Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) widely used in veterinary behavioral medicine for dogs and cats. The veterinary-labeled version, Reconcile (manufactured by Elanco), is FDA-approved specifically for the treatment of canine separation anxiety when used in conjunction with a behavior modification program. Generic fluoxetine (originally marketed for humans as Prozac) is commonly prescribed at a significantly lower cost. Fluoxetine is one of only two medications FDA-approved for canine separation anxiety (the other being clomipramine/Clomicalm), and it is also used extensively off-label for various behavioral conditions in both dogs and cats.
What Is Fluoxetine Used For?
Fluoxetine is prescribed for a range of behavioral conditions:
- Separation anxiety in dogs — FDA-approved indication (Reconcile), used alongside a behavior modification program
- Compulsive disorders — tail chasing, excessive licking (acral lick dermatitis/lick granulomas), shadow chasing, fly-snapping
- Aggression — fear-based aggression, inter-dog aggression, and certain forms of territorial aggression
- Urine spraying/marking in cats — a common off-label use
- Generalized anxiety — in both dogs and cats
- Storm and noise phobias — as a daily maintenance medication (not effective for acute episodes alone)
- Feline psychogenic alopecia — over-grooming related to stress
Fluoxetine is not a quick fix — it requires 4-6 weeks of daily administration to reach full therapeutic effect. It must be combined with behavioral modification for optimal results, especially for separation anxiety.
How Does Fluoxetine Work?
Fluoxetine selectively blocks the reuptake of serotonin (5-HT) at the presynaptic neuron, increasing the amount of serotonin available in the synaptic cleft. Serotonin is a neurotransmitter involved in mood regulation, anxiety, and impulse control. By increasing serotonin availability, fluoxetine helps reduce anxiety, impulsivity, and compulsive behaviors over time.
The delayed onset of action (4-6 weeks) occurs because the brain’s serotonin system needs time to adapt to the increased serotonin levels. During this adjustment period, some animals may temporarily experience increased anxiety or behavioral changes before improvement is seen.
Dosage
Your veterinarian will determine the exact dose for your pet.
Dogs
| Dog’s Weight | Typical Dose Range | Frequency |
|---|---|---|
| 10 lbs (4.5 kg) | 5 mg | Once daily |
| 20 lbs (9 kg) | 10 mg | Once daily |
| 40 lbs (18 kg) | 10-20 mg | Once daily |
| 60 lbs (27 kg) | 20 mg | Once daily |
| 80 lbs (36 kg) | 20-40 mg | Once daily |
| 100+ lbs (45+ kg) | 40 mg | Once daily |
Standard canine dose: 1-2 mg/kg once daily.
Cats
| Cat’s Weight | Typical Dose Range | Frequency |
|---|---|---|
| 6-8 lbs (2.7-3.6 kg) | 2.5-5 mg | Once daily |
| 8-12 lbs (3.6-5.4 kg) | 5 mg | Once daily |
| 12+ lbs (5.4+ kg) | 5-10 mg | Once daily |
Standard feline dose: 0.5-1.5 mg/kg once daily.
How to Give Fluoxetine to Your Dog or Cat
- Reconcile (veterinary): Flavored chewable tablets designed for dogs. Available in multiple strengths.
- Generic fluoxetine: Tablets (10 mg, 20 mg) and capsules (10 mg, 20 mg, 40 mg). Liquid formulation (20 mg/5 mL) also available.
- Can be given with or without food.
- Once daily dosing — give at the same time each day.
- Do not stop abruptly. Taper gradually over 2-4 weeks under veterinary guidance to avoid withdrawal effects.
- Allow 4-6 weeks to assess effectiveness. Do not increase the dose or discontinue prematurely.
- If you miss a dose, give it as soon as you remember. If it is close to the next dose, skip and resume the normal schedule.
Side Effects
| Common Side Effects | Serious Side Effects (Contact Your Vet) |
|---|---|
| Decreased appetite (most common) | Seizures |
| Mild lethargy or drowsiness | Tremors or agitation |
| GI upset (vomiting, diarrhea) | Severe or persistent anorexia |
| Restlessness (initially) | Signs of serotonin syndrome (panting, high heart rate, tremors, high body temperature, dilated pupils) |
| Increased anxiety (first 1-2 weeks, then usually improves) | Difficulty urinating |
Most side effects are mild and temporary, resolving within the first 1-2 weeks as the pet adjusts to the medication. Decreased appetite is the most commonly reported effect in both dogs and cats.
