ondansetron
Brand names: Zofran
Ondansetron is a medicine that helps prevent nausea and vomiting. It is often used during cancer treatment or after surgery.
Drug Pricing (NADAC)
Generic Price
$0.31/unit
Generic Available
Yes (34 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine is used to prevent nausea and vomiting.
Common side effects
Headache, Feeling tired, Constipation
Key warnings
Ondansetron can cause heart problems like a prolonged QT interval.
How It Works
Ondansetron blocks a natural substance in your body called serotonin. Serotonin can cause nausea and vomiting. By blocking serotonin, ondansetron reduces these side effects.
How to Take It
Take ondansetron exactly as your doctor tells you. The dose depends on your treatment. For chemotherapy, you may take it 30 minutes before treatment. For surgery, you may take it 1 hour before.
Pregnancy & Breastfeeding
Talk to your doctor if you are pregnant or breastfeeding. It is not known if ondansetron will harm your unborn baby. Studies on the risk of birth defects are inconsistent.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store ondansetron tablets at room temperature (68°-77°F) in a closed container.
Side Effects (from patient reports)
Based on 64,495 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 103,354 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2003–2025.
Total Reports
103,354
Death-Related Reports
13,423
Hospitalization Reports
47,077
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | NAUSEA | 11,554 |
| 2 | FATIGUE | 8,199 |
| 3 | DIARRHOEA | 7,791 |
| 4 | VOMITING | 7,326 |
| 5 | OFF LABEL USE | 6,386 |
| 6 | DEATH | 4,872 |
| 7 | PYREXIA | 4,788 |
| 8 | DYSPNOEA | 4,707 |
| 9 | FEBRILE NEUTROPENIA | 4,495 |
| 10 | PAIN | 4,367 |
| 11 | HEADACHE | 4,223 |
| 12 | CONSTIPATION | 3,884 |
| 13 | ASTHENIA | 3,662 |
| 14 | DRUG INEFFECTIVE | 3,594 |
| 15 | PNEUMONIA | 3,446 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Ondansetron can cause heart problems like a prolonged QT interval. If you have congenital long QT syndrome, you should not take this medicine. Ondansetron can also cause Serotonin Syndrome, especially if you are taking other medicines for depression or pain. Seek immediate medical attention if you experience chest pain.
Known Drug Interactions
7.3 Tramadol Although no pharmacokinetic drug interaction between ondansetron and tramadol has been observed, data from 2 small trials indicate that when used together, ondansetron may increase patient-controlled administration of tramadol. Monitor patients to ensure adequate pain control when ondansetron is administered with tramadol.
Mechanism: Using these drugs together might make the pain reliever less effective, leading patients to need more of it to feel relief.
What to do: Watch your pain levels closely and tell your doctor if your pain medication does not seem to be working as well as it should.
In a crossover trial in 76 pediatric patients, intravenous ondansetron did not increase systemic concentrations of high-dose methotrexate.
Mechanism: These two drugs do not seem to change how much medicine stays in your system when used together.
What to do: No special changes are usually needed, but always follow your doctor's specific instructions when taking these medications.
In patients treated with potent inducers of CYP3A4 (i.e., phenytoin, carbamazepine, and rifampin), the clearance of ondansetron was significantly increased and ondansetron blood concentrations were decreased.
Mechanism: Carbamazepine makes your liver work faster to get rid of ondansetron, which lowers the amount of medicine in your body.
What to do: Your doctor may need to increase your dose of ondansetron to make sure it still works to prevent nausea.
In patients treated with potent inducers of CYP3A4 (i.e., phenytoin, carbamazepine, and rifampin), the clearance of ondansetron was significantly increased and ondansetron blood concentrations were decreased.
Mechanism: Rifampin speeds up the breakdown of ondansetron, which can make the medicine less effective.
What to do: Talk to your doctor about adjusting your dose, as the ondansetron may not work as well while taking rifampin.
In patients treated with potent inducers of CYP3A4 (i.e., phenytoin, carbamazepine, and rifampin), the clearance of ondansetron was significantly increased and ondansetron blood concentrations were decreased.
Mechanism: Phenytoin causes your body to process and remove ondansetron more quickly than usual.
What to do: Your healthcare provider might need to change your dose to ensure the medicine still works to stop nausea.
Common Questions
Can I take ondansetron for morning sickness?
Does ondansetron make you sleepy?
Can I drink alcohol while taking ondansetron?
What should I do if ondansetron doesn't work?
Can I take ondansetron with other medicines?
Is ondansetron addictive?
How long does ondansetron take to work?
Can children take ondansetron?
Does food affect how ondansetron works?
Can I drive while taking ondansetron?
What are the common side effects of ondansetron?
Does ondansetron interact with other medications?
What drug class is ondansetron?
Is ondansetron safe during pregnancy?
Has ondansetron been recalled?
Active Recalls
Defective container: Preferred Pharmaceuticals received a letter from the manufacturer Glenmark, that the blister packs are not fully sealed and tablets falling out. Preferred Pharmaceuticals purchased the finished product and repackaged the product for sale.
Glenmark Pharmaceuticals Inc., USA
Defective container: Preferred Pharmaceuticals received a letter from the manufacturer Glenmark, that the blister packs are not fully sealed and tablets falling out. Preferred Pharmaceuticals purchased the finished product and repackaged the product for sale.
Preferred Pharmaceuticals, Inc.
Related Medications in 5-HT3 Receptor Antagonist (Antiemetic)
Other drugs grouped near ondansetron — same-class peers and common alternatives.
alosetron
Lotronex
Alosetron (Lotronex) is a medicine for women with severe diarrhea-predominant irritable bowel syndrome (IBS).
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aprepitant
Emend
Aprepitant (Emend) is a medicine that helps prevent nausea and vomiting.
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bisacodyl
Dulcolax
Bisacodyl is a medicine that helps you have a bowel movement.
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bismuth subsalicylate
Pepto-Bismol
Bismuth subsalicylate (Pepto-Bismol) is a medicine that can treat diarrhea and upset stomach.
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cimetidine
Tagamet
Cimetidine (Tagamet) reduces stomach acid.
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Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
Related Health & Safety Data
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What the FDA Data Shows for ondansetron
The FDA label for ondansetron (sold under brand names such as Zofran) classifies it as a prescription-only medication in the 5-HT3 Receptor Antagonist (Antiemetic) class. This medicine is used to prevent nausea and vomiting. Official labeling lists 4 commonly reported side effects, including Headache, Feeling tired, Constipation.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 64,495 voluntary reports. The database also lists 6 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. NADAC pricing from CMS shows a generic unit cost of $0.31.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history (currently 2 recall records on file), and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: April 24, 2024
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages