{"shortAnswer":"Ondansetron, sold as Zofran, is FDA-approved to prevent nausea and vomiting from cancer treatment and surgery. For that use the evidence grade is strong-human. Its use for nausea in pregnancy is not approved. It can upset the heart's rhythm.","url":"https://peptideindex.ai/compound/ondansetron","status":"fda-approved","statusCheckedAt":"2026-10-26T13:43:50.985Z","statusStale":false,"regulatoryAsOf":"2026-10-26","verified":"2026-10-26T13:43:51.014Z","primarySourceUrl":"https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020103","clinicallyReviewed":false,"notice":"Information, not medical advice.","id":"af0dd913-6297-4fbf-a2aa-462be991c611","object":"compound","slug":"ondansetron","name":"Ondansetron","attrs":{"name":"Ondansetron","class":"non-peptide","access":[{"type":"approved-product","detail":"Approved by FDA as a prescription drug. Drugs@FDA lists the Zofran brand products as no longer sold.","indication":"Prevention of nausea and vomiting from cancer chemotherapy, radiotherapy and surgery.","source_url":"https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020103","brand_names":["Zofran","Zofran ODT"],"manufacturer":"Sandoz"},{"type":"lawful-compounding","detail":"Pharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug.","source_url":"https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act"}],"dosing":"From the Zofran labels. By mouth, adults take a single 24 mg dose 30 minutes before highly nausea-causing chemotherapy. Before other chemotherapy, adults take 8 mg 30 minutes before it and 8 mg 8 hours later. Then they take 8 mg every 12 hours for 1 to 2 days after it ends. Before surgery, adults take 16 mg an hour before anesthesia. By vein before chemotherapy, the dose is 0.15 mg per kilogram, up to 16 mg, given three times. People with severe liver disease take no more than 8 mg a day. The prescriber sets the dose.","trials":[{"nct":"NCT05784350","url":"https://clinicaltrials.gov/study/NCT05784350","phase":"Not applicable","title":"Preoperative Point of Care Ultrasound Guided Fluid Optimization and Intravenous Ondansetron to Prevent General Anesthesia-Induced Hypotension","status":"not-yet-recruiting","sponsor":"Meir Medical Center","countries":["Israel"],"us_states":[]},{"nct":"NCT07891312","url":"https://clinicaltrials.gov/study/NCT07891312","phase":"Not applicable","title":"Amisulpride Injection for the Prevention of Postoperative Nausea and Vomiting in Patients Undergoing Laparoscopic Surgery","status":"not-yet-recruiting","sponsor":"Qianfoshan Hospital","countries":[],"us_states":[]},{"nct":"NCT07795060","url":"https://clinicaltrials.gov/study/NCT07795060","phase":"Phase 2","title":"Ondansetron to Prevent Oral Rehydration Failure in Children With Cholera","status":"not-yet-recruiting","sponsor":"Public Interest Science Center","countries":["Republic of the Congo"],"us_states":[]},{"nct":"NCT07588217","url":"https://clinicaltrials.gov/study/NCT07588217","phase":"Phase 2/Phase 3","title":"Ondansetron for the Prevention of Patient Self-Inflicted Lung Injury in Patients With ARDS - Pilot RCT","status":"not-yet-recruiting","sponsor":"Centre Integre Universitaire de Sante et Services Sociaux du Nord de l'ile de Montreal","countries":["Canada"],"us_states":[]},{"nct":"NCT07848984","url":"https://clinicaltrials.gov/study/NCT07848984","phase":"Phase 2","title":"Chinese Herbal Acupoint Application Combined With Triple Antiemetic Therapy for Prevention of Chemotherapy-Induced Nausea and Vomiting in Breast Cancer","status":"not-yet-recruiting","sponsor":"Second Affiliated Hospital, Zhejiang University, School of Medicine","countries":["China"],"us_states":[]},{"nct":"NCT07793760","url":"https://clinicaltrials.gov/study/NCT07793760","phase":"Phase 