Ondansetron
Ondansetron
Zofran, Zofran ODT
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Summary
Classes
Common uses
Chemotherapy-induced nausea and vomiting0, Postoperative nausea and vomiting0, Radiation-induced nausea and vomiting0, Acute gastroenteritis in children (off-label)0
Pharmacy
Starting dose
4-8 mg PO or IV every 8 hours as needed; 16 mg single dose preoperatively for PONV prevention
Preparations
4 mg, 8 mg, 24 mg tablets; 4 mg, 8 mg orally disintegrating tablets; 4 mg/5 mL oral solution; IV (2 mg/mL)
US FDA Max
Single doses ≤16 mg (FDA 2012 advisory withdrew the 32 mg single IV dose for QT-prolongation risk); 24-32 mg/d divided
Pharmacology
Routes
Oral, IV, IM
Onset
30 minutes PO; minutes IV
Duration
4-12 hours
Half-life
3-6 hours (longer in hepatic impairment)[1]
Bioavailability
~60% (oral)[1]
Pregnancy
Widely used for hyperemesis gravidarum; meta-analyses show a small absolute signal for orofacial clefts and possible cardiac defects but the absolute risk is low and benefit usually outweighs.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Ondansetron is a selective antagonist of the 5-HT3 (serotonin type 3) receptor on vagal afferents in the gut and on chemoreceptor trigger zone neurons in the area postrema, blocking the serotonin-driven emetogenic signaling that follows chemotherapy, abdominal surgery, and radiation.0 Dose-dependent QT-interval prolongation is the principal class safety concern, driving the FDA limit on single doses[1]. CYP3A4, CYP2D6, and CYP1A2 metabolism; ultra-rapid CYP2D6 metabolizers may have reduced efficacy, an actionable PGx consideration[2].
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Zofran (ondansetron), Novartis, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/020007s050,020403s019lbl.pdf
- ↑ CPIC Guideline for CYP2D6 and Ondansetron / Tropisetron, 2017. https://cpicpgx.org/guidelines/cpic-guideline-for-ondansetron-and-tropisetron-and-cyp2d6/