Key takeaways:
Ondansetron (Zofran) is a medication that’s used to prevent nausea and vomiting. It’s available as a regular and orally disintegrating tablet, oral liquid, and injection.
Ondansetron is usually safe to take. But it does interact with some medications. This includes medications that affect serotonin levels in the brain.
Your healthcare provider can determine if it’s safe to combine other medications with ondansetron. Sharing your current medication list can help flag potential interactions.
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If you’ve ever had nausea or vomiting, you know how miserable it can be. And it can happen for many reasons, like after surgery due to anesthesia medications. It could also be caused by cancer treatments. And nausea commonly occurs during pregnancy, too. Whatever the cause, it’s always a relief when it’s prevented or goes away.
Ondansetron (Zofran) is one of the medications used to prevent some types of nausea and vomiting. You can find it as a regular and orally disintegrating tablet, oral liquid, and injection. Ondansetron works by blocking some effects of serotonin, a chemical involved in many of your body’s functions, including nausea.
Ondansetron can sometimes interact with other medications. Several ondansetron interactions are related to its effect on serotonin. And others can raise the risk of heart rhythm problems. In some cases, you may need to change medications. Others may only require monitoring. But it’s important to know what to watch out for when taking it.
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5 ondansetron interactions to know about
Several important ondansetron interactions are listed below. Keep in mind, there are other interactions not on this list.
So, it’s a good idea to check with your healthcare provider or pharmacist. They can help determine if there are serious interactions based on your other medications.
1. Selective serotonin reuptake inhibitors (SSRIs)
Selective serotonin reuptake inhibitors (SSRIs) are medications commonly used to treat depression and anxiety. Examples include sertraline (Zoloft), fluoxetine (Prozac), and paroxetine (Paxil). SSRIs are thought to work by raising serotonin levels in the brain.
As mentioned above, ondansetron also affects serotonin. This causes a possible interaction with SSRIs. Taking it with an SSRI can raise the risk of a condition called serotonin syndrome.
Serotonin syndrome is caused by serotonin levels that are too high in the brain. Most cases are mild and may not need medical care. Mild symptoms include sweating, tremors, and a fast heartbeat. But severe cases can be life-threatening. Serious symptoms include confusion, agitation, and high fever.
If you develop mild symptoms of serotonin syndrome, contact your healthcare provider. If your symptoms are severe, get immediate medical attention.
2. Serotonin and norepinephrine reuptake inhibitors (SNRIs)
Serotonin and norepinephrine reuptake inhibitors (SNRIs) are also used to treat depression and anxiety. And some SNRIs can treat nerve pain. Examples include duloxetine (Cymbalta), venlafaxine (Effexor), and desvenlafaxine (Pristiq).
Like SSRIs, SNRIs raise serotonin levels in the brain. So, they also have a risk of serotonin syndrome when combined with ondansetron. Your healthcare provider will determine if you can safely take ondansetron if you’re taking an SNRI or SSRI.
3. Other medications that affect serotonin
Besides SSRIs and SNRIs, other medications can also affect serotonin. Combining these medications with ondansetron can raise the risk of serotonin syndrome.
Examples of these medications include:
Tricyclic antidepressants (TCAs), like amitriptyline
Monoamine oxidase inhibitors (MAOIs), like selegiline (Zelapar)
Some pain medications, like meperidine
Some antibiotics, like linezolid (Zyvox)
Some dietary supplements, such as St. John’s Wort
There are lots of medications that have this risk. Talking to your healthcare provider about this interaction can be helpful. They can help you understand your risk and how to avoid it.
4. Certain antibiotics
Although rare, ondansetron can prolong the QT interval. The QT interval is the time when your heart is relaxing after receiving the electrical impulse to beat. A long QT interval can lead to heart rhythm problems.
Some antibiotics can also prolong the QT interval. Taking them with ondansetron can cause a higher chance of an irregular heartbeat. Examples of these antibiotics include:
Fluoroquinolones, like moxifloxacin (Avelox) or levofloxacin
Macrolides, like azithromycin (Zithromax) or erythromycin
A long QT interval can be life-threatening. Get immediate medical attention if you develop dizziness, sudden fainting, or blurred vision.
Sometimes a long QT interval is caused by genetics, too. In this case, ondansetron and these medications may be avoided in the first place. Otherwise, your healthcare provider will review your medical history to determine if combining these medications is OK.
5. Heart rhythm medications
This interaction is similar to what happens with certain antibiotics. Heart rhythm medications can prolong the QT interval. Combining these medications with ondansetron raises your chances of having heart rhythm problems.
Heart rhythm medications that can prolong the QT interval include:
Amiodarone (Pacerone)
Sotalol (Betapace)
Several other medications can prolong the QT interval. Your healthcare provider can check your current regimen to identify any others that might be a problem.
When should I contact my healthcare provider about an ondansetron interaction?
If you're concerned about an ondansetron interaction, contact your healthcare provider or pharmacist. You may not need to change your medications. But it doesn’t hurt to check.
Your healthcare provider may already be aware of possible ondansetron interactions. Medications are sometimes still prescribed even if there may be an interaction. Not all interactions are harmful. Some just may need extra monitoring. But some interactions can be serious.
Talk to your healthcare provider if you’re having any bothersome symptoms. This could include sweating, tremors, or irregular heartbeat. And it could mean there’s an interaction with your medications.
How can I avoid or manage potential interactions with ondansetron?
Talking with your healthcare provider in advance is one way to manage potential ondansetron interactions. They can check your medications for any serious interactions. If needed, they can also suggest safe medication changes or adjustments.
It’s also a good idea to have your medication list with you anytime you’re starting a new treatment. Your healthcare provider may already have a list of your medications. But sometimes it may be missing over-the-counter medications or supplements.
Having this information handy can help them avoid interactions if they’re prescribing a new medication. And you should make sure your pharmacist has a current medication list, too.
The bottom line
Ondansetron is an effective medication for nausea and vomiting. It’s generally safe to use with other medications. But there are a few interactions to be aware of. Examples include medications that also affect serotonin or prolong the QT interval, among others.
Contact your healthcare provider if you’re concerned about an ondansetron interaction. They can help you know what to do.
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References
Chartwell RX, LLC. (2022). Ondansetron [package insert].
Quinn, D.K., et al. (2009). Linezolid and serotonin syndrome. The Primary Care Companion to the Journal of Clinical Psychiatry.