4","title":"Dexamethasone Versus Ondansetron for Preventing Post-Spinal Hypotension in Preeclampsia","status":"not-yet-recruiting","sponsor":"Assiut University","countries":[],"us_states":[]},{"nct":"NCT07858149","url":"https://clinicaltrials.gov/study/NCT07858149","phase":"Phase 4","title":"Effects of Ondansetron Timing During Spinal Anesthesia for Urologic Surgery","status":"not-yet-recruiting","sponsor":"Istanbul University","countries":["Turkey (Türkiye)"],"us_states":[]},{"nct":"NCT07868861","url":"https://clinicaltrials.gov/study/NCT07868861","phase":"Phase 1","title":"A Study to Compare the Bioavailability of Ondansetron Following Nasal (NS003) and IV Administration in Healthy Adults","status":"recruiting","sponsor":"Nasus Pharma","countries":["Israel"],"us_states":[]},{"nct":"NCT07813975","url":"https://clinicaltrials.gov/study/NCT07813975","phase":"Not applicable","title":"Evaluating the Impact of Vitamin D Supplementation on Healing Bed Sores in ICU.","status":"recruiting","sponsor":"Maha Salah","countries":["Egypt"],"us_states":[]},{"nct":"NCT07681076","url":"https://clinicaltrials.gov/study/NCT07681076","phase":"Phase 4","title":"Study to Assess Safety and Tolerability of KarXT With Administration of Antiemetics in Healthy Volunteers","status":"recruiting","sponsor":"Karuna Therapeutics, Inc., a Bristol Myers Squibb company","countries":["United States"],"us_states":["California","Florida","Georgia"]},{"nct":"NCT07761312","url":"https://clinicaltrials.gov/study/NCT07761312","phase":"Phase 4","title":"Afentanil and Remifentanil for Anesthesia Quality and Recovery","status":"not-yet-recruiting","sponsor":"Qianfoshan Hospital","countries":[],"us_states":[]},{"nct":"NCT07638527","url":"https://clinicaltrials.gov/study/NCT07638527","phase":"Phase 4","title":"Time to First Rescue Antiemetic With Ondansetron Plus Metoclopramide Versus Dexamethasone Plus Metoclopramide for PONV Prophylaxis in Laparoscopic Cholecystectomy","status":"recruiting","sponsor":"Faisalabad Medical University","countries":["Pakistan"],"us_states":[]},{"nct":"NCT07777276","url":"https://clinicaltrials.gov/study/NCT07777276","phase":"Phase 4","title":"Sleep Quality - Comparing the Effect of Ondansetron or Dexamethasone Given as Routine Prophylaxis Intraoperatively to Prevent Post Operative Nausea and Vomiting (SCORPION)","status":"not-yet-recruiting","sponsor":"Telethon Kids Institute","countries":["Australia","Brazil"],"us_states":[]},{"nct":"NCT07662200","url":"https://clinicaltrials.gov/study/NCT07662200","phase":"Early phase 1","title":"A Simplified Regimen to Prevent Nausea and Vomiting Using Netupitant/Palonosetron in Germ Cell Cancer Patients Receiving Chemotherapy","status":"not-yet-recruiting","sponsor":"Ottawa Hospital Research Institute","countries":["Canada"],"us_states":[]},{"nct":"NCT07740577","url":"https://clinicaltrials.gov/study/NCT07740577","phase":"Phase 4","title":"Routine Antiemetic Prophylaxis for Nonfasted Parturients Undergoing Cesarean Sections Under Spinal Anesthesia","status":"recruiting","sponsor":"Sanliurfa Education and Research Hospital","countries":["Turkey (Türkiye)"],"us_states":[]},{"nct":"NCT07697625","url":"https://clinicaltrials.gov/study/NCT07697625","phase":"Phase 1","title":"A Clinical Trial of MK-4082 in Healthy Participants (MK-4082-005)","status":"recruiting","sponsor":"Merck Sharp & Dohme LLC","countries":["United States"],"us_states":["California"]},{"nct":"NCT07768124","url":"https://clinicaltrials.gov/study/NCT07768124","phase":"Not applicable","title":"Acupoint Application for Chemotherapy-Induced Nausea and Vomiting in Lung Cancer","status":"recruiting","sponsor":"Xiu