Dosage Guide • FL · NY · VA • Reviewed by Dr. Tiffany Delacruz, DVM
Mirataz Dosage for a 18 lb Cat
mirtazapine · Atypical antidepressant / appetite stimulant · Large adult breed (18 lb / 8.2 kg)
What pet owners in Florida, New York, and Virginia need to know about Mirataz 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 Mirataz
Mirataz (mirtazapine transdermal ointment) is FDA-approved for cats at approximately 1.5 inches of ointment applied to the inner ear pinna once daily for up to 14 days. Oral mirtazapine is sometimes used at very low per-cat doses (1.88-3.75 mg per cat, NOT per kg) every 24-72 hours, calculated by a vet.
Cats are exquisitely sensitive to mirtazapine. The transdermal formulation eliminates many dosing errors that occur with oral mirtazapine. Over-dosing can cause severe vocalization, agitation, and serotonin syndrome — particularly dangerous in cats already on other serotonin-affecting drugs. Under-dosing fails to restart eating. Veterinary calibration is essential.
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 Mirataz is approved for
- Appetite stimulation in cats with chronic disease, chronic kidney disease, cancer, or pancreatitis
- Anti-nausea (off-label)
What to watch for in your 18 lb cat
- Increased vocalization or pacing (relatively common, often resolves)
- Severe agitation or aggression — call vet immediately, dose may be too high
- Tremors or twitching (sign of serotonin syndrome — emergency)
- Application site redness for the transdermal form
- Vomiting (uncommon)
Get a Mirataz prescription or refill in your state
RexVet is licensed in Florida, New York, and Virginia. Our veterinarians can examine your 18 lb cat by video, calculate the right Mirataz dose for their specific situation, and either fill the prescription through our in-house pharmacy or send it to a local pharmacy near you.
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Virginia
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Frequently asked questions
Frequently asked questions
How much Mirataz can I give my 18 lb cat?
Mirataz (mirtazapine transdermal ointment) is FDA-approved for cats at approximately 1.5 inches of ointment applied to the inner ear pinna once daily for up to 14 days. Oral mirtazapine is sometimes used at very low per-cat doses (1.88-3.75 mg per cat, NOT per kg) every 24-72 hours, calculated by a vet. 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 Mirataz safe for a large adult cat like mine?
Mirataz (mirtazapine) 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 Mirataz?
The most common things to watch for are: Increased vocalization or pacing (relatively common, often resolves); Severe agitation or aggression — call vet immediately, dose may be too high; Tremors or twitching (sign of serotonin syndrome — emergency). 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 Mirataz for my 18 lb cat?
Yes — if your cat is in Florida, New York, or Virginia and the medical situation is appropriate. Mirataz is one of the medications RexVet's licensed veterinarians can prescribe via a $64.99 video visit. The vet will examine your cat by video, ask about history, and either prescribe Mirataz at the right dose for your cat's weight (18 lb) or recommend a different approach if needed.
Can I get a Mirataz refill in Florida, New York, or Virginia online?
Yes. RexVet is licensed in all three states and can refill Mirataz prescriptions 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. Same-day delivery is available in most ZIP codes in FL, NY, and VA.
Mirataz 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 Mirataz dose for your 18 lb cat
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