Background
Ondansetron (aka Zofran) is a 5-HT3 (serotonin type 3) receptor antagonist used to treat severe nausea and vomiting in humans. It has recently been shown to be very effective in cats as well and comes as both a tablet and an injection for subcutaneous use. As it is not licensed in cats, it is not our first choice when it comes to treating nausea but it can be very useful for those cats that fail to respond to Cerenia.
How this Medication is Used
Ondansetron is used exclusively to treat nausea and vomiting, there are no other known benefits. The tablets may be given with or without food.
Some cats find it particularly distasteful so we do not recommend crushing it (although you are welcome to try as all cats are different), rather wrap it tightly inside a small amount of treat and then give as you normally would any tablet. If your cat gets a taste of it, they may start to hypersalivate – this isn’t particularly nice for them or for you to watch, but it is not dangerous and will pass once the taste fades so just wipe their mouth and offer some plain food and water and try a different method of hiding the pill next time!
If given subcutaneously, some cats find that the injection stings a bit, others don’t seem to notice. In most cases this is not significant enough to justify discontinuing the medication.
There is a wide margin of safety and efficacy when it comes to dosing ondansetron. When given orally, the average cat can have between 2-4mg, 2-4 times a day so it may take a few days to find out which dose best suits your cat.
Side Effects
Ondansetron appears to be well tolerated by cats. Constipation, sedation, head shaking, arrhythmias and hypotension are possible but rare side effects, please let us know if you notice anything unusual after giving ondansetron to your cat.
Interactions with Other Drugs
Ondansetron probably should not be given alongside cisapride or right before a general anaesthetic due to possible effects on the heart, although this a theoretical concern and hasn’t been an issue in practice.
Ondansetron may also interfere with the effectiveness of tramadol (a pain killer not often used in cats).
Concerns and Cautions
- Ondansetron should be used with caution in patients with liver dysfunction. This is not to say that they cannot have it, but we may need to decrease the dose as it is metabolized by the liver.
Please do not hesitate to get in touch if you have any concerns about giving your cat ondansetron.