Cerenia (maropitant citrate) is one of the most widely prescribed anti-nausea medications in veterinary medicine, and most dogs tolerate it well. The most commonly reported side effects are drowsiness, drooling, and diarrhea, with each affecting roughly 4% to 8% of treated dogs in clinical trials. More serious reactions like seizures or allergic collapse are extremely rare, occurring in fewer than 1 in 10,000 dogs.
How Cerenia Works
Cerenia blocks a chemical messenger called substance P from attaching to receptors in the brain’s vomiting center. This makes it effective against both nausea triggered by the stomach (like motion sickness) and nausea triggered by the brain itself (like the kind caused by kidney disease or chemotherapy drugs). It’s available as an oral tablet and as an injectable solution given at the vet’s office.
Common Side Effects
In FDA clinical trials involving hundreds of dogs, the side effects that showed up most often were mild and temporary. During a European motion sickness study, about 8% of dogs treated with Cerenia showed drowsiness, lethargy, or apathy, compared to just 1% of dogs given a placebo. Hypersalivation appeared in about 5% of treated dogs versus 2% on placebo. In a separate U.S. motion sickness trial, salivation rates were similar between treated dogs and placebo dogs (6.8% versus 5.3%), suggesting some drooling may simply be from the car ride itself.
Diarrhea was noted in about 3.9% of dogs receiving Cerenia for acute vomiting, which was actually lower than the 8.7% seen in the placebo group. This makes sense: dogs sick enough to need an anti-vomiting medication often have digestive upset already. Lethargy in that same trial was uncommon, affecting less than 1% of treated dogs.
In practical terms, if your dog seems a little sleepy or drools more than usual after taking Cerenia, that’s the most likely explanation, and it typically resolves on its own.
Pain at the Injection Site
If your dog receives the injectable form of Cerenia, there’s a good chance they’ll react to the shot itself. Transient pain and vocalization during subcutaneous injection occur frequently. In one study of 32 beagle dogs, vocalization happened in a significant number of injections, and many dogs scratched at the injection site afterward.
Refrigerating the solution before injection helps reduce the sting. Many veterinary clinics store Cerenia in the fridge for this reason. The discomfort is brief and not a sign of an allergic reaction or anything dangerous.
Rare but Serious Reactions
Serious side effects from Cerenia are documented but very uncommon. The European product labeling categorizes these as affecting fewer than 1 in 10,000 treated animals:
- Neurological signs: ataxia (loss of coordination), convulsions, seizures, or muscle tremors
- Anaphylactic-type reactions: allergic swelling, hives, skin redness, collapse, difficulty breathing, or pale gums
These reactions can happen with virtually any medication, but if your dog shows signs of a severe allergic reaction, like facial swelling, sudden weakness, or trouble breathing, that warrants immediate veterinary attention.
Safety in Puppies
Cerenia has age-specific restrictions. The injectable form can be used in puppies as young as 8 weeks, while tablets are approved for dogs 4 months and older (for acute vomiting) or 8 weeks and older (for motion sickness, depending on label).
The age cutoffs exist for a real biological reason. In puppies younger than 11 weeks, studies found histological evidence of bone marrow changes, where the bone marrow showed reduced cell production at higher frequency and severity compared to untreated puppies. This effect was not seen in puppies 16 weeks and older. Your vet will factor in your puppy’s age when deciding whether Cerenia is appropriate.
Dogs With Liver Disease
Cerenia is processed through the liver, so dogs with existing liver problems may need a dose adjustment. If your dog has been diagnosed with any form of liver disease, make sure your vet knows before starting this medication. The drug isn’t necessarily off-limits, but it may need to be given at a lower dose or monitored more carefully.
Pregnant and Breeding Dogs
The safety of Cerenia has not been evaluated in dogs used for breeding or in pregnant or lactating females. This doesn’t mean it’s known to cause harm in these situations, only that there isn’t enough data to confirm it’s safe. Most vets will avoid using it in pregnant dogs unless the benefit clearly outweighs the unknown risk.
What Happens With an Overdose
Cerenia has a relatively wide margin of safety. In studies, dogs tolerated doses up to 10 mg/kg daily for 15 days without problems. The standard therapeutic dose is 2 mg/kg for tablets, so that’s roughly five times the normal dose before issues emerge. At doses exceeding 20 mg/kg (ten times normal), dogs showed vomiting on the first dose, excessive salivation, and watery stool. Accidental double-dosing is unlikely to cause serious harm, but contact your vet or an animal poison control line if your dog gets into the medication bottle.
How Long Side Effects Last
Most side effects from Cerenia are short-lived. Drowsiness and drooling typically fade within hours of dosing. Injection site discomfort resolves within minutes. Because the medication is given once daily (for up to 5 consecutive days with the injectable form), any mild side effects tend to clear well before the next dose. If your dog’s lethargy or digestive changes persist beyond 24 hours after the last dose, it’s worth checking whether the underlying condition, rather than the medication, is responsible.