Huang","countries":["China"],"us_states":[]},{"nct":"NCT07639723","url":"https://clinicaltrials.gov/study/NCT07639723","phase":"Phase 4","title":"Aprepitant to Improve Same Day Discharge for TKA","status":"not-yet-recruiting","sponsor":"Endeavor Health","countries":["United States"],"us_states":["Illinois"]},{"nct":"NCT07643285","url":"https://clinicaltrials.gov/study/NCT07643285","phase":"Not applicable","title":"Feasibility and Safety of a Pediatric ERAS Protocol for Laparoscopic Appendectomy","status":"recruiting","sponsor":"Ahmet Burak Doğan, MD","countries":["Turkey (Türkiye)"],"us_states":[]},{"nct":"NCT07632144","url":"https://clinicaltrials.gov/study/NCT07632144","phase":"Not applicable","title":"Ondansetron Versus Lidocaine for Preventing Pain on Propofol Injection.","status":"not-yet-recruiting","sponsor":"Mongi Slim Hospital","countries":["Tunisia"],"us_states":[]},{"nct":"NCT07706348","url":"https://clinicaltrials.gov/study/NCT07706348","phase":"Phase 1/Phase 2","title":"Intraperitoneal Irrigation of Ondansteron in Combination With Lidocaine in Acute Postoperative Pain","status":"recruiting","sponsor":"Assiut University","countries":["Egypt"],"us_states":[]},{"nct":"NCT07558226","url":"https://clinicaltrials.gov/study/NCT07558226","phase":"Not applicable","title":"Multimodal Anesthesia in Robotic Laparoscopic Nephrectomy","status":"recruiting","sponsor":"Fundacio Puigvert","countries":["Spain"],"us_states":[]},{"nct":"NCT07603596","url":"https://clinicaltrials.gov/study/NCT07603596","phase":"Phase 1","title":"Opioid-free Anesthesia and Postoperative Delirium","status":"not-yet-recruiting","sponsor":"Qianfoshan Hospital","countries":[],"us_states":[]},{"nct":"NCT07381634","url":"https://clinicaltrials.gov/study/NCT07381634","phase":"Phase 2","title":"The Safety and Efficacy of Ondansetron in Reducing Immune Checkpoint Inhibitor-Related Toxicities","status":"recruiting","sponsor":"First Affiliated Hospital of Wenzhou Medical University","countries":["China"],"us_states":[]},{"nct":"NCT07511491","url":"https://clinicaltrials.gov/study/NCT07511491","phase":"Not applicable","title":"Ondansetron Lozenge Versus Intravenous for Prevention of Shivering in Cesarean Section","status":"recruiting","sponsor":"Tanta University","countries":["Egypt"],"us_states":[]},{"nct":"NCT07455955","url":"https://clinicaltrials.gov/study/NCT07455955","phase":"Phase 2","title":"Personalized Antiemetic Regimen According to Patients' Pharmacogenetic Profile","status":"recruiting","sponsor":"Chinese University of Hong Kong","countries":["Hong Kong"],"us_states":[]},{"nct":"NCT07489742","url":"https://clinicaltrials.gov/study/NCT07489742","phase":"Not applicable","title":"Ondansetron Lozenge Versus Intravenous for Prevention of Shivering in Tonsillectomy","status":"recruiting","sponsor":"Tanta University","countries":["Egypt"],"us_states":[]},{"nct":"NCT07458295","url":"https://clinicaltrials.gov/study/NCT07458295","phase":"Not applicable","title":"The Efficacy and Safety of Liposomal Bupivacaine for Transversus Abdominis Plane Block in Relieving Postoperative Pain After Laparoscopic Surgery in Gynecologic Oncology","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07458282","url":"https://clinicaltrials.gov/study/NCT07458282","phase":"Not applicable","title":"The Efficacy and Safety of Liposomal Bupivacaine for Transversus Abdominis Plane Block in Relieving Postoperative Pain After Laparoscopic Surgery","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07458256","url":"https://clinicaltrials.gov/study/NCT07458256","phase":"Not applicable","title":"The Efficacy and Safety of Liposomal Bupivacaine in Relieving Postoperative Pain After Laparoscopic Surgery","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07442539","url":"https://clinicaltrials.gov/study/NCT07442539","phase":"Not