Ondansetron for Dogs – What is it [Used] for?

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Published by Catharina Hjorth

Updated on

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Can Dogs Take Ondansetron? 

Ondansetron for dogs is a type of antiemetic – meaning a veterinarian prescribes it to treat nausea and vomiting in dogs and cats, if necessary.  

It is an “off-label” medication made for humans, but that doesn’t mean dogs can’t take it. On the contrary, veterinarians frequently prescribe off-label medications. It just means you have to follow your veterinarian’s instructions closely, as the information found on the medicine may not be relevant for your dog. 

But, under the guidance of a veterinarian, it becomes Ondansetron dog medication and can be just what your dog needs to get back on its feet! 


What is Ondansetron for Dogs?

Luckily, several antiemetics (anti-vomiting) and anti-nausea medications are available. The various drugs have different ways of working, but typical for them all is that they inhibit the neurotransmitter that makes the brain think it needs to vomit. Some can even alleviate some nausea a dog is experiencing when sick. 

The more nerdy explanation is that Ondansentron for dogs works by selectively inhibiting receptors within the body called 5HT3 receptors. Inhibiting these receptors then blocks the chemical release of a neurotransmitter called serotonin within the gastrointestinal tract and a brain region called the chemoreceptor trigger zone. 

The release of serotonin is what can cause nausea and vomiting. Blocking its release helps alleviate the feeling of being ill and can even stop vomiting ultimately. 

Ondansetron Dose for Dogs

You should not administer Ondansetron without consulting a veterinarian first, as the doses and duration needed may vary a lot, depending on your dog’s condition and other factors. 

Ondansetron for dogs is available as three different types of tablets, in the strength of:

  • 4 mg. 
  • 8 mg.
  • 24 mg.

Your veterinarian can also prescribe an oral solution in 4 mg/ml strength. 

The usual Ondansetron dose for dogs is 0.05 to 0.5 mg/pound (0.1 to 1.0 mg/kg) to be given orally (through the mouth) once or twice per day. You can administer Ondansetron with or without food; however, future doses should not be administered on an empty stomach if vomiting occurs.  

Even a relatively low Ondansentron dose for dogs should take effect quickly, within 1 to 2 hours, with clinical signs improving or resolving soon after that. 

Ondansetron for Dogs – Side Effects

Ondansetron underwent careful evaluation in trials replicated several times and is generally considered safe. In clinical studies, Ondansetron doses 30 to 100 times stronger than recommended showed no significant side effects. 

However, some dogs may experience side effects. The most common Ondansetron for dogs’ side effects reported can include constipation and tiredness. Other rare side effects include abnormal heart rhythms and low blood pressure. 

Ondansetron is considered a safe medication, and no extra monitoring is necessary when your dog receives it. However, your veterinarian may, of course, want to monitor that your dog is getting better on the medication. 

dog with vomit

What if I Forget to Give my Dog Ondansetron?

If you have missed a dose of Ondansetron, you can give it when you remember. If you are close to when you should provide the next amount, skip the missed dose and give the next one at the scheduled time.

Although being nauseated and vomiting can be extremely uncomfortable, it is unlikely that one missed dose will significantly harm your dog. If you are in doubt about your dog’s condition, contact your veterinary care provider, 

Ondansetron for Dogs – The Risk Factors

As with all animal medications, don’t use them in animals allergic to the active ingredients. If your dog has previously experienced an untoward reaction to Ondansetron, be sure to advise your veterinarian. 

Ondansetron for dogs can, in rare cases, affect the heart rhythm and is therefore only cautiously used in animals with certain abnormal heart rhythms. 

Caution is also advisable when Ondansetron is administered to animals with gastrointestinal blockage, liver disease, or pregnant or lactating females. Previous research does not establish whether it is safe. 

Some dog breeds, like collies, sheepdogs, and crosses involving these, may have a genetic mutation in their MDR1 gene. The mutation can mean they have a lower tolerance of some medications, including Ondansetron for dogs, and caution is necessary when using the drug for these breeds. 

Canine Ondansetron and Potential Drug Interactions

All drugs can – to some extent – interact with some other medicines, including Ondansetron. Therefore, you must inform your veterinarian about any medication, vitamins, supplements, or herbal additives your dog may take. Your veterinarian will know to be aware of any interactions. 

Ondansetron can interact with other drugs, including: 

  • Certain heart medications. 
  • Tramadol (pain medication). 
  • Cyclophosphamide (a chemotherapy medication). 
  • Cisplatin (a medicine sometimes used in cancer treatment). 

How to Store Ondansetron for Dogs

It would be best if you stored Ondansetron at room temperature between 2 to 30 degrees Celcius (36 to 86 Fahrenheit). The medication also needs to be kept away from light and moisture. 

What to do in Case of Emergency

If you are worried about your dog’s health condition, you should contact your veterinarian immediately. 

Suppose you suspect your dog is experiencing an overdose or adverse reaction to the Ondansetron. In that case, you also need to call a veterinary care facility and discuss the best option for you and your dog. Remember to inform them about the following: 

  • Identify you and your dog (especially if this is not your regular veterinary care provider). 
  • When was the last time you gave your dog Ondansetron?
  • How much Ondansetron did you give? 
  • What symptoms is your dog suffering from currently? 

Inform them of the above, and they should be able to help you as soon as possible.  

Can Dogs Take Human Ondansetron?

Ondansetron is a human drug, meaning you can give your dog Ondansetron prescribed to humans – in theory. 

However, it is not advisable to give your dog Ondansetron not prescribed by a veterinarian. The information you will find on the Ondansetron medication will not be the correct dose or treatment length for dogs. 

Dog vomit in the living room

The Final Bark

We all want our furry friends to feel happy and comfortable – preferably as soon as possible! So when a veterinarian prescribes Ondansetron for dogs, it is an excellent drug to help treat our nauseous and vomiting animals and get help them back on their feet, sooner rather than later! 

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With a veterinary master's degree from the University of Copenhagen in 2023, this accomplished writer's academic journey culminated in a thesis focused on the "Feasibility of using ultrasound of the abdomen for early diagnosis of necrotizing enterocolitis in neonatal pigs." Additionally, their dissertation delved into the intriguing topic of "Mercury accumulation in Greenlandic sleddogs." Beyond her academic achievements, her passion for animal health seamlessly merges with her love for writing. She excels in harmonizing clinical precision with literary expression, crafting articles that resonate with the heartbeat of her veterinary profession.


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