Ondansetron
ZOFRAN
Pronunciation: on-DAN-se-tron
“On Dancer Tron! (Go) so frantic!”
Rainbow spray → antiemetic
color coding aligned with 5-HT3 blocker peg
What it is5-HT3 receptor antagonist; nausea and vomiting.
Why this oneBroad oral, dissolving-tablet and IV availability makes it the default 5-HT3 antiemetic without sedation or motor effects.
What limits itConstipation and QT prolongation are the practical limits; avoid stacking QT-prolonging drugs. It does not treat vestibular nausea.
FDA-approved for
- nausea/vomiting (1991)
Off-label
- refractory itch
- IBS-D
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| CINV — highly emetogenic chemotherapy | Adults | 24 mg once (three 8 mg tablets) | 24 mg 30 min pre-chemo | 24 mg/dose |
| CINV — moderately emetogenic chemotherapy | Adults & children ≥12 yr | 8 mg BID | 8 mg BID | 8 mg BID |
| CINV — moderately emetogenic chemotherapy | Children 4-11 yr | 4 mg TID | 4 mg TID | 4 mg TID |
| Radiotherapy-induced N/V | Adults | 8 mg TID | 8 mg TID | 8 mg TID |
| Postoperative N/V | Adults | 16 mg once (two 8 mg tablets) 1 h before anesthesia | 16 mg once | 16 mg/dose |
Renal No adjustment needed
Hepatic Severe (Child-Pugh ≥10): do not exceed 8 mg total daily dose
Instructions
- Give first dose 30 minutes before start of chemotherapy (1-2 h before each radiotherapy fraction)
Available strengths
- tab 4, 8 mg
- ODT 4, 8 mg
Contraindications
- Concomitant use of apomorphine (profound hypotension and loss of consciousness reported)
Adverse reactions
- Headache
- Diarrhea
- Constipation
- Malaise/fatigue
- Dizziness
Pregnancy Pregnancy Category B; animal studies show no fetal harm; use only if clearly needed
Lactation Undefined
Cost
Generic entry2006
NO BOXED WARNINGS
Principal riskQT prolongation
Classes and tags
Clinical profile
Legacy pregnancy categoryB
Defining liabilitySedation, QT prolongation, extrapyramidal symptoms or anticholinergic toxicity vary by receptor target.
Serotonicity
This drug is routinely called serotonergic. By Gillman’s human-effect criteria it does not raise serotonin in the synapse.
5-HT3 antagonists block a serotonin receptor and are not Gillman-type serotonin-toxicity triggers.
Gillman’s four human testsA measurable SERT affinity that fails all four is not clinical serotonicity.
- Retarded orgasm
- Efficacy in OCD and cataplexy
- Clonus and hyperreflexia in single-drug overdose
- Serotonin toxicity when combined with an MAOI
Non-elevating action5-HT3 antagonist
Evidence confidenceHigh
Background: what serotonicity is · what is and is not an SRI · what counts as a relevant MAOI.
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