Can't find Ondansetron? Learn about effective alternatives like Granisetron, Palonosetron, and Promethazine that your doctor may prescribe instead.
If your pharmacy is out of Ondansetron and you need relief from nausea or vomiting, you're probably wondering: what else can I take? Whether you're dealing with chemotherapy side effects, post-surgical nausea, or morning sickness, going without an antiemetic isn't a good option.
The good news is that several effective alternatives to Ondansetron exist. In this article, we'll explain what Ondansetron is, how it works, and walk you through the best alternative medications your doctor might prescribe if you can't fill your Ondansetron prescription.
Important: Never switch medications on your own. Always talk to your doctor or pharmacist before starting a new anti-nausea medication.
Ondansetron, best known by the brand name Zofran, is a prescription antiemetic (anti-nausea medication). It's one of the most commonly prescribed anti-nausea drugs in the United States, used by millions of patients every year.
Ondansetron is FDA-approved for:
It's also widely used off-label for morning sickness during pregnancy, stomach flu, and other causes of nausea. For a complete overview of this medication, visit our guide on what Ondansetron is and how it's used.
Ondansetron belongs to a class of drugs called 5-HT3 receptor antagonists. Here's what that means in plain language:
When your body encounters triggers for nausea — like chemotherapy drugs, anesthesia, or infections — it releases a chemical called serotonin in your gut. This serotonin activates special receptors (called 5-HT3 receptors) on nerve endings, which send "vomit" signals to your brain.
Ondansetron blocks these 5-HT3 receptors, preventing the nausea signal from reaching your brain. The result: you feel less nauseous and are less likely to vomit.
For a deeper dive into this process, check out how Ondansetron works: mechanism of action explained.
If you can't get Ondansetron, these are the most common alternatives your doctor may consider. We've organized them by drug class so you can understand how they compare.
Drug class: 5-HT3 receptor antagonist (same class as Ondansetron)
How it works: Granisetron blocks the same serotonin receptors as Ondansetron, making it one of the closest substitutes available.
Available forms: Oral tablets (1 mg), injectable solution, and a transdermal patch (Sancuso) that delivers medication over 7 days.
Best for: Chemotherapy-induced nausea and vomiting, postoperative nausea. The transdermal patch is especially useful for patients who have trouble swallowing or keeping pills down.
Key differences from Ondansetron: Granisetron may be slightly less available as a generic in some areas. The patch formulation is unique and offers hands-free, continuous dosing — something Ondansetron doesn't provide.
Typical cost: Generic Granisetron tablets cost approximately $15–$40 for a short course. The Sancuso patch is significantly more expensive ($200+ per patch) without insurance.
Drug class: 5-HT3 receptor antagonist
How it works: Like Ondansetron, Palonosetron blocks 5-HT3 receptors. However, it has a much longer half-life (approximately 40 hours vs. 3-5 hours for Ondansetron), meaning a single dose lasts much longer.
Available forms: Primarily given as a single IV dose before chemotherapy. An oral capsule (Aloxi 0.5 mg) is also available.
Best for: Preventing delayed chemotherapy-induced nausea and vomiting (the nausea that starts 24+ hours after treatment). Clinical studies show Palonosetron is superior to older 5-HT3 antagonists for delayed nausea.
Key differences from Ondansetron: Palonosetron is typically used in a clinical setting (infusion centers, hospitals) rather than at home. It's more expensive but may be preferred by oncologists for certain chemotherapy regimens.
Typical cost: $300–$500 per IV dose without insurance; usually covered by insurance as part of chemotherapy treatment.
Drug class: 5-HT3 receptor antagonist
How it works: Another serotonin receptor blocker with a similar mechanism to Ondansetron.
Available forms: Oral tablets (50 mg and 100 mg). The IV formulation was withdrawn from the U.S. market due to cardiac concerns.
Best for: Prevention of chemotherapy-induced nausea and vomiting in patients who can take oral medication.
Key differences from Ondansetron: Dolasetron is less commonly prescribed than Ondansetron or Granisetron. It carries similar cardiac risks (QT prolongation). Availability may be limited.
Typical cost: $30–$80 for generic tablets.
Drug class: Phenothiazine (first-generation antihistamine/antiemetic)
How it works: Promethazine works through a completely different mechanism than Ondansetron. It blocks dopamine and histamine receptors in the brain's vomiting center, reducing nausea signals through a different pathway.
Available forms: Oral tablets (12.5 mg, 25 mg, 50 mg), rectal suppositories, injectable solution, and oral syrup.
Best for: General nausea from various causes, motion sickness, and as a backup when 5-HT3 antagonists are unavailable. Very widely available and inexpensive.
Key differences from Ondansetron: Promethazine causes significantly more drowsiness and sedation than Ondansetron. It also carries a risk of respiratory depression, especially in children under 2 (contraindicated). It's not typically first-line for chemotherapy-induced nausea but can be effective for many other causes.
Typical cost: $4–$15 for generic tablets — one of the cheapest antiemetics available.
The best alternative depends on your specific situation:
Always discuss alternatives with your doctor, who can choose the best option based on your medical history, other medications you take, and the reason you need anti-nausea treatment. Be sure to mention any heart conditions, as some of these medications can affect heart rhythm. Learn more about potential drug interactions with Ondansetron and similar medications.
If Ondansetron has been working well for you, it's worth trying to find it before switching to an alternative. Use Medfinder to search for pharmacies near you with Ondansetron in stock. You can also read our detailed guide on how to find Ondansetron in stock near you.
While Ondansetron is an excellent anti-nausea medication, it's not the only option. Granisetron, Palonosetron, Dolasetron, and Promethazine are all proven alternatives that your doctor can prescribe if you can't fill your Ondansetron prescription.
The most important thing is to not go without treatment. Nausea and vomiting — especially during chemotherapy or pregnancy — can lead to dehydration, malnutrition, and other serious complications. Talk to your healthcare provider promptly if you're unable to find your medication.
For the latest on availability and pricing, visit our Ondansetron shortage update for 2026 and our guide to saving money on Ondansetron.
You focus on staying healthy. We'll handle the rest.
Try Medfinder Concierge FreeMedfinder's mission is to ensure every patient gets access to the medications they need. We believe this begins with trustworthy information. Our core values guide everything we do, including the standards that shape the accuracy, transparency, and quality of our content. We’re committed to delivering information that’s evidence-based, regularly updated, and easy to understand. For more details on our editorial process, see here.
%2C%20Color%3DOriginal.png)
