II. Indications
- Chemotherapy associated Nausea
- Radiation Therapy associated Nausea
- Vomiting refractory to first-line Antiemetics
-
Theophylline
Overdose
- Used instead of Phenothiazines due to Seizure risk
III. Contraindications
- QTc Prolongation (see adverse effects below)
IV. Mechanism
- See 5-HT3 Receptor Antagonist
- Blocks peripheral and central 5HT3 receptors
- Peripheral 5HT3 receptors at vagal nerve terminals
- Central 5HT3 receptors at ChemoreceptorTrigger Zone in Medulla (area postrema controls Vomiting)
V. Dosing
- Dose Adjustments
- Severe Liver Disease: Max dose 8 mg orally, 16 mg IV
-
Gastroenteritis
- Adults
- Take 4 mg ODT tabs (typical acute care dosing)
- Children
- Exercise caution in age <6 months
- Weight 8-15 kg: Ondansetron 2 mg (half tab)
- Weight 15-30 kg: Ondansetron 4 mg (one tab)
- Weight >30 kg: Ondansetron 4 to 8 mg (one to two tabs)
- Freedman (2006) N Engl J Med 354:1698-705 [PubMed]
- Adults
-
Nausea with Chemotherapy
- Timing
- First dose: 30 minutes before Chemotherapy
- Subsequent dosing: 4 and 8 hours after first dose
- Thereafter, may repeat every 12 hours for 1-2 days after Chemotherapy
- Intravenous dosing
- Adult: 8 to 16 mg IV over 15 min
- Child (over age 6 months): 0.15 mg/kg up to 8 to 16 mg IV over 15 min
- Oral dosing (ODT)
- Over age 12 years: 8 mg orally twice to three times daily
- Age 4 to 11 years: 4 mg orally twice to three times daily
- Age under 4 years: 0.15 mg/kg/dose (up to 4 mg) orally twice to three times daily
- Timing
-
Nausea with Radiation Therapy (adult)
- Dose: 8 mg orally three times daily
- Surgery Related Nausea (Prevention and Treatment of Post-Operative Nausea and Vomiting)
- Adult
- Prevention: 8 to 16 mg orally 1 hour before surgery
- Treatment: 4 mg IM or IV over 2-5 minutes
- Child
- Age 1 month to 12 years (weight <40 kg): 0.1 mg/kg up to 4 mg IV over 2 to 5 min given 30 min before surgery
- Age >12 years (weight >40 kg): 4 mg IV over 2 to 5 min given 30 min before surgery
- Efficacy
- Meta-analysis of 7 randomized trials, n=1043
- Works in only 25% of patients
- No more effective than less expensive drugs
- Tramer (1997) BMJ 314:1088-93 [PubMed]
- Adult
VI. Adverse Effects
- Mild Headache
- Dizziness
- Malaise or Fatigue
- Constipation
-
QT Prolongation
- Risk Factors
- Single doses >16 mg IV
- Preexisting QTc Prolongation (avoid)
- If QTc is already prolonged, Metoclopramide (Reglan) is a safe alternative without risk of QTc Prolongation
- Congestive Heart Failure
- Bradycardia
- Hypomagnesemia
- Hypokalemia
- Unlikely to cause harm (even at highest dose, Ondansetron prolongs QTc only 20 ms)
- Risk Factors
- Serotonin Syndrome
VII. Safety
- Unknown safety in Lactation
- First trimester pregnancy
- Ondansetron has a relative contraindication based on preliminary data
- Previously thought to be safe in pregnancy
- However it is also frequently used in Hyperemesis Gravidarum
- FDA cautions use in Gestational age <10 weeks
- As of 2013, Ondansetron may be associated with 2 fold increased risk of congenital malformations
- References
- Ondansetron has a relative contraindication based on preliminary data
VIII. Drug Interactions
-
Apomorphine
- Drug Interaction with risk of hyoptension, Altered Level of Consciousness
IX. Resources
X. References
- Johnson (1993) Harriet Lane, Mosby, p. 521
- Hamilton (2020) Tarascon Pocket Pharmacopoeia
- (1998) Med Lett Drugs Ther 40(1026): 53-4 [PubMed]
- (1991) Med Lett Drugs Ther 33(847): 63-4 [PubMed]
- Bell and Lovecchio (2016) Crit Dec Emerg Med 30(8): 28
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Related Studies
| 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 |