applicable","title":"The Efficacy and Safety of Liposomal Bupivacaine in Relieving Postoperative Pain After Hemorrhoid Surgery","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07432711","url":"https://clinicaltrials.gov/study/NCT07432711","phase":"Not applicable","title":"The Efficacy and Safety of Liposomal Bupivacaine in Relieving Postoperative Pain After Video-assisted Thoracoscopic Surgery","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07441902","url":"https://clinicaltrials.gov/study/NCT07441902","phase":"Not applicable","title":"The Efficacy and Safety of Liposomal Bupivacaine for Rhomboid Intercostal Nerve Block in Relieving Postoperative Pain After Video-assisted Thoracoscopic Surgery","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07330999","url":"https://clinicaltrials.gov/study/NCT07330999","phase":"Not applicable","title":"Three Variants of the PENG Block With and Without Perineural Adjuvants in Older Adults","status":"recruiting","sponsor":"Poznan University of Medical Sciences","countries":["Poland"],"us_states":[]},{"nct":"NCT07699276","url":"https://clinicaltrials.gov/study/NCT07699276","phase":"Phase 2","title":"Steroid Sparing Regimen With Olanzapine and Palonosetron for Emetic Prevention for High Dose Cisplatin","status":"recruiting","sponsor":"Mahidol University","countries":["Thailand"],"us_states":[]},{"nct":"NCT07377903","url":"https://clinicaltrials.gov/study/NCT07377903","phase":"Not applicable","title":"Post Operative Shivering Following Anesthesia","status":"not-yet-recruiting","sponsor":"Sohag University","countries":[],"us_states":[]},{"nct":"NCT07607990","url":"https://clinicaltrials.gov/study/NCT07607990","phase":"Not applicable","title":"Effects of Rectal Indomethacin Suppository on Postoperative CRBD in Patients Undergoing LRP","status":"recruiting","sponsor":"Zhejiang University","countries":["China"],"us_states":[]},{"nct":"NCT07361822","url":"https://clinicaltrials.gov/study/NCT07361822","phase":"Not applicable","title":"Comparison of Cumulative Opioid Consumption Between Variable-Rate Feedback Infusion and Fixed-Rate Basal Infusion Modes of Intravenous PCA Following Mixed Surgery","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07375121","url":"https://clinicaltrials.gov/study/NCT07375121","phase":"Not applicable","title":"Comparison of the Efficacy and Safety of Fixed-rate Basal Infusion Mode and Time-programmed Decremental Background Infusion Mode of Intravenous PCA Following Mixed Surgery","status":"recruiting","sponsor":"Beijing Tiantan Hospital","countries":["China"],"us_states":[]},{"nct":"NCT07246070","url":"https://clinicaltrials.gov/study/NCT07246070","phase":"Phase 2","title":"Nano-crystalline Megestrol Acetate for Chemotherapy-induced Nausea and Vomiting","status":"not-yet-recruiting","sponsor":"AIPING ZHOU","countries":[],"us_states":[]},{"nct":"NCT06869967","url":"https://clinicaltrials.gov/study/NCT06869967","phase":"Not applicable","title":"Evaluation of Postoperative Pain Control in Ear Surgery","status":"recruiting","sponsor":"Kocaeli University","countries":["Turkey (Türkiye)"],"us_states":[]},{"nct":"NCT06953570","url":"https://clinicaltrials.gov/study/NCT06953570","phase":"Not stated","title":"Impact of Frailty on Nalbuphine Dose for Postoperative Analgesia in Elderly Patients Undergoing Laparoscopic GI Surgery","status":"not-yet-recruiting","sponsor":"Yongtao Sun","countries":[],"us_states":[]},{"nct":"NCT07164677","url":"https://clinicaltrials.gov/study/NCT07164677","phase":"Not applicable","title":"Serratus Posterior Superior Plane Block for Postoperative Pain in Cardiac Surgery","status":"recruiting","sponsor":"Ondokuz