Fluoxetine: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Reconcile, Prozac, Fludac, Flunil

Species with doses

Dogs, Cats, Horses and Sugar gliders

General dose range

1–2 mg/kg PO q24h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Canine separation anxiety (licensed) with a behaviour-modification programme
• Compulsive/stereotypic disorders (acral lick, spinning, etc.)
• Fear- and anxiety-based aggression
• Feline anxiety, urine marking and some compulsive behaviours

Fluoxetine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Separation anxiety / compulsive / aggression: Papich 5e and Plumb’s p.545 (Reconcile label): 1–2 mg/kg PO once daily with behaviour modification; efficacy may take up to 4 weeks; continue 2 months after response, then taper. Up to 3 mg/kg daily (Landsberg). Avoid with MAOIs (amitraz, selegiline) and tramadol — serotonin syndrome.

Cats

• Anxiety / urine marking / compulsive: Papich 5e: 0.5–1 mg/kg/day PO (0.5–4 mg per cat; start ¼ tablet = 2.5 mg); urine marking 1 mg/kg, up to 1.5 mg/kg. Plumb’s p.545: aggression and generalised anxiety 0.5–1.5 mg/kg once daily; urine marking 0.5–1 mg/kg (2.5–5 mg per cat).

Horses

• Behaviour disorders: Papich 5e: horses 0.25–0.5 mg/kg PO once daily, mixed with grain.

Sugar gliders

• Self-mutilation / compulsive behaviour: Carpenter Exotic Animal Formulary 6th ed, Table 7-5 (p.501): sugar gliders 1 mg/kg PO q12h (up to 1–5 mg/kg PO q8–12h) for self-mutilation. Use the liquid form; pair with husbandry/pair-bonding correction.

Contraindications

Concurrent MAO inhibitors / selegiline (serotonin syndrome — observe washout). Other strongly serotonergic drugs at high combined load. History of seizures (lowers threshold). Known hypersensitivity. Hepatic impairment (metabolised hepatically). Not a quick fix — requires behaviour modification.

Species-specific warnings

Cats: Effective for feline anxiety/marking but monitor appetite closely (anorexia risk); use low mg/kg and expect a slow onset/washout.

Adverse effects

• Reduced appetite / weight loss, especially early (transient)
• Lethargy or, conversely, restlessness/agitation early
• GI upset
• Lowered seizure threshold (rare)
• Serotonin syndrome if combined with other serotonergic drugs

Drug interactions

• MAO inhibitors / selegiline (Anipryl): contraindicated — serotonin syndrome (observe washout both ways)
• Other serotonergic drugs (tramadol, TCAs, trazodone, ondansetron): additive serotonin-syndrome risk
• CYP inhibitor: can raise levels of co-metabolised drugs
• Drugs lowering seizure threshold: additive risk

Pregnancy and lactation

Limited veterinary data; generally avoided in pregnancy unless clearly necessary.

Monitoring

• Behavioural response over 4–8 weeks (set owner expectations)
• Appetite/weight (early anorexia) and demeanour
• Concurrent serotonergic medications
• Taper when discontinuing long-term therapy

Toxicity and overdose

Overdose causes serotonergic signs — agitation, tremor, hyperthermia, tachycardia, mydriasis, vomiting, and at high doses seizures and serotonin syndrome. A common scenario is a dog ingesting the owner's human fluoxetine. The long half-life means effects (and any serotonin syndrome) can be prolonged.

Management: Decontaminate if recent ingestion (emesis/charcoal). For serotonin syndrome: cyproheptadine (serotonin antagonist), active cooling, IV fluids, control agitation/seizures with benzodiazepines, and supportive monitoring (temperature, ECG). No specific antidote; effects can be prolonged.

Clinical pearls

• The licensed go-to for canine separation anxiety — but it is one leg of a stool: behaviour modification (and often situational anxiolytics) are essential
• Counsel owners that it takes 4–6 weeks to work and is a months-long commitment
• Avoid combining with other serotonergic drugs (selegiline, tramadol, trazodone at high doses) — serotonin syndrome
• Watch for early appetite loss in cats and dogs; it usually settles
• Taper rather than stop abruptly, and remember the long washout when switching drugs

Mechanism of action

Selectively inhibits the presynaptic serotonin (5-HT) transporter, increasing synaptic serotonin in the CNS. Over weeks this produces adaptive downstream receptor changes that reduce anxiety, impulsivity and compulsive behaviour — the delay reflecting the time needed for these neuroadaptations rather than the immediate reuptake block. The long-lived active metabolite norfluoxetine sustains the effect.

Formulations and products

• 8 / 16 / 32 / 64 mg chewable (Reconcile, dogs)
• 10 / 20 mg capsule (human)
• Oral solution 4 mg/mL (20 mg/5 mL)
• Reconcile (Elanco) — 8 / 16 / 32 / 64 mg chewable, Chewable tablet
• Fludac — 10 / 20 mg capsule, Capsule (human-label)
• Flunil — 10 / 20 mg capsule; 20 mg/5 mL syrup, Capsule / syrup (human-label)

Storage

Chewables/capsules/solution: 15–30 °C, dry, protect from light.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other hormones, emergency drugs, supplements and other drugs

• Ferrous Sulfate
• Finasteride
• Fludrocortisone
• Flumazenil
• Fluticasone (Inhaled)
• Fomepizole (4-MP)
• Glipizide
• Glycopyrrolate

Frequently asked questions