Dosage Guide • FL · NY · VA • Reviewed by Dr. Tiffany Delacruz, DVM
Cerenia Dosage for a 18 lb Cat
maropitant · Neurokinin-1 (NK-1) receptor antagonist / antiemetic · Large adult breed (18 lb / 8.2 kg)
What pet owners in Florida, New York, and Virginia need to know about Cerenia dosing for a 18 lb (large Maine Coons-sized) cat — written by a licensed vet, no specific dose given without an exam.
The dosing principle for Cerenia
Cerenia (maropitant) for cats is typically dosed at approximately 1 mg/kg subcutaneously or orally for up to 5 consecutive days. There are FDA-approved cat tablets and injectable formulations.
Cerenia is one of the safest antiemetics available for cats, but accurate weight-based dosing matters because under-dosing fails to control vomiting (a major problem for sick cats prone to dehydration and hepatic lipidosis) while over-dosing can cause local injection-site pain. The cat formulation is different from the dog formulation — they are not interchangeable.
Why 18 lb matters
A 18 lb (8.2 kg) cat falls into the large adult category — typical examples include large Maine Coons, large Norwegian Forest Cats, and overweight Domestic Shorthairs.
Cats over 15-18 lb are often a mix of genuinely large breed (Maine Coon, Norwegian Forest) and excess body fat. Drug dosing for these cats is calculated based on LEAN body weight — not total weight. Many medications are over-dosed in overweight cats when total weight is used. A vet calculates the lean-mass-adjusted dose during the exam.
What Cerenia is approved for
- Acute vomiting
- Chemotherapy-induced nausea
- Pre-travel motion sickness
- Pre-anesthetic nausea prevention
What to watch for in your 18 lb cat
- Lethargy in the first dose or two (uncommon)
- Pain or swelling at the injection site if given SQ (a common, transient finding)
- Continued or worsening vomiting despite Cerenia — the underlying problem needs investigation
- Decreased appetite that doesn't improve once nausea is controlled
Ask about a Cerenia prescription or refill in your state
RexVet’s veterinarians are licensed in Florida, New York, and Virginia. They can examine your 18 lb cat by video and calculate the right Cerenia dose for their specific situation. If the veterinarian decides medication is appropriate, they can prescribe where state rules allow; some medications need an in-person exam first.
Florida
Online vet care for FL pet owners — Miami, Tampa, Jacksonville, Orlando, and 60+ FL cities.
New York
Online vet care for NY pet owners — NYC, Buffalo, Rochester, Syracuse, and 20+ NY cities.
Virginia
Online vet care for VA pet owners — Virginia Beach, Richmond, Norfolk, Arlington, and 20+ VA cities.
Frequently asked questions
Frequently asked questions
How much Cerenia can I give my 18 lb cat?
Cerenia (maropitant) for cats is typically dosed at approximately 1 mg/kg subcutaneously or orally for up to 5 consecutive days. There are FDA-approved cat tablets and injectable formulations. For a 18 lb (8.2 kg) cat, this gives a range that a licensed vet will narrow down based on the indication, your cat's age, kidney/liver function, and any other medications. RexVet vets serve Florida, New York, and Virginia and can calculate the right dose for your specific cat in a $64.99 video visit.
Is Cerenia safe for a large adult cat like mine?
Cerenia (maropitant) is widely used in cats in the 18 lb range, but "safe" depends on the specific cat, not just the weight. Cats over 15-18 lb are often a mix of genuinely large breed (Maine Coon, Norwegian Forest) and excess body fat. Drug dosing for these cats is calculated based on LEAN body weight — not total weight. Many medications are over-dosed in overweight cats when total weight is used. A vet calculates the lean-mass-adjusted dose during the exam. A licensed vet will check your cat's history, current medications, and any underlying conditions before prescribing.
What should I watch for after giving my 18 lb cat Cerenia?
The most common things to watch for are: Lethargy in the first dose or two (uncommon); Pain or swelling at the injection site if given SQ (a common, transient finding); Continued or worsening vomiting despite Cerenia — the underlying problem needs investigation. If you see anything concerning, contact a vet. For large adult cats specifically: Cats over 15-18 lb are often a mix of genuinely large breed (Maine Coon, Norwegian Forest) and excess body fat.
Can a RexVet online vet prescribe Cerenia for my 18 lb cat?
If the veterinarian decides it is appropriate after a video visit, they can prescribe it where state rules allow.
Can I get a Cerenia refill in Florida, New York, or Virginia online?
RexVet’s veterinarians are licensed in all three states and take Cerenia refill requests where state rules allow for cats already established on the medication. Refill visits are also $64.99. Prescriptions are filled through RexVet's in-house pharmacy (RexVetRx) or can be sent to your local pharmacy. When the veterinarian prescribes, same-day delivery is available in most ZIP codes in FL, NY, and VA.
Cerenia dosing for other cat weights
Sources
Last fact-checked: 2026-06-01. Reviewed by Dr. Tiffany Delacruz, DVM. RexVet (Rex Vets Inc.) is licensed in Florida, New York, and Virginia.
Get the right Cerenia dose for your 18 lb cat
Licensed RexVet veterinarians serving Florida, New York, and Virginia. $64.99 video visits, no membership required.