Good or bad? For the right dog, mostly good. Fluoxetine, the drug in Prozac, is FDA-approved for dogs in one form, Reconcile chewable tablets, to treat separation anxiety together with a behavior training plan. Vets also use it extra-label for other anxieties and compulsive behaviors. It isn't a sedative and it isn't fast: some dogs improve within a week or two, others need up to 8 weeks.
The "bad" part is real but manageable: side effects, rare seizures, and a few dangerous combinations, including amitraz tick collars. Your vet sets the dose. Below: a sourced dosage chart and calculator, a week-by-week timeline, side effects, what never to mix it with, and when to call.
What Fluoxetine Is and How It Works
Fluoxetine is a selective serotonin reuptake inhibitor (SSRI). Serotonin is a chemical messenger in the brain involved in mood. Nerve cells normally pull it back in soon after releasing it; fluoxetine slows that reuptake, so more serotonin stays available. In dogs the liver turns fluoxetine into norfluoxetine, which works the same way and lingers for days.
In people, SSRIs are prescribed for depression, obsessive-compulsive disorder and panic disorder (Fitzgerald and Bronstein 2013). In dogs, the label says it makes a dog more receptive to training, and although some dogs seem calmer, it does not act as a sedative. That's why it is paired with a behavior plan rather than given on its own.
What Fluoxetine Is Used For in Dogs
On the label: separation anxiety in dogs 6 months or older weighing at least 8.8 lb (4 kg), alongside a behavior modification plan. Dogs with separation anxiety may destroy things, bark or whine, soil the house, drool heavily or try to escape when left alone (see our guide to separation anxiety in dogs).
Extra-label uses (legal and common, chosen case by case by your vet), as listed by the Merck Veterinary Manual:
- other anxieties and phobias, such as fear of thunderstorms
- fear aggression and conflict aggression
- compulsive disorders, such as tail chasing, spinning or obsessive licking
- excessive arousal and impulsivity
- urine marking
Two caveats. For compulsive disorders, a trial of 63 dogs found that owners reported more improvement on fluoxetine than on placebo after 6 weeks, but their daily diaries showed no drop in the number or length of episodes, and the authors called the results equivocal (Irimajiri 2009). And aggression cuts both ways: it is an extra-label use, yet it is also a listed side effect. A dog with aggression, including the kind people often blame on dominance, needs a careful plan with your vet or a veterinary behaviorist, not a pill alone.
Fluoxetine builds up over weeks, so it won't help with a one-off scary event. For storms, fireworks or vet visits, vets may add a medicine given beforehand, such as gabapentin or trazodone, both listed by Merck for fear and anxiety.
Before prescribing, the label asks vets to examine your dog, often with blood or urine tests, and review the history and every medicine or supplement your dog gets, since behavior changes can have medical causes. VCA Animal Hospitals also advises caution in dogs with diabetes or severe liver disease and in pregnant or nursing dogs.
Is Fluoxetine FDA-Approved for Dogs?
Yes, but only one product: Reconcile (fluoxetine hydrochloride) beef-flavored chewable tablets, approved under NADA 141-272 for canine separation anxiety with a behavior modification plan (Reconcile label, DailyMed).
Everything else is extra-label: human-labeled Prozac, generic fluoxetine capsules, tablets and liquid, compounded liquids and chews (compounded fluoxetine is not FDA-approved), and any use other than separation anxiety. That's normal in veterinary medicine; it means your vet, not a label, sets the use and the dose. More in our post on unapproved animal drugs and the FDA.
Fluoxetine Dosage Chart for Dogs
For information only. These are typical published dose ranges, not a prescription and not medically verified for your pet. Your veterinarian sets the dose after examining your pet. Never start, stop or change a medicine without their OK.
Species | Use | Dose (per kg and per lb) | How often | Route | Source |
|---|---|---|---|---|---|
Dog | Separation anxiety, with a behavior plan (FDA label: Reconcile chewables) | 1 to 2 mg/kg (0.5 to 0.9 mg/lb) | once a day | by mouth, with or without food | |
Dog | Other anxieties and compulsive behaviors (extra-label, Merck) | 1 to 2 mg/kg (about 0.5 to 0.9 mg/lb) | once a day (every 24 hours) | by mouth |
Dog weight (lb) | Dog weight (kg) | Reconcile tablet | Source |
|---|---|---|---|
8.8 to 17.6 | 4.0 to 8.0 | 1 chewable tablet of 8 mg | Reconcile FDA label (DailyMed), Table 1 |
17.7 to 35.2 | 8.1 to 16.0 | 1 chewable tablet of 16 mg | Reconcile FDA label, Table 1 |
35.3 to 70.4 | 16.1 to 32.0 | 1 chewable tablet of 32 mg | Reconcile FDA label, Table 1 |
70.5 to 140.8 | 32.1 to 64.0 | 1 chewable tablet of 64 mg | Reconcile FDA label, Table 1 |
Dose calculator · Fluoxetine
Fluoxetine dose calculator for dogs
Not a prescription. For information only. These are typical published dose ranges, not a prescription and not medically verified for your pet. Your veterinarian sets the dose after examining your pet. Never start, stop or change a medicine without their OK.
