Ondansetron

Ondansetron is a selective 5-HT 3 receptor antagonist. While its mechanism of action has not been fully characterized, ondansetron is not a dopamine-receptor antagonist.

• Ondansetron tablets are indicated for the prevention of nausea and vomiting associated with: highly emetogenic cancer chemotherapy, including cisplatin greater than or equal to 50 mg/m 2 . initial and repeat courses of moderately emetogenic cancer chemotherapy.ICD-10: R11.2

• Ondansetron is contraindicated in patients: known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any of the components of the formulation [see Adverse Reactions (6.2) ] receiving concomitant apomorphine due to the risk of profound hypotension and loss of consciousness Patients known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any components of the formulation.contraindicated

See full prescribing information for the recommended dosage in adults and pediatrics (2) Patients with severe hepatic impairment: do not exceed a total daily dose of 8 mg ( 2.2 , 8.6 ) 2.1 Dosage The recommended dosage regimens for adult and pediatric patients are described in Table 1 and Table 2, respectively. Corresponding doses of ondansetron tablets may be used interchangeably. Table 1: Adult Recommended Dosage Regimen for Prevention of Nausea and Vomiting Indication Dosage Regimen Highly Emetogenic Cancer Chemotherapy A single 24 mg dose administered 30 minutes before the start of single-day highly emetogenic chemotherapy, including cisplatin greater than or equal to 50 mg/m 2 Moderately Emetogenic Cancer Chemotherapy 8 mg administered 30 minutes before the start of chemotherapy, with a subsequent 8 mg dose 8 hours after the first dose. Then administer 8 mg twice a day (every 12 hours) for 1 to 2 days after completion of chemotherapy. Radiotherapy For total body irradiation : 8 mg administered 1 to 2 hours before each fraction of radiotherapy each day. For single high-dose fraction radiotherapy to the abdomen : 8 mg administered 1 to 2 hours before radiotherapy, with subsequent 8 mg doses every 8 hours after the first dose for 1 to 2 days after completion of radiotherapy. For daily fractionated radiotherapy to the abdomen : 8 mg administered 1 to 2 hours before radiotherapy, with subsequent 8 mg doses every 8 hours after the first dose for each day radiotherapy is given. Postoperative 16 mg administered 1 hour before induction of anesthesia.

Hypersensitivity Reactions, Including Anaphylaxis and Bronchospasm : Discontinue ondansetron if suspected. Monitor and treat promptly per standard of care until signs and symptoms resolve ( 5.1 ) QT Interval Prolongation and Torsade de Pointes : Avoid ondansetron tablets in patients with congenital long QT syndrome; monitor with electrocardiograms (ECGs) if concomitant electrolyte abnormalities, cardiac failure or arrhythmias, or use of other QT prolonging drugs. ( 5.2 ) Serotonin Syndrome : Reported with 5-HT 3 receptor antagonists alone but particularly with concomitant use of serotonergic drugs. If such symptoms occur, discontinue ondansetron and initiate supportive treatment. If concomitant use of ondansetron with other serotonergic drugs is clinically warranted, patients should be made aware of a potential increased risk for serotonin syndrome. ( 5.3 ) Myocardial Ischemia: Monitor or advise patients for signs and symptoms of myocardial ischemia after oral administration. (5.4) Masking of Progressive Ileus and/or Gastric Distension Following Abdominal Surgery or Chemotherapy-Induced Nausea and Vomiting : Monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction. (5.5) 5.1 Hypersensitivity Reactions Hypersensitivity reactions, including anaphylaxis and bronchospasm, have been reported in patients who have exhibited hypersensitivity to other selective 5-HT 3 receptor antagonists.

The following clinically significant adverse reactions are described elsewhere in the labeling: Hypersensitivity Reactions [see Warnings and Precautions ( 5.1 )] QT Prolongation [see Warnings and Precautions (5.2 )] Serotonin Syndrome [see Warnings and Precautions ( 5.3 )] Myocardial Ischemia [see Warnings and Precautions ( 5.4 )] Masking of Progressive Ileus and Gastric Distension [see Warnings and Precautions [see Warnings and Precautions ( 5.5 )] The most common adverse reactions in adults for the: prevention of chemotherapy-induced (≥5%) are: headache, malaise/fatigue, constipation, diarrhea ( 6.1 ) prevention of radiation-induced nausea and vomiting (≥2%) are: headache, constipation, and diarrhea ( 6.1 ) prevention of postoperative nausea and vomiting (≥9%) are: headache and hypoxia ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Dr. Reddy's Laboratories Inc., at 1-888-375-3784 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice. The following adverse reactions have been reported in clinical trials of patients treated with ondansetron, the active ingredient of ondansetron. A causal relationship to therapy with ondansetron was unclear in many cases.

