Calculate the correct Fluoxetine (Prozac) dose for your dog based on body weight.
Dosage Calculator
Enter your dog's weight to calculate the recommended dose.
Calculated Dose
Dose range (once daily)
Suggested tablet
Allow 4–6 weeks for full behavioural effect.
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⚕️ Fluoxetine is a prescription-only medication. This calculator is for reference only. Always work with a veterinary behaviourist or your vet to determine the appropriate dose and a comprehensive behaviour modification plan.
Fluoxetine (Prozac) is a selective serotonin reuptake inhibitor (SSRI) prescribed by veterinarians to treat anxiety disorders, compulsive behaviours, inter-dog aggression, and separation anxiety in dogs. It is also available as the veterinary-specific product Reconcile.
Dosage Guidelines
The standard dose of fluoxetine for dogs is 1–2 mg/kg once daily. Treatment should begin at the lower end of the range and be reviewed at 4–8 week intervals. Full behavioural effect may take 4–6 weeks to become apparent.
Available Formulations
Fluoxetine is available as 10 mg and 20 mg capsules/tablets, and as an oral solution (20 mg/5 ml). Reconcile chewable tablets come in 8 mg, 16 mg, 32 mg, and 64 mg strengths specifically for dogs.
Important Considerations
Fluoxetine should never be combined with monoamine oxidase inhibitors (MAOIs) including selegiline. It should be used alongside behaviour modification — medication alone is rarely sufficient. Side effects include reduced appetite, lethargy, and GI upset, usually resolving within 1–2 weeks.
🧠 SSRI · Serotonin Reuptake Inhibitor
Fluoxetine Dog Dosage Calculator
Evidence-based fluoxetine (Reconcile, Prozac) dosing for dogs — covering separation anxiety, compulsive disorders, fear aggression, and noise phobia, with breed-size considerations, onset timeline, and combination therapy guidance.
⚠️
Prescription medication — requires veterinary behavioural assessment. Fluoxetine is most effective when used alongside a structured behaviour modification programme, not as a standalone treatment. Takes 4–8 weeks to reach full therapeutic effect. Never combine with MAO inhibitors (selegiline/Anipryl) — risk of fatal serotonin syndrome.
Fluoxetine blocks the presynaptic serotonin transporter (SERT), increasing serotonin availability at the synapse. The active metabolite norfluoxetine has a very long half-life (> 5 days in dogs), providing sustained effects and potentially prolonged activity after discontinuation. Full behavioural effects require 4–6 weeks of consistent dosing.
Primary Uses in Dogs
Separation anxiety (only FDA-approved behaviour drug for this in dogs — Reconcile brand), generalised anxiety disorder, obsessive-compulsive disorders (excessive licking, tail chasing, fly-snapping), fear aggression, noise phobias (adjunct). Used alongside behaviour modification programmes, not as standalone treatment.
Dosing Quick Reference
Indication
Dose
Frequency
Separation anxiety
1–2 mg/kg
q24h PO
OCD/compulsive disorders
1–2 mg/kg
q24h PO
Starting dose (sensitive dogs)
0.5–1 mg/kg
q24h PO × 2 weeks, then increase
Common Side Effects
Anorexia and weight loss (weeks 1–4)
Sedation during initial adjustment period
Diarrhoea or vomiting
Serotonin syndrome if combined with MAOIs or tramadol (CONTRAINDICATED)
Paradoxical anxiety or aggression during first 1–2 weeks
Seizure threshold reduction
Monitoring
Body weight monitoring monthly (watch for significant weight loss). Behavioural assessment at 4–8 weeks for initial efficacy. Full clinical review at 3–6 months. Periodic hepatic enzymes for long-term use (fluoxetine undergoes hepatic metabolism).
⚠️ NEVER combine with selegiline (Anipryl) — this combination can cause fatal serotonin syndrome. Allow 14 days washout between selegiline and fluoxetine. Behaviour modification (training, desensitisation) is essential — fluoxetine without behaviour modification has limited efficacy. Taper slowly when discontinuing (reduce by 25% every 2 weeks).
What Is Fluoxetine for Dogs?
Fluoxetine (Reconcile — licensed veterinary chewable tablet; Prozac — human generic) is a selective serotonin reuptake inhibitor (SSRI) that blocks the serotonin transporter (SERT), increasing synaptic serotonin availability at 5-HT1A, 5-HT2A, and other receptors throughout the CNS. Reconcile is the only FDA-approved veterinary fluoxetine product specifically licensed for separation anxiety in dogs when used with a behaviour modification plan.