Drug Interactions
- MAO inhibitors (selegiline/Anipryl, amitraz): NEVER combine. Risk of fatal serotonin syndrome. Wait at least 2 weeks between stopping an MAOI and starting fluoxetine, and at least 5 weeks between stopping fluoxetine and starting an MAOI.
- Tramadol: Risk of serotonin syndrome when combined with SSRIs. Avoid concurrent use.
- Other serotonergic drugs (trazodone, clomipramine, buspirone): Increased serotonin syndrome risk. Some combinations are used by veterinary behaviorists with careful monitoring, but should not be attempted without professional guidance.
- Cyproheptadine: Used as a serotonin antagonist and can be used to treat serotonin syndrome.
- Phenobarbital and other CYP450 inducers: May alter fluoxetine metabolism.
- NSAIDs, anticoagulants: Fluoxetine may increase bleeding risk.
Contraindications
- Known hypersensitivity to fluoxetine
- Concurrent use with MAO inhibitors (including selegiline and amitraz-containing products like certain tick collars)
- Pregnant or lactating animals — safety not established
- Use with caution in animals with epilepsy (may lower seizure threshold)
- Use with caution in animals with diabetes (may alter insulin sensitivity)
- Use with caution in animals with liver or kidney disease
Storage
- Store at controlled room temperature, 68-77degF (20-25degC).
- Protect from light and moisture.
- Keep in original container.
- Keep out of reach of children and pets.
Cost & Availability
Fluoxetine is available as both a veterinary brand (Reconcile) and a widely available generic.
- Generic fluoxetine: $15-$30 per month — significantly less expensive than the brand-name veterinary product
- Reconcile (brand): $60-$120 per month depending on dog size
- Available forms: Tablets (10 mg, 20 mg), capsules (10 mg, 20 mg, 40 mg), liquid (20 mg/5 mL), and flavored chewable (Reconcile)
- Generic can be filled at human pharmacies with a veterinary prescription
Frequently Asked Questions
How long does fluoxetine take to work? Most pets require 4-6 weeks of daily dosing before significant behavioral improvement is seen. Some dogs show initial improvement within 1-2 weeks, but the full therapeutic effect takes longer. Do not judge effectiveness based on the first few weeks.
Does fluoxetine need to be combined with behavioral training? Yes. The FDA approval for Reconcile specifically requires its use in conjunction with a behavior modification program. Medication alone is less effective than medication plus behavioral modification. Your veterinarian or a veterinary behaviorist can help design an appropriate behavior plan.
What is the difference between Reconcile and generic fluoxetine? The active ingredient is identical. Reconcile is a flavored chewable tablet designed specifically for dogs, while generic fluoxetine comes in standard tablets and capsules. Many veterinarians prescribe the generic version due to its significantly lower cost.
Can fluoxetine be used for cats? Yes, fluoxetine is commonly used off-label in cats for urine spraying/marking, compulsive grooming, inter-cat aggression, and generalized anxiety. It can be very effective for feline behavioral issues.
What happens if I stop fluoxetine suddenly? Abrupt discontinuation can cause withdrawal effects including increased anxiety, irritability, GI upset, and behavioral changes. Always taper fluoxetine gradually over 2-4 weeks under veterinary guidance.
Sources & References
- FDA - Reconcile (Fluoxetine) Approval
- DailyMed - Reconcile Label
- Merck Veterinary Manual - Behavioral Pharmacotherapy
- VCA Hospitals - Fluoxetine
- AVSAB - Position Statement on Behavioral Medications
Verification Notes
The FDA approval of Reconcile (fluoxetine) for canine separation anxiety is confirmed as TRUE in the fact-check report (Claim C8). The requirement for combination with a behavior modification program is verified from the DailyMed label and FDA approval (Claim C9). Pricing for generic fluoxetine ($15-30/month) versus Reconcile ($60-120/month) is consistent with the research corpus. The 4-6 week onset period and serotonin syndrome warnings are well-documented in veterinary pharmacology references.