8.1 Pregnancy Risk Summary Published epidemiological studies on the association between ondansetron use and major birth defects have reported inconsistent findings and have important methodological limitations that preclude conclusions about the safety of ondansetron use in pregnancy ( see Data ). Available postmarketing data have not identified a drug-associated risk of miscarriage or adverse maternal outcomes. Reproductive studies in rats and rabbits did not show evidence of harm to the fetus when ondansetron was administered during organogenesis at approximately 6 and 24 times the maximum recommended human oral dose of 24 mg/day, based on body surface area (BSA), respectively ( see Data ). The background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, miscarriages, or other adverse outcomes. In the US general population, the estimated background risk of major birth defects and miscarriages in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Metabolism

Absorption Ondansetron is absorbed from the gastrointestinal tract and undergoes some first-pass metabolism. Mean bioavailability in healthy subjects, following administration of a single 8 mg tablet, is approximately 56%.

There is no specific antidote for ondansetron overdose. Patients should be managed with appropriate supportive therapy. In addition to the adverse reactions listed above, the following adverse reactions have been described in the setting of ondansetron overdose: “Sudden blindness” (amaurosis) of 2 to 3 minutes’ duration plus severe constipation occurred in one patient that was administered 72 mg of ondansetron intravenously as a single dose. Hypotension (and faintness) occurred in a patient that took 48 mg of ondansetron tablets. Following infusion of 32 mg over only a 4-minute period, a vasovagal episode with transient second-degree heart block was observed. In all instances, the adverse reactions resolved completely. Pediatric cases consistent with serotonin syndrome have been reported after inadvertent oral overdoses of ondansetron (exceeding estimated ingestion of 5 mg per kg) in young children. Reported symptoms included somnolence, agitation, tachycardia, tachypnea, hypertension, flushing, mydriasis, diaphoresis, myoclonic movements, horizontal nystagmus, hyperreflexia, and seizure.

• Dec 26, 2006ANDAANDA076960Hikma
• Dec 26, 2006ANDAANDA076183Dr Reddys Labs Ltd
• Dec 26, 2006ANDAANDA076974Fresenius Kabi Usa
• Dec 26, 2006ANDAANDA076972Fresenius Kabi Usa
• Dec 26, 2006ANDAANDA076780Hikma Farmaceutica
• Dec 26, 2006ANDAANDA076781Hikma Farmaceutica
• Dec 26, 2006ANDAANDA077365Hikma
• Dec 26, 2006ANDAANDA077406Chartwell Molecules

1. 1Nausea13,93912%
2. 2Fatigue9,8498.3%
3. 3Diarrhoea9,1907.8%
4. 4Vomiting8,5437.2%
5. 5Off Label Use7,7266.5%
6. 6Dyspnoea5,7754.9%
7. 7Pyrexia5,4974.6%
8. 8Death5,4834.6%
9. 9Headache5,4234.6%
10. 10Pain5,3534.5%
11. 11Febrile Neutropenia4,7604.0%
12. 12Constipation4,5923.9%
13. 13Asthenia4,4213.7%
14. 14Drug Ineffective4,4053.7%
15. 15Pneumonia4,0673.4%

Recent PubMed references pinned to Ondansetron as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• "Ondansetron augmentation for obsessive-compulsive disorder: A systematic review and meta-analysis of randomized placebo-controlled trials".
  European journal of clinical pharmacology · 2026 · Mohammad A, Ibrahim M, Khan AM, et al.
  PMID 42178423DOI 10.1007/s00228-026-04085-9
• Guideline-Aligned Machine Learning for Predicting Ondansetron Administration at the End of Anaesthesia: Explainable Decision Support for PONV Prophylaxis.
  Studies in health technology and informatics · 2026 · Strube T, Weltermann L, Weber J, et al.
  PMID 42174910DOI 10.3233/SHTI260235
• Ondansetron-loaded magnetically targeted nanocarriers for anxiety: optimization, in vitro characterization, and in vivo evaluation in rats.
  European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V · 2026 · Tantawy N, Elsalhy S, Alsofany JM, et al.
  PMID 41956222DOI 10.1016/j.ejpb.2026.115071
• Effect of ondansetron on QTc interval prolongation in healthy pediatric patients: a systematic review and meta-analysis.
  Revista paulista de pediatria : orgao oficial da Sociedade de Pediatria de Sao Paulo · 2026 · Carneiro IMC, Castelo Branco PES, Franco AHS, et al.
  PMID 41880414DOI 10.1590/1984-0462/2026/44/2025134
• Fosaprepitant versus Ondansetron for Preventing Postoperative Nausea and Vomiting After Video-Assisted Thoracoscopic Lung Resection: A Randomized Controlled Clinical Trial.
  Drug design, development and therapy · 2026 · Qi X, Zhang J, Sun J, et al.
  PMID 41836527DOI 10.2147/DDDT.S584402
• Impact of CYP2D6 Metabolizer Status on Ondansetron Efficacy in Early Pregnancy Induced Nausea and Vomiting: A Case Control Study.
  Clinical and translational science · 2026 · Liu M, Shuey MM, Holley SE, et al.
  PMID 41820792DOI 10.1111/cts.70523
• Impact of excipient composition and environmental humidity on the physicochemical properties of ondansetron orally disintegrating tablets: experimental and molecular simulation study.
  Journal of molecular modeling · 2026 · Aldabet A
  PMID 41806002DOI 10.1007/s00894-026-06679-7
• Ondansetron Prevents Nausea and Vomiting After Orthognathic Surgery.
  Anesthesia progress · 2026 · Fujioka E, Hanamoto H, Kozu F, et al.
  PMID 41791720DOI 10.2344/24-0055

