Professional drug monograph | Last reviewed: 21 September 2026
Indications and clinical role
Ondansetron is a 5-HT3 antagonist used to prevent nausea and vomiting associated with emetogenic chemotherapy and surgery. It treats emesis risk; it does not correct the underlying cause of unexplained vomiting.
Strengths and marketed formulations
- Injection commonly contains 2 mg/mL; the India-market example shown is 4 mg/2 mL in 2 mL ampoules.
- Other oral and injectable strengths exist; preparation instructions below apply only after confirming the actual product.
Adults and verified paediatric dosing
| Setting | Verified label-based regimen |
|---|---|
| Adult emetogenic chemotherapy | 0.15 mg/kg IV per dose (maximum 16 mg per dose), three doses: first over 15 min starting 30 min before chemotherapy, then at 4 and 8 h. |
| Paediatric chemotherapy, 6 months–18 years | 0.15 mg/kg IV per dose (maximum 16 mg), three doses at the same times; dilute each dose in 50 mL compatible fluid and infuse over 15 min. |
| Adult postoperative nausea/vomiting | 4 mg IV or IM as a single dose around induction or postoperatively, according to the product label and protocol. |
| Paediatric postoperative, 1 month–12 years | ≤40 kg: 0.1 mg/kg IV; >40 kg: 4 mg IV, administered per label around induction or postoperatively. |
Educational calculation example
A 24 kg child prescribed 0.15 mg/kg needs 24 × 0.15 = 3.6 mg. With 2 mg/mL solution, withdraw 3.6 ÷ 2 = 1.8 mL, then prepare and infuse according to the indication-specific label/protocol.
Reconstitution, dilution and preparation
The injection is a solution and normally needs no reconstitution. Chemotherapy doses should be diluted in 50 mL of a compatible infusion fluid as specified by the current label. Postoperative 4 mg dosing may be administered undiluted by the approved IV/IM method. Inspect solution and use aseptic technique.
Route, administration method and rate
IV or IM depending on indication and label. Chemotherapy doses are infused over 15 minutes. Avoid rapid IV administration outside the product’s approved instructions; monitor high-risk patients.
Storage, stability and compatibility
Protect and store exactly as the marketed pack directs. Stability after dilution depends on container, diluent, concentration and aseptic conditions; follow the actual label and pharmacy protocol. Do not assume compatibility with the same line as other medicines.
Renal and hepatic considerations
No routine renal dose adjustment is generally required by the referenced label. In severe hepatic impairment, total daily dose should not exceed 8 mg. Confirm the applicable label because hepatic recommendations may be formulation-specific.
Pregnancy and lactation
Use after individualized benefit–risk assessment. Human pregnancy data do not remove the need to consider indication, gestation and alternatives. Lactation decisions should consider available label data, infant factors and clinical need.
Contraindications and major interactions
- Hypersensitivity to ondansetron or product components.
- Concomitant apomorphine is contraindicated because profound hypotension and loss of consciousness have been reported.
- Additive QT risk with QT-prolonging medicines or electrolyte abnormalities.
- Serotonin syndrome has been reported with serotonergic drugs; monitor clinically.
Monitoring
Clinical response, hydration and underlying cause; ECG and electrolytes in patients with congenital long-QT syndrome, heart failure, bradyarrhythmia, electrolyte disturbance or other QT-prolonging drugs; liver function when clinically indicated.
Adverse effects
Common: headache, constipation, injection-site reactions and transient liver-enzyme changes. Serious: QT prolongation/torsades, hypersensitivity/anaphylaxis, serotonin syndrome and clinically significant hypotension.
India availability caveat
Multiple generic brands and presentations are marketed. The pictured Ondanwell pack is a representative manufacturer example; it is not a recommendation, endorsement or guarantee of current local availability.
What is known, and what is uncertain
Known: label-based indication-specific doses, concentration and major warnings summarized above. Uncertain: off-label regimens, local compatibility data and current brand supply must be verified locally.
Official and product sources
- FDA prescribing information — Zofran (ondansetron) injection
- Wellona Pharma — Ondanwell 4 mg/2 mL product page and image
Related reading
Drug Doses & Preparation A–Z · Atropine injection guide