Fluoxetine is also used off-label for a wide range of behavioural disorders: compulsive/stereotypic behaviours (tail chasing, acral lick dermatitis, fly-biting), generalised anxiety, fear-based aggression, noise phobias, and cognitive dysfunction syndrome in senior dogs.
Pharmacokinetics in Dogs
Oral bioavailability: ~72%; food has minimal effect on absorption
Half-life: ~2 days (fluoxetine); active metabolite norfluoxetine: ~5–7 days — explains the long washout required after stopping
Onset of behavioural effect: Partial improvement often seen at 2–4 weeks; full effect requires 6–8 weeks of consistent dosing
Available forms: Reconcile 8 mg, 16 mg, 32 mg, 64 mg chewable tablets; human generic 10 mg, 20 mg, 40 mg capsules; 20 mg/5 mL oral liquid
FDA-Approved and Off-Label Indications
Separation anxiety (FDA-approved with Reconcile): Combined with behaviour modification; 1–2 mg/kg q24h
Noise phobia: Baseline therapy (add situational anxiolytic like alprazolam for acute events)
How to Use This Calculator
Enter your dog’s body weight in kg or lbs
Select the primary indication — some compulsive disorders may benefit from the higher end of the dose range
Choose whether to start at low dose (reduce side effects initially) or standard dose
Select your available tablet strength
Click Calculate for daily dose, tablet amount, and onset timeline
🧮 Fluoxetine Dose Calculator
Fluoxetine Dosing Result
Daily dose
📅 Expected Response Timeline
Frequently Asked Questions
Fluoxetine typically takes 4–8 weeks to reach full therapeutic effect in dogs. This delay is because SSRIs work through neuroplastic changes — serotonin receptor downregulation, BDNF upregulation, and hippocampal neurogenesis — that require weeks to develop, not just an increase in synaptic serotonin. Some owners notice partial improvement in impulsivity and reactivity within 2–4 weeks. Do not assess treatment failure until 8 weeks of consistent dosing have been completed. If no improvement is seen after 8–12 weeks at the maximum tolerated dose, reassess diagnosis and consider alternative medications.
Yes — combining fluoxetine (baseline SSRI) with a situational anxiolytic like alprazolam, diazepam, or trazodone is a well-established multi-modal approach in veterinary behavioural medicine. Fluoxetine provides ongoing baseline anxiety reduction while the short-acting agent is used as needed for specific triggers (thunderstorms, fireworks, vet visits). Be aware of additive serotonergic effects when combining fluoxetine with trazodone — start trazodone at a low dose and monitor for signs of serotonin syndrome (restlessness, hyperthermia, tremors, diarrhoea).
Reconcile (Eli Lilly/Elanco) is the only FDA-approved veterinary fluoxetine product, available as beef-flavoured chewable tablets in dog-appropriate sizes (8, 16, 32, 64 mg) designed to be given directly or in food. Human generic fluoxetine (Prozac) 10/20/40 mg capsules contain the same active ingredient and are equally effective at the same doses, but are off-label for dogs. Generic fluoxetine is often significantly cheaper. The clinical efficacy is equivalent; the main practical difference is palatability and tablet sizing. Always check human capsules do not contain xylitol before use.
Common side effects, especially in the first 1–2 weeks, include: decreased appetite or anorexia, vomiting or diarrhoea, lethargy or sedation, and occasionally increased anxiety or restlessness (a transient activation syndrome as serotonin levels rise before receptor adaptation occurs). Most of these resolve within 1–2 weeks. Giving with food reduces GI effects. Rare but serious side effects include serotonin syndrome (if combined with other serotonergic drugs) and disinhibition of aggression in some dogs. Long-term use is generally well-tolerated.
Because fluoxetine has a very long half-life (active metabolite norfluoxetine: 5–7 days), abrupt discontinuation causes relatively mild withdrawal effects compared to shorter-acting SSRIs. However, gradual tapering over 4–8 weeks is still recommended to prevent relapse and withdrawal symptoms. A common tapering schedule: reduce dose by 25% every 2 weeks. Behavioural improvements should be maintained by the learned conditioning from behaviour modification throughout the treatment period. Some dogs will relapse without medication and may need lifelong treatment.
Plumb DC. Plumb’s Veterinary Drug Handbook, 9th ed. Wiley-Blackwell; 2018.
Simpson BS, et al. Effects of reconcile (fluoxetine) chewable tablets plus behavior management for canine separation anxiety. Vet Ther. 2007;8(1):18-31.
Overall KL. Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier Mosby; 2013.
Landsberg G, et al. Behavior Problems of the Dog and Cat, 3rd ed. Elsevier; 2013.