The 10 most recently updated of 647 ClinicalTrials.gov registrations naming Ondansetron as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• Comparison of Cumulative Opioid Consumption Between Variable-Rate Feedback Infusion and Fixed-Rate Basal Infusion Modes of Intravenous PCA Following Mixed Surgery
  Recruiting · Interventional · 1,170 enrolled · Beijing Tiantan Hospital
  NCT07361822updated 2026-06-12
• Time to First Rescue Antiemetic With Ondansetron Plus Metoclopramide Versus Dexamethasone Plus Metoclopramide for PONV Prophylaxis in Laparoscopic Cholecystectomy
  Not yet recruiting · Phase 4 · Interventional · 264 enrolled · Faisalabad Medical University
  NCT07638527updated 2026-06-11
• Feasibility and Safety of a Pediatric ERAS Protocol for Laparoscopic Appendectomy
  Not yet recruiting · Interventional · 100 enrolled · Ahmet Burak Doğan, MD
  NCT07643285updated 2026-06-11
• Aprepitant to Improve Same Day Discharge for TKA
  Not yet recruiting · Phase 4 · Interventional · 350 enrolled · Endeavor Health
  NCT07639723updated 2026-06-10
• Ondansetron Versus Lidocaine for Preventing Pain on Propofol Injection.
  Not yet recruiting · Interventional · 156 enrolled · Mongi Slim Hospital
  NCT07632144updated 2026-06-08
• Multi-center RCT of IV Ketamine Efficacy and Safety in Chronic Daily Headaches
  Recruiting · Phase 3 · Interventional · 56 enrolled · University Health Network, Toronto
  NCT05306899updated 2026-06-08
• Continuous Infusion of First-Generation 5-HT3 Receptor Antagonists in Combination With Dexamethasone
  Completed · Phase 3 · Interventional · 28 enrolled · Immune Oncology Research Institute
  NCT05872893updated 2026-06-08
• Administration of TAA-Specific CTLs; Hodgkin or Non-Hodgkin Lymphoma; TACTAL
  Active not recruiting · Phase 1 · Interventional · 36 enrolled · Baylor College of Medicine
  NCT01333046updated 2026-06-03
• Study With IV NEPA (Fosnetupitant/Palonosetron) for the Prevention of Chemotherapy-induced Nausea and Vomiting in Paediatric Cancer Patients Undergoing Highly Emetogenic Chemotherapy (HEC)
  Recruiting · Phase 2 · Interventional · 95 enrolled · Helsinn Healthcare SA
  NCT06904235updated 2026-06-01
• Recommendations of Enhanced Recovery Interventions for Patient's Clinical Team and Collection of Associated Data
  Completed · Phase 3 · Interventional · 3,395 enrolled · Jennifer Holder-Murray
  NCT04606264updated 2026-05-28

CPIC-curated drug–gene pairs for Ondansetron. Levels describe the strength of curated evidence and guideline status — never a recommendation to test or to adjust therapy.

• ABCB1CPIC C/D (provisional)ClinPGx 3
• CYP2D6CPIC AClinPGx 1AFDA label: No Clinical PGx
  CYP2D6 and Ondansetron and Tropisetron

Frequently asked questions

How does Ondansetron work?

Ondansetron is a selective 5-HT 3 receptor antagonist. While its mechanism of action has not been fully characterized, ondansetron is not a dopamine-receptor antagonist.

What is Ondansetron used for?

According to FDA labeling, Ondansetron carries indications including: Ondansetron tablets are indicated for the prevention of nausea and vomiting associated with: highly emetogenic cancer chemotherapy, including cisplatin greater than or equal to 50 mg/m 2 . initial and repeat courses of moderately emetogenic cancer chemotherapy.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Ondansetron?

Ondansetron is classified as Serotonin (5HT3) antagonists, Serotonin-3 Receptor Antagonist, Serotonin 3 Receptor Antagonists, Serotonin 5HT-3 Antagonists, Decreased Central Nervous System Serotonin Activity, Decreased Peripheral Nervous System Serotonin Activity, Emesis Suppression.

What are the contraindications for Ondansetron?

Ondansetron labeling lists contraindications including: Ondansetron is contraindicated in patients: known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any of the components of the formulation [see Adverse Reactions (6.2) ] receiving concomitant apomorphine due to the risk of profound hypotension and loss of consciousness Patients known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any components of the formulation.. Always consult the full prescribing information and a clinician.