 min every 4 hours as needed
  2. Metoclopramide (Reglan)
    1. Dose: 5 to 10 mg PO/IM/IV every 6 hours as needed or 1 hour before meals and at bedtime
  3. Prochlorperazine (Compazine)
    1. PO/IM/IV: 5-10 mg every 6-8 hours as needed
    2. Rectal: 25 mg PR g12h
  4. Promethazine (Phenergan)
    1. Dose: 12.5 mg IV or 25 mg PO/IM/PR every 4 to 6 hours

XI. References

  1. Flake (2015) Am Fam Physician 91(5): 293-6 [PubMed]

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