Mayıs University","countries":["Turkey (Türkiye)"],"us_states":[]},{"nct":"NCT06952920","url":"https://clinicaltrials.gov/study/NCT06952920","phase":"Phase 3","title":"Electroacupuncture for Chemotherapy-Induced GI Symptom Clusters in Breast Cancer","status":"recruiting","sponsor":"Jiuda Zhao","countries":["China"],"us_states":[]},{"nct":"NCT07124195","url":"https://clinicaltrials.gov/study/NCT07124195","phase":"Phase 3","title":"Nanocrystalline Megestrol for Managing Chemotherapy-Induced Nausea and Vomiting","status":"not-yet-recruiting","sponsor":"The First Affiliated Hospital of Xinxiang Medical College","countries":["China"],"us_states":[]},{"nct":"NCT07088601","url":"https://clinicaltrials.gov/study/NCT07088601","phase":"Phase 4","title":"Efficacy of Oral Ondansetron Strips on Prevention of Post-Spinal Shivering","status":"not-yet-recruiting","sponsor":"Cairo University","countries":[],"us_states":[]},{"nct":"NCT06530563","url":"https://clinicaltrials.gov/study/NCT06530563","phase":"Phase 4","title":"the Efficacy and Safety of Oliceridine Fumarate Injection for Acute Pain After Abdominal Surgery","status":"not-yet-recruiting","sponsor":"Xiangya Hospital of Central South University","countries":["China"],"us_states":[]},{"nct":"NCT07084753","url":"https://clinicaltrials.gov/study/NCT07084753","phase":"Not applicable","title":"Non-opioid Anesthesia Based on Thoracic Paravertebral Block During Laparoscopic Sleeve Gastrectomy","status":"not-yet-recruiting","sponsor":"IVO JURISIC","countries":["Croatia"],"us_states":[]},{"nct":"NCT06938581","url":"https://clinicaltrials.gov/study/NCT06938581","phase":"Not applicable","title":"ERAS Protocols in Breast Conserving Surgery","status":"recruiting","sponsor":"University of Nebraska","countries":["United States"],"us_states":["Nebraska"]},{"nct":"NCT06904235","url":"https://clinicaltrials.gov/study/NCT06904235","phase":"Phase 2","title":"Study With IV NEPA (Fosnetupitant/Palonosetron) for the Prevention of Chemotherapy-induced Nausea and Vomiting in Paediatric Cancer Patients Undergoing Highly Emetogenic Chemotherapy (HEC)","status":"recruiting","sponsor":"Helsinn Healthcare SA","countries":["Greece","Poland","Romania","Turkey (Türkiye)"],"us_states":[]}],"aliases":["Zofran","Zofran ODT","ondansetron hydrochloride"],"summary":"A prescription drug that prevents nausea and vomiting from cancer treatment and surgery. Zofran is its brand name.","citations":[{"n":1,"url":"https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/020103s039,020605s023,020781s023lbl.pdf","tier":"primary","type":"label","title":"Zofran tablets, orally disintegrating tablets and oral solution label, revised February 2025"},{"n":2,"url":"https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/020007s050lbl.pdf","tier":"primary","type":"label","title":"Zofran injection label, revised February 2025"},{"n":3,"url":"https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020103","tier":"primary","type":"regulatory","title":"Drugs@FDA: Zofran (ondansetron hydrochloride) tablets, application 020103"},{"n":4,"url":"https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020007","tier":"primary","type":"regulatory","title":"Drugs@FDA: Zofran (ondansetron hydrochloride) injection, application 020007"},{"n":5,"url":"https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=020781","tier":"primary","type":"regulatory","title":"Drugs@FDA: Zofran ODT (ondansetron) orally disintegrating tablets, application 020781"},{"n":6,"url":"https://www.federalregister.gov/documents/2015/06/10/2015-14145/determination-that-ondansetron-ondansetron-hydrochloride-injection-usp-in-pl-2408-plastic-container","tier":"primary","type":"regulatory","title":"Federal Register: 