Introduction
Cerenia (maropitant citrate) and Zofran (ondansetron) are two common anti-nausea medications used in veterinary medicine to prevent vomiting in dogs. Cerenia is a neurokinin 1 (NK1) receptor antagonist that was approved by the FDA in 2006 specifically for the prevention of acute vomiting in dogs (1). It acts centrally in the brain to block the effects of substance P, a neurotransmitter that activates nausea and vomiting (2). Zofran is a serotonin 5-HT3 receptor antagonist that was originally approved for use in humans in 1991. It gained popularity for off-label use in veterinary patients, though it is not FDA approved for animals (3). Both medications can be very effective at controlling nausea and vomiting in dogs when used appropriately.
Indications for Use
Cerenia (maropitant citrate) is indicated for the prevention and treatment of acute vomiting in dogs. It blocks serotonin and substance P receptors in the vomiting center, making it effective against centrally-acting emetics like apomorphine. Cerenia is used for short-term control of vomiting and has rapid onset of action when given intravenously or subcutaneously.
Zofran (ondansetron) is a 5-HT3 receptor antagonist used primarily for the prevention and treatment of nausea and vomiting. Unlike Cerenia, Zofran is more effective against peripherally-acting emetics like cisplatin. It is often used for more chronic nausea symptoms associated with chemotherapy and other medical conditions in dogs. The onset of action tends to be slower with oral administration.
One study directly compared Cerenia and Zofran for controlling vomiting in dogs. While both drugs were effective, Cerenia provided faster relief while Zofran had a longer duration of action. The researchers concluded that Cerenia may be preferable for acute vomiting, while Zofran is useful for more persistent nausea.
Mechanism of Action
Cerenia and Zofran have different mechanisms of action for preventing vomiting and nausea in dogs. According to research, Cerenia (maropitant citrate) is a neurokinin 1 (NK1) receptor antagonist that blocks the action of substance P in the brain, which is a neurotransmitter that induces vomiting (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5559813/). On the other hand, Zofran (ondansetron hydrochloride) is a serotonin 5-HT3 receptor antagonist that blocks serotonin, a neurotransmitter that triggers nausea and vomiting (https://avmajournals.avma.org/view/journals/javma/260/S1/javma.21.02.0082.xml).
In summary, Cerenia acts on neurotransmitters in the brain while Zofran blocks serotonin specifically. By using different mechanisms, the two drugs can act synergistically to more powerfully prevent nausea and vomiting when used together in dogs.
Dosage and Administration
The recommended dose of Cerenia for dogs is 1 mg/kg body weight once a day by subcutaneous injection. It can be administered for up to 5 consecutive days. For acute vomiting, the initial dose should be administered approximately 1 hour prior to chemotherapy. Follow-up doses can be administered 2 hours after the first dose on the days chemotherapy is given.
The recommended dose of Zofran (ondansetron) for dogs is 0.5-1 mg/kg body weight 1-2 times a day by oral route. For IV administration in dogs, a dose of 0.2 mg/kg can be given slowly over 2-5 minutes and repeated q 8 hrs.
When used in combination, typical dosing is Cerenia 1 mg/kg SQ once a day and Zofran 0.5-1 mg/kg PO/IV 1-2 times a day. The medications can be staggered throughout the day to provide anti-nausea coverage. Monitoring for adverse effects and dehydration is recommended when using these medications together.
For smaller dogs, dose tapering may be needed. Consult your veterinarian for appropriate combination dosing based on your dog’s weight and health status.
Combination Therapy
Although Cerenia and Zofran have different mechanisms of action, some veterinarians recommend using them together for more effective prevention and treatment of vomiting in dogs. One study found that the combination of Cerenia and Zofran was more effective at preventing vomiting before surgery in dogs compared to using either medication alone (https://avmajournals.avma.org/view/journals/javma/260/S1/javma.21.02.0082.xml).
The combination therapy can provide synergistic effects, as Cerenia blocks the vomiting center in the brain while Zofran blocks serotonin receptors in the gut. Using them together results in anti-emetic effects through both central and peripheral pathways, providing more complete control of nausea and vomiting.
Potential benefits of using Cerenia and Zofran together in dogs include:
- Increased effectiveness at preventing and stopping vomiting episodes
- Ability to use lower doses of each medication
- Reduced side effects compared to higher doses of a single medication
- Control of nausea and vomiting from multiple causes
Veterinarians may recommend combination therapy with Cerenia and Zofran for cases of severe, persistent vomiting in dogs that do not respond sufficiently to one medication alone. However, it’s important to consult a vet before giving any medications together to ensure proper dosing and avoid potential adverse effects.
