By Dr. Michelle Frye, DVM · Published 2026-05-01
TL;DR. Fluoxetine (Reconcile, generic Prozac) is an SSRI used in dogs and cats for separation anxiety, fear-based aggression, compulsive behavior, and feline urine marking. Takes 4–8 weeks for full effect. Daily medication. Pairs with a behavior plan; meds alone rarely fix the problem.
The Dog Who Eats the Couch When You Leave
You went to the grocery store. You came home to a couch with no upholstery, a chewed door frame, and a neighbor leaving a note about "the howling." The dog is delighted to see you. The dog is also exhausted, because being your dog when you are not there is not a happy state of being — it is a panic attack with teeth and time.
Separation anxiety is one of the most underdiagnosed and undertreated conditions in companion-animal medicine. Fluoxetine is one of our best tools for it. So let's talk about putting your dog on Prozac.
What Fluoxetine Actually Does
Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) borrowed from human psychiatry. It increases serotonin availability in the brain over time, raising the threshold at which fear and reactive behaviors take over. It is not a sedative. It will not knock your dog out. It will, slowly, change the underlying baseline.
- Dog dose: 1–2 mg/kg orally once daily.
- Cat dose: 0.5–1 mg/kg orally once daily.
- Onset: 4–8 weeks for full effect. Subtle changes may appear at 2 weeks.
- Reconcile is the FDA-approved canine brand, formulated as a flavored chewable.
Things People Are Wrong About
Myth 1: "It'll change his personality." The opposite. Patients on the right SSRI become more like themselves — the curious, playful, sleeping-through-the-night version — not less. The drug isn't masking a personality. It's removing a panic response.
Myth 2: "It works in a week." No. Plan on 4–8 weeks before judging effect. The first 2 weeks may even bring mild GI upset and lethargy that resolves.
Myth 3: "He's better, time to stop." Stopping abruptly often brings the symptoms back within weeks. Plan on 6–12 months minimum, then taper under veterinary supervision.
Myth 4: "Drugs alone will fix it." Almost never. Fluoxetine creates the headspace for behavior modification to actually work. Without a paired plan from your vet or a board-certified veterinary behaviorist, you are leaving most of the benefit on the table.
When NOT to Use Fluoxetine
Avoid combination with other serotonergic drugs (trazodone, tramadol, MAOIs, selegiline) without veterinary direction — serotonin syndrome is rare but real. Use cautiously in pets with significant liver disease or seizure history. Discontinue and call your vet if your pet becomes more agitated or aggressive after starting (a small minority do).
What I Tell Owners After 30 Years
Behavior medications carry a stigma they do not deserve. The dog who chews her own paws bloody from anxiety, the cat who pees on the laundry every time the in-laws visit, the dog who can't be left alone for ten minutes — these are medical problems with medical answers. Fluoxetine, paired with a thoughtful behavior plan, has rescued more pet-owner relationships than any single intervention I prescribe. Be patient. Give it eight weeks. Don't stop without a plan.
Frequently Asked Questions
What is fluoxetine used for in dogs?
Fluoxetine treats separation anxiety, generalized anxiety, fear-based aggression, noise phobia, and compulsive behaviors such as tail-chasing and lick granuloma. The FDA-approved brand for canine separation anxiety is Reconcile.
Can cats take fluoxetine?
Yes. Common feline indications include urine marking, inter-cat aggression, and compulsive overgrooming. The dose is lower than for dogs.
How long does fluoxetine take to work in pets?
Full clinical effect typically takes 4–8 weeks. Subtle changes may appear at 2 weeks. Do not judge the medication earlier.
What are the side effects of fluoxetine?
Reduced appetite, lethargy, and mild GI upset are most common in the first 1–2 weeks and usually resolve. Less commonly, irritability or new aggression can occur — contact your veterinarian if your pet seems worse.
Can fluoxetine be given with trazodone?
Yes, with veterinary supervision. Many anxious patients use fluoxetine for daily baseline management and trazodone situationally. Watch for serotonin-related side effects.
How long should my dog stay on fluoxetine?
Most behavior cases benefit from at least 6–12 months on the medication, paired with active behavior modification, before considering a taper.
Is fluoxetine the same as Prozac?
Yes — Prozac is the human brand of fluoxetine. Reconcile is the FDA-approved veterinary version, formulated as a chewable tablet for dogs.
Where can I buy fluoxetine for my pet?
Fluoxetine is prescription-only. Smarty Vets dispenses Reconcile, generic fluoxetine, and pharmacy-compounded liquids from a licensed pharmacy.
This article is for educational purposes and is not a substitute for veterinary advice. Always consult your veterinarian before starting, stopping, or changing any medication for your pet.