What is ondansetron?
Ondansetron (brand names Zofran®, Zuplenz®) is an antiemetic used off label (extra label) to treat severe nausea and vomiting in dogs and cats.
Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
How is ondansetron given?
- Ondansetron is given by mouth in the form of a tablet or liquid.
- Measure liquids carefully.
- Some tablets dissolve, so be sure your hands are dry before handling these tablets.
- It may be given with or without food. If vomiting occurs when dosed on an empty stomach, give future doses with food or a treat.
- In the hospital, it is also administered via injectable liquid and given in the vein, muscle, or under the skin.
This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.
What if I miss giving my pet the medication?
If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.
Are there any potential side effects?
Ondansetron may cause the following side effects, rarely:
- constipation
- sleepiness
- head shaking
Serious but rare adverse reactions may occur. If any of the following signs develop, stop giving ondansetron and contact your veterinarian immediately:
- abnormal heart rhythms
- fainting/collapse or severe lethargy due to low blood pressure
This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.
Are there any risk factors for this medication?
Ondansetron should NOT BE USED in pets that are allergic to it.
Ondansetron should be USED WITH CAUTION in pets that:
- have a gastrointestinal blockage
- have certain abnormal heart rhythms
- have liver disease
- are pregnant or lactating (safety has not been clearly established)
Some breeds of dogs (e.g., collies, sheepdogs, and collie- or sheepdog-cross breeds) have a specific genetic mutation (MDR1) that makes them less able to tolerate certain medications. Therefore, ondansetron should be USED WITH CAUTION in MDR1-positive dogs.
Are there any drug interactions I should be aware of?
The following medications should be used with caution when given with ondansetron:
- apomorphine
- certain heart medications
- cyclophosphamide
- serotonergic drugs
- tramadol
Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.
Is any monitoring needed with this medication?
- No specific monitoring is required while your pet is taking this medication.
- Your veterinarian may monitor your pet to be sure that the medication is working.
How do I store ondansetron?
- Store this medication at room temperature between 2°C and 30°C (36°F and 86°F) in a tight container.
- Protect from light and moisture.
What should I do in case of emergency?
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.