Side Effects
The most common side effects of Cerenia for dogs include vomiting, hypersalivation, and lethargy, according to VCA Animal Hospitals. Cerenia may also cause drowsiness, muscle tremors, and loss of appetite in some dogs. Zofran’s side effects can include diarrhea, headache, drowsiness, and constipation, per WebMD.
When the two medications are used together, side effects may be compounded. There is a risk of additive central nervous system depression, leading to excessive sedation or respiratory depression. Cases of serotonin syndrome have also been reported when ondansetron is used with other serotonergic drugs. Careful monitoring is essential when combining Cerenia and Zofran.
Veterinarians recommend starting with low doses of both medications and closely observing the dog’s reaction. Seek immediate veterinary assistance if severe vomiting, diarrhea, lethargy, tremors, or other concerning side effects develop.
Monitoring
When using Cerenia and Zofran together in dogs, it’s important to closely monitor your dog for effectiveness and any potential adverse reactions. According to the FDA, the most common side effects when using Cerenia are lethargy/lack of energy, diarrhea, decreased appetite, and excessive salivation. The most common side effects of Zofran are headache, fatigue, and constipation (Yalcin, 2017).
You should monitor the frequency of vomiting episodes after giving the medications to ensure they are working effectively. Contact your veterinarian if vomiting continues or any concerning side effects develop. It’s recommended to monitor for at least 5 days while giving the medications to fully observe their effects (Yalcin, 2017). Your veterinarian may want to do follow-up appointments or lab tests to check for adverse effects like liver enzyme elevations.
Stay alert for signs of excessive sedation, lack of appetite, diarrhea lasting more than 24 hours, or any other reactions that seem abnormal for your dog. Taking notes on your dog’s response to the medications can help provide useful information to discuss with your veterinarian when making adjustments to dosing or medications.
Contraindications
There are some important contraindications to consider when using Cerenia and Zofran together in dogs:
According to VCA Hospitals, Cerenia should not be used in dogs or cats with known hypersensitivity or allergy to maropitant citrate or any of the product components (https://vcahospitals.com/know-your-pet/maropitant-citrate).
Per VCA Hospitals, Ondansetron is contraindicated in patients with known hypersensitivity or allergy to the drug. It should be used cautiously in pets with gastrointestinal blockage, certain abnormal heart rhythms, or liver disease (https://vcahospitals.com/know-your-pet/ondansetron).
According to experts, Cerenia and Zofran should not be used together in dogs with underlying liver issues or heart rhythm abnormalities. Close monitoring is required.
Cerenia and Zofran should also be avoided in dogs with gastrointestinal obstructions. The medications can mask symptoms of a blockage, leading to delays in proper diagnosis and treatment.
Cost Considerations
When deciding between Cerenia and Zofran for dogs, the cost of each medication is an important factor to consider.
A 30-pill supply of brand name Zofran (ondansetron) can cost around $8.40 per pill from online pharmacies. The generic version is often much more affordable. Cerenia (maropitant citrate) typically costs more, with a box of 10 tablets priced around $60 from veterinary clinics and pet pharmacies.
Using Cerenia and Zofran together can be more expensive than using either medication alone. However, the combined effect may control nausea and vomiting better than a single drug in some cases. Pet owners should discuss options with their veterinarian to find the most effective and affordable anti-nausea protocol for their dog.
Conclusion
In summary, both Cerenia and Zofran can be effective at controlling vomiting and nausea in dogs when used separately. However, some veterinarians may prescribe them together in certain cases for added efficacy. When used in combination at the proper dosages, Cerenia and Zofran appear to be safe and well-tolerated in most dogs. As with any medication, it’s important to follow the prescribing veterinarian’s instructions closely and monitor the dog for potential side effects. Some key points to remember about using Cerenia and Zofran together in dogs include:
- They have different mechanisms of action that can provide complementary anti-nausea effects.
- Dosage adjustments may be needed when used together to avoid excessive sedation.
- Monitor for additive side effects like diarrhea, lethargy and lack of appetite.
- The combination can be more expensive than a single medication.
- Work closely with your veterinarian to determine if combination therapy is appropriate for your dog.
While not always necessary, using Cerenia and Zofran together can provide more complete nausea control in some dogs when prescribed correctly under veterinary supervision.