32 mg single-dose ondansetron injection withdrawn from sale for reasons of safety, 10 June 2015"},{"n":7,"url":"https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act","tier":"primary","type":"regulatory","title":"FDA: bulk drug substances used in compounding under section 503A"},{"n":8,"url":"https://www.fda.gov/media/94155/download","tier":"primary","type":"regulatory","title":"FDA: 503A bulk drug substances category list, updated May 2026"},{"n":9,"url":"https://pubmed.ncbi.nlm.nih.gov/30561479/","tier":"peer-reviewed","type":"human-trial","title":"Cohort study: first-trimester ondansetron, heart defects and oral clefts in US Medicaid pregnancies, 2018"},{"n":10,"url":"https://pubmed.ncbi.nlm.nih.gov/23445092/","tier":"peer-reviewed","type":"human-trial","title":"Cohort study: ondansetron in pregnancy and fetal outcomes in Denmark, 2013"},{"n":11,"url":"https://pubmed.ncbi.nlm.nih.gov/16625009/","tier":"peer-reviewed","type":"rct","title":"Randomized trial: oral ondansetron for gastroenteritis in a pediatric emergency department, 2006"},{"n":12,"url":"https://pubmed.ncbi.nlm.nih.gov/21901699/","tier":"peer-reviewed","type":"systematic-review","title":"Cochrane review: antiemetics for vomiting from gastroenteritis in children, 2011"},{"n":13,"url":"https://pubmed.ncbi.nlm.nih.gov/33075160/","tier":"peer-reviewed","type":"systematic-review","title":"Cochrane network meta-analysis: drugs to prevent nausea and vomiting after surgery, 2020"},{"n":14,"url":"https://pubmed.ncbi.nlm.nih.gov/27701665/","tier":"peer-reviewed","type":"systematic-review","title":"Systematic review: treatments for nausea and vomiting in pregnancy, 2016"},{"n":15,"url":"https://pubmed.ncbi.nlm.nih.gov/25198265/","tier":"peer-reviewed","type":"rct","title":"Randomized trial: ondansetron against doxylamine and pyridoxine for nausea in pregnancy, 2014"},{"n":16,"url":"https://pubmed.ncbi.nlm.nih.gov/36737400/","tier":"peer-reviewed","type":"animal","title":"Rat study: embryo-fetal safety of ondansetron, 2023"},{"n":17,"url":"https://www.druganddevicelawblog.com/2023/01/mdl-wide-preemption-win-in-zofran-affirmed.html","tier":"legal-analysis","type":"legal-analysis","title":"Drug and Device Law: appeals court upholds preemption in the Zofran cases, January 2023"},{"n":18,"url":"https://news.bloomberglaw.com/litigation/gsk-zofran-birth-injury-lawsuits-preempted-by-federal-law","tier":"established-news","type":"reference","title":"Bloomberg Law: Zofran birth injury lawsuits preempted by federal law, January 2023"},{"n":19,"url":"https://clinicaltrials.gov/study/NCT06382012","tier":"primary","type":"reference","title":"ClinicalTrials.gov NCT06382012: fosaprepitant against ondansetron for nausea and vomiting"}],"known_risks":["It can change the heart's electrical rhythm, called QT prolongation. Rare cases of a deadly rhythm, torsade de pointes, have been reported [^1] [^2].","FDA found that a 32 mg single dose into a vein was pulled from sale for reasons of safety. That dose raised the heart rhythm risk [^6].","Serotonin syndrome has been reported, mostly in people who also took some antidepressants or opioids. Some cases were fatal [^1].","Taken with apomorphine, it can cause a big drop in blood pressure and passing out. The label says not to combine them [^1].","Some people have had bad allergic reactions. A few had trouble breathing [^1].","Reduced blood flow to the heart has been reported, mostly when it was given into a vein [^1].","After belly surgery or cancer drugs, it can hide a blocked bowel [^1].","In the label's studies, the most common problems were headache and feeling tired. Others were constipation and diarrhea [^1].","A 2018 US study of 1.8 million pregnancies found a small