Only give what your vet prescribed.
All doses in this calculator
| Pet | Use | Typical dose | How often | Route | Source |
|---|---|---|---|---|---|
| Dog | Separation anxiety, with a behavior plan (FDA label: Reconcile chewables) | 4 to 8 kg (8.82 to 17.6 lb): 1 chewable tablet of 8 mg; 8.1 to 16 kg (17.9 to 35.3 lb): 1 chewable tablet of 16 mg; 16.1 to 32 kg (35.5 to 70.5 lb): 1 chewable tablet of 32 mg; 32.1 to 64 kg (70.8 to 141.1 lb): 1 chewable tablet of 64 mgLabel dose 1 to 2 mg/kg (0.5 to 0.9 mg/lb) once a day, always with a behavior modification plan. The label covers dogs 6 months or older weighing 4 kg (8.8 lb) or more; for lighter or heavier dogs, your vet decides. Missed dose: give the next one at the usual time; never double. Not for dogs with epilepsy or a seizure history, and never with an amitraz tick collar or another MAOI. | once a day | by mouth, with or without food | Reconcile FDA label (DailyMed) |
| Dog | Other anxieties and compulsive behaviors (extra-label, Merck) | 1 to 2 mg per kg (0.45 to 0.91 mg per lb)Extra-label: your vet decides whether fluoxetine fits and at what dose. Merck lists it for anxiety disorders, phobias, fear or conflict aggression, compulsive disorders, excessive arousal and urine marking. Used with a behavior plan; may take 3 to 4 weeks to affect behavior. For compulsive disorders, a 63-dog trial at this range gave equivocal results (Irimajiri 2009, JAVMA). | once a day (every 24 hours) | by mouth | Merck Veterinary Manual |
Only give what your vet prescribed, at the dose they set.
Notes on the chart:
- Not covered by the label: dogs under 6 months, under 4 kg (8.8 lb) or over 64 kg. Your vet decides for those dogs.
- Missed dose: the label says to give the next dose at the usual time. Don't double up.
- Side effects and the dose: in the label studies, some dogs needed a lower dose for a while because of poor appetite, vomiting, shaking or low energy; about half went back to the full dose after 1-2 weeks. That call belongs to your vet.
- Too much swallowed (an extra dose, a chewed bottle, or someone's own Prozac): call your vet now, or ASPCA Animal Poison Control at (888) 426-4435 or Pet Poison Helpline at (855) 764-7661.
How Long Does Fluoxetine Take to Work?
Longer than most owners expect, and that's normal:
- Weeks 1-2: some dogs already improve. In the label's 8-week trial, 42% of dogs on fluoxetine plus training improved in the first week, versus 18% on training alone.
- Weeks 3-4: the Merck Veterinary Manual notes fluoxetine may take 3 to 4 weeks before it affects behavior.
- Week 8: by the end of the trial, 73% of dogs on fluoxetine plus training had improved significantly, versus 51% on training alone. If there's no improvement by 8 weeks, the label tells vets to rethink the plan.
Keep a simple diary of what happens when you leave (how long you were gone, any accidents or damage) so your vet has something real to judge at each check-in.
Fluoxetine Works Best With a Behavior Plan
The label is blunt about this: giving fluoxetine without a diagnosis or behavior modification may expose a dog to side effects without any lasting benefit. In the trial, medicine plus training worked faster and better than training alone.
A typical plan, as the label describes it:
- Get your dog used to your comings and goings, so your keys and coat stop being alarm bells.
- Teach sit and stay, and over time, being content while alone.
- Stop rewarding attention-seeking behavior.
- Leave for short periods, then slowly make them longer.
Your vet may refer you to a veterinary behaviorist or a qualified trainer. If barking is the main complaint, our guide on why dogs bark helps you describe what you see.
Side Effects of Fluoxetine in Dogs
Most side effects in the label studies were mild and came and went. According to the Reconcile label, you may see:
- calmer or more tired than usual
- decreased appetite, and weight loss (5% or more of body weight in about 30% of treated dogs, versus 13% on training alone)
- vomiting, diarrhea or constipation
- shaking or shivering, restlessness, panting
- whining or more vocalizing
- drooling, incoordination, disorientation or confusion
- dilated pupils, anxiety, aggression
- ear infections
Seizures are the most serious side effect. They can happen even in dogs with no seizure history, and in rare, severe cases they have been fatal. That's why fluoxetine isn't used in dogs with epilepsy or a history of seizures.
When to call:
- Mention at your next visit: mild sleepiness, a slightly smaller appetite, softer stools that settle.
- See your vet soon: not eating for a day or more, steady weight loss, repeated vomiting or diarrhea, new restlessness, anxiety or growling.
- Call now: a seizure, sudden aggression, trouble standing, or the serotonin syndrome signs below.
Never Combine Fluoxetine With These
The sources draw the line in two places.
