II. Indications

  1. Chemotherapy associated Nausea
  2. Radiation Therapy associated Nausea
  3. Vomiting refractory to first-line Antiemetics
  4. Theophylline Overdose
    1. Used instead of Phenothiazines due to Seizure risk

III. Mechanism

  1. Blocks peripheral and central 5HT3 receptors
    1. Peripheral 5HT3 receptors at vagal nerve terminals
    2. Central 5HT3 receptors at ChemoreceptorTrigger Zone in Medulla (area postrema controls Vomiting)

IV. Contraindications

  1. First trimester pregnancy (relative contraindication based on preliminary data)
    1. Previously thought to be safe in pregnancy
    2. FDA cautions use in Gestational age <10 weeks
    3. As of 2013, Ondansetron may be associated with 2 fold increased risk of congenital malformations
      1. Congenital Heart Defects
      2. Cleft Palate
    4. References
      1. (2014) Presc Lett 21(1): 5
      2. Anderka (2012) Birth Defects Res A Clin Mol Teratol 94(1):22-30 +PMID:22102545 [PubMed]
      3. Danielsson (2014) Reprod Toxicol 50:134-7 +PMID:25450422 [PubMed]

V. Adverse Effects

  1. Mild Headache
  2. Dizziness
  3. Malaise or Fatigue
  4. Constipation
  5. QT Prolongation
    1. More common with single doses >16 mg IV
    2. If QTc is already prolonged, Metoclopramide (Reglan) is a safe alternative without risk of QTc Prolongation
    3. Unlikely to cause harm (even at highest dose, Ondansetron prolongs QTc only 20 ms)
      1. Freedman (2014) Ann Emerg Med 64(1): 19-25 +PMID:24314899 [PubMed]
      2. Moffett (2016) Acad Emerg Med 23(1): 102-5 +PMID: 26720490 [PubMed]
  6. Serotonin Syndrome
    1. http://www.fda.gov/Drugs/GuidanceComplianceRegulatoryInformation/Surveillance/AdverseDrugEffects/ucm351864.htm

VI. Dosing: Ondansetron (Zofran)

  1. Gastroenteritis using Ondansetron 4 mg ODT tabs
    1. Weight 8-15 kg: Ondansetron 2mg (half tab)
    2. Weight 15-30 kg: Ondansetron 4 mg (one tab)
    3. Weight >30 kg: Ondansetron 8 mg (two tabs)
    4. Freedman (2006) N Engl J Med 354:1698-705 [PubMed]
  2. Nausea with Chemotherapy
    1. Intravenous dosing
      1. Timing
        1. First dose: 30 minutes before Chemotherapy
        2. Subsequent dosing: 4 and 8 hours after first dose
      2. Adult: 32 mg IV over 15 min
      3. Child: 0.15 mg/kg IV over 15 min (maximum: 8 mg/dose)
    2. Oral dosing (ODT)
      1. Over age 12 years: 8 mg orally twice daily
      2. Age 4 to 11 years: 4 mg orally three times daily
      3. Age under 4 years: 0.15 mg/kg/dose (up to 4 mg)
  3. Nausea with Radiation Therapy (adult)
    1. Dose: 8 mg orally four times daily
  4. Surgery related Nausea (adult)
    1. Prevention: 8-16 mg orally 1 hour before surgery
    2. Treatment: 4 mg IV or IM over 2-5 minutes
    3. Efficacy
      1. Meta-analysis of 7 randomized trials, n=1043
      2. Works in only 25% of patients
      3. No more effective than less expensive drugs
      4. Tramer (1997) BMJ 314:1088-93 [PubMed]

VII. Dosing: Dolasetron (Anzemet)

  1. Nausea with Chemotherapy
    1. Dose: 1.8 mg/kg IV or PO for single dose to 100 mg
  2. Prevention of Surgery related Nausea
    1. Adult: 100 mg PO 2 hours before surgery
    2. Child: 1.2 mg/kg PO 2 hours before surgery
  3. Surgery related Nausea
    1. Adult: 12.5 mg IV for single dose
    2. Child: 0.35 mg/kg IV for single dose

VIII. Dosing: Granisetron (Kytril)

  1. Nausea with Chemotherapy (administer 30 minutes before)
    1. Intravenous: 10 ug/kg IV over 5 minutes
    2. Oral: 1 mg PO bid for 1 day
  2. Nausea with Radiation Therapy (adult)
    1. Dose: 2 mg PO 1 hour before each irradiation

IX. Preparations: Palonosetron (Aloxi)

  1. Indications: Preventing Chemotherapy indiuced Nausea
    1. Not effective in treating Nausea after it occurs
    2. Most effective in preventing delayed Emesis
      1. Longer Half-Life and higher 5-HT affinity
  2. Dosing: 0.25 mg IV 30 minutes before Chemotherapy
    1. Do not repeat dose more than once weekly

X. References

  1. Johnson (1993) Harriet Lane, Mosby, p. 521
  2. (2002) Tarascon Pocket Pharmacopoeia, p. 67
  3. (1998) Med Lett Drugs Ther 40(1026): 53-4 [PubMed]
  4. (1991) Med Lett Drugs Ther 33(847): 63-4 [PubMed]
  5. Bell and Lovecchio (2016) Crit Dec Emerg Med 30(8): 28

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Cost: Medications

ondansetron (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
ONDANSETRON 4 MG/5 ML SOLUTION Generic $0.25 per ml
ONDANSETRON HCL 4 MG TABLET Generic $0.07 each
ONDANSETRON HCL 4 MG/2 ML VIAL Generic $0.18 per ml
ONDANSETRON HCL 8 MG TABLET Generic $0.10 each
ONDANSETRON ODT 4 MG TABLET Generic $0.18 each
ONDANSETRON ODT 8 MG TABLET Generic $0.20 each