rise in oral clefts, a split lip or palate, with use in the first three months [^9]."],"short_answer":"Ondansetron, sold as Zofran, is FDA-approved to prevent nausea and vomiting from cancer treatment and surgery. For that use the evidence grade is strong-human. Its use for nausea in pregnancy is not approved. It can upset the heart's rhythm.","evidence_grade":"strong-human","open_questions":["Nobody knows for sure if it harms a baby in early pregnancy. The label says studies have found mixed results [^1] [^9] [^10].","A 2016 review of nausea in pregnancy found the evidence was of low quality [^14].","The 2014 trial in pregnant women was small. Only 36 women took part [^15].","After surgery, a 2020 review found only low or very low certainty about serious harms. It called for more studies of harms [^13]."],"section_routes":"The legal way to get ondansetron is a prescription [^1] [^2]. Its labels cover nausea and vomiting from cancer drugs, radiation and surgery [^1] [^2]. The Zofran brand products are listed as no longer sold [^3] [^4] [^5].\n\nPharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug [^7].\n\nUS trials that use ondansetron are open, such as one comparing it with fosaprepitant for nausea [^19]. The trials block on this page lists open trials with their dates.","regulatory_as_of":"2026-10-26","section_evidence":"The evidence grade is strong-human for stopping vomiting after surgery and from a stomach bug in children [^11] [^13]. A 2020 review pooled 585 studies of drugs used during surgery [^13]. It found high-certainty evidence that ondansetron cuts vomiting in the first day [^13].\n\nIn a 2006 trial, 215 children with a stomach bug got one dose or a dummy pill [^11]. Of those on the drug, 14% vomited, against 35% on the dummy pill [^11]. A 2011 review of seven trials found it cut the need for a drip and a hospital stay [^12].\n\nFor nausea in pregnancy, a 2016 review linked it to fewer symptoms [^14]. The review rated the evidence as low quality [^14]. In a 2014 trial of 36 women, it eased nausea more than doxylamine and pyridoxine [^15].\n\nOn safety in pregnancy, studies disagree. A 2013 study of pregnancies in Denmark found no rise in birth defects or miscarriage [^10]. A 2018 US study found a small rise in oral clefts [^9]. A 2023 study in rats found no birth defects in the pups [^16].","regulatory_status":"fda-approved","section_what_it_is":"Ondansetron is a drug that prevents nausea and vomiting [^1]. It blocks one kind of serotonin receptor, called 5-HT3 [^1]. It is not a peptide.\n\nIt comes as a tablet, a tablet that melts on the tongue, a liquid to swallow and a shot [^1] [^2]. Zofran is the brand name [^1]. FDA first approved it in 1991 [^1].","section_is_it_legal":"Ondansetron is FDA-approved: Drugs@FDA lists Zofran tablets, Zofran shots and Zofran tablets that melt on the tongue as approved drugs [^3] [^4] [^5]. The approval covers nausea and vomiting from cancer drugs, radiation and surgery [^1] [^2]. It does not cover nausea in pregnancy, which is an off-label use [^17] [^18]. Checked 26 October 2026.\n\nDrugs@FDA lists the Zofran brand products as no longer sold. A Federal Register notice says they were not pulled for safety reasons [^3] [^4] [^5]. One high dose was different. In 2015, FDA found that a 32 mg single dose into a vein was pulled from sale for reasons of safety [^6].\n\nIn 2023, a federal appeals court upheld the dismissal of hundreds of birth defect lawsuits [^17] [^18]. It found FDA would have rejected the pregnancy warning the families wanted [^18].\n\nPharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug [^7]. Ondansetron is not on FDA's 503A category list 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