Never, per the Reconcile label:
- MAOI drugs and products, including selegiline and amitraz, and not within 14 days after stopping one. Amitraz is the active ingredient in some impregnated tick collars for dogs (Merck Veterinary Manual), so check your dog's collar and ask before using any tick or flea product.
- Drugs that lower the seizure threshold, such as the phenothiazines acepromazine and chlorpromazine.
- Dogs with epilepsy or a seizure history, or a known allergy to fluoxetine or other SSRIs.
- For 6 weeks after stopping fluoxetine, any drug that may interact with it, because fluoxetine and norfluoxetine leave the body slowly.
Only if your vet plans it: other medicines that raise serotonin can add up to serotonin syndrome. They include tramadol, fentanyl, mirtazapine, buspirone and chlorpheniramine (Fitzgerald and Bronstein 2013), trazodone (VCA Animal Hospitals) and other antidepressants. Vets sometimes combine behavior medicines on purpose, so this isn't a "never", but it is a "never on your own". Don't give leftover tramadol or anyone's antidepressant to a dog on fluoxetine.
The label also asks for caution with drugs that affect the liver's cytochrome P450 enzymes, such as ketoconazole. The simple rule: tell your vet about everything your dog gets, including over-the-counter products, supplements, herbal remedies, and flea, tick and worm products.
Never Give Your Dog Your Own Prozac
Vets sometimes prescribe human-labeled fluoxetine for dogs, with a dose worked out for your dog. Giving your own tablets is a different thing: antidepressant ingestions are among the top accidental poisonings reported in pets, according to Pet Poison Helpline.
It works the other way too: Reconcile is labeled "not for use in humans", and anyone who swallows it should get medical attention right away.
Serotonin Syndrome and Overdose
Serotonin syndrome happens when too much serotonin builds up, from an overdose or from combining medicines that raise it. Signs usually come in a cluster (Merck Veterinary Manual; Fitzgerald and Bronstein 2013):
- agitation, nervousness, a strange or dull mental state
- muscle twitching, tremors, stiff muscles, wobbliness
- fever or overheating
- vomiting, diarrhea, dilated pupils, drooling
- fast or slow heart rate
- seizures
This is a Call now situation. Phone your vet or an emergency clinic, or ASPCA Animal Poison Control at (888) 426-4435 or Pet Poison Helpline at (855) 764-7661, and bring the medicine packaging. Don't try to make your dog vomit unless a vet tells you to. Our guide to serotonin syndrome in dogs explains what the vet does next.
With veterinary care, the outlook is excellent. In a review of 313 dogs reported to Pet Poison Helpline after swallowing SSRIs, most showed no signs at all, sleepiness was the most common sign, and every dog with complete follow-up survived (Thomas 2012).
If your dog is having a seizure, be careful not to get hurt while handling them, and get help to move them if you can. More on seizure causes in what toxins can cause seizures in dogs.
Stopping Fluoxetine
Don't stop or change it without your vet: the Reconcile label says no taper is needed, because the drug leaves the body slowly, but many vets prefer to reduce it gradually, and VCA Animal Hospitals advises against stopping it abruptly. Either way, the label recommends keeping the behavior plan going after the medicine ends so the old behaviors don't come back.
Storing Fluoxetine Safely
Per the label: room temperature, 68 to 77 °F (20 to 25 °C), with the drying packet in and the child-resistant cap closed. Keep it out of reach of children and pets: the chewables are flavored, and most dogs eat them readily. For compounded products, follow the pharmacy label and expiry date, and ask your vet or pharmacy how to dispose of leftovers.
Quick Answers
Will fluoxetine sedate my dog? No. It is not a sedative, though some dogs seem calmer or a bit tired, especially early on.
Is fluoxetine safe for dogs long-term? The label's field trial covered 8 weeks, and a laboratory safety study ran for a year at the label dose. Longer use is a decision for you and your vet, based on how the behavior plan is going.
Originally written by Helen Roberts. Updated by the I Love Veterinary editorial team.
Sources
- DailyMed: Reconcile (fluoxetine hydrochloride) chewable tablets, FDA-approved label, NADA 141-272
- Merck Veterinary Manual: Common Drugs Used to Treat Behavior Problems in Dogs
- Merck Veterinary Manual: Drugs Used to Treat Behavior Problems in Dogs
- Merck Veterinary Manual: Tranquilizers, Antidepressants, Sleep Aids, and Anticonvulsants Toxicity
- Merck Veterinary Manual: Triazapentadiene (Amitraz) Toxicosis in Animals
- Irimajiri M, et al. Randomized, controlled clinical trial of the efficacy of fluoxetine for treatment of compulsive disorders in dogs. JAVMA 2009
- Fitzgerald KT, Bronstein AC. Selective serotonin reuptake inhibitor exposure. Top Companion Anim Med 2013
- Thomas DE, et al. Retrospective evaluation of toxicosis from SSRI antidepressants: 313 dogs. J Vet Emerg Crit Care 2012
- VCA Animal Hospitals: Fluoxetine
- Pet Poison Helpline: Antidepressants
- Heartland Vet Supply: Fluoxetine compounded oral suspension for dogs
This article is for general information and is not a substitute for advice from your veterinarian.
