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Fluoxetine

Prescription

Selective serotonin reuptake inhibitor (SSRI)

Last reviewed 19 Apr 2026 · PetCare.AI Editorial Team

Species

Dog, Cat

Brands

4 available

Interactions

14 documented

Formulations

Mechanism of action

Selectively inhibits serotonin (5-HT) reuptake at presynaptic neurons, increasing serotonergic neurotransmission; used for anxiety-based behavioural disorders

At a glance

Class

Selective serotonin reuptake inhibitor (SSRI)

Schedule

Prescription

Storage

Store below 25°C, protect from light

Dosing

🐕

Dog

Separation anxiety / Compulsive disorders / Aggression (fear-based)

Dose

1–2 mg/kg

Route

Frequency

SID

Max dose

80 mg

Duration: Minimum 6–8 weeks for effect; long-term with behaviour modification

🐈

Cat

Inappropriate elimination / Intercat aggression / Compulsive grooming

Dose

0.5–1.5 mg/kg

Route

Frequency

SID

Max dose

10 mg

Duration: Minimum 8 weeks; long-term

Educational reference only

This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

Formulations

💊

Capsule — 2

Strength

10mg

Available in India

Strength

20mg

Available in India

💊

Tablet (chewable, veterinary) — 4

Strength

8mg

Strength

16mg

Strength

32mg

Strength

64mg

Storage

Store below 25°C, protect from light

Safety

Absolute contraindications — do not use

Concurrent MAO inhibitors (e.g., selegiline, amitraz)
Serotonin syndrome risk — 14-day washout
SelegilineAmitraz
Known hypersensitivity to SSRIs

Use with caution

Seizure history
May lower seizure threshold
Concurrent tramadol
Serotonin syndrome risk

Adverse effects

Common

Anorexia (first 1–2 weeks)

Lethargy

GI upset

Serious

Serotonin syndrome

Seizures

Hepatotoxicity (rare, cats)

Monitoring parameters

Behaviour assessmentAppetiteBody weightHepatic function (cats)

Educational reference only

Interactions

Contraindicated — 2

Selegiline (L-Deprenyl)

contraindicated

Risk of serotonin syndrome — MAO inhibitor + SSRI combination is absolutely contraindicated

Management: Never combine. Allow 14-day washout from selegiline and 5-week washout from fluoxetine.

Procarbazine

contraindicated

Procarbazine (MAOI activity) + SSRI: serotonin syndrome.

Management: NEVER combine. Discontinue SSRI with adequate washout before MOPP protocol.

Major — 8

Tramadol

major

Both increase serotonin; risk of serotonin syndrome (agitation, tremors, hyperthermia, seizures)

Management: Avoid concurrent use. If both needed, use lowest doses and monitor closely for serotonin syndrome signs.

Clomipramine

major

Both are serotonergic; fluoxetine inhibits CYP2D6 increasing clomipramine levels. High risk of serotonin syndrome.

Management: Do NOT use concurrently. Allow 5-week washout when switching between SSRIs and TCAs.

Linezolid

major

Linezolid (weak MAO-A inhibitor) + SSRI: serotonin syndrome risk (hyperthermia, seizures, rigidity).

Management: Avoid combination. If linezolid essential, taper SSRI before starting (fluoxetine requires 5-week washout due to long half-life metabolite).

Amitriptyline

major

Fluoxetine inhibits CYP2D6 metabolism of amitriptyline, increasing TCA levels. Both serotonergic — serotonin syndrome risk.

Management: Avoid. Allow adequate washout (5 weeks from fluoxetine).

Mirtazapine

major

Both serotonergic. Fluoxetine inhibits CYP2D6 metabolism of mirtazapine, increasing levels. Serotonin syndrome risk from combined serotonergic activity.

Management: Avoid combination. If appetite stimulation needed with SSRI, reduce mirtazapine dose and monitor for serotonin syndrome.

Codeine

major

Codeine requires CYP2D6 conversion to active morphine. Fluoxetine potently inhibits CYP2D6, blocking codeine activation and rendering it ineffective as analgesic/antitussive.

Management: Codeine will be ineffective. Use alternative opioid not requiring CYP2D6 activation (hydromorphone, morphine, fentanyl).

Dextromethorphan

major

Fluoxetine inhibits CYP2D6 (which metabolizes DXM) AND both are serotonergic (DXM: NMDA antagonist + sigma-1 agonist + weak SRI). Combined: serotonin syndrome risk and DXM accumulation.

Management: Avoid. If antitussive needed with SSRI, use non-serotonergic option (hydrocodone, butorphanol).

Imipramine

major

Fluoxetine inhibits CYP2D6 metabolism of imipramine, increasing TCA levels. Both serotonergic — serotonin syndrome risk.

Management: Avoid. Allow 5-week fluoxetine washout before imipramine.

Moderate — 4

Trazodone

moderate

Both increase serotonin via different mechanisms; additive serotonergic effects

Management: Common combination in veterinary behaviour medicine but use with caution. Start trazodone at low dose.

Alprazolam

moderate

Fluoxetine inhibits CYP3A4 metabolism of alprazolam, increasing levels and prolonging sedation.

Management: Reduce alprazolam dose by 25-50%. Monitor for excessive sedation.

Buspirone

moderate

Fluoxetine inhibits CYP3A4 metabolism of buspirone, potentially increasing buspirone levels. Both serotonergic but different mechanisms.

Management: Monitor for increased buspirone effects (dizziness, GI upset). Usually well-tolerated combination at standard doses.

Cyproheptadine

moderate

Cyproheptadine is a 5-HT2 serotonin antagonist. It directly opposes the serotonergic effects of SSRIs, potentially reducing antidepressant/behavioral efficacy. However, this property is therapeutically useful for treating serotonin syndrome.

Management: Not typically combined for behavioral indications (antagonistic). However, cyproheptadine is the TREATMENT for serotonin syndrome caused by SSRIs — keep available as rescue.

Educational reference only

Brands

International

Reconcile

Elanco

Prozac

Lilly

India

Fludac

Cadila/Zydus

Flunil

Intas

FAQs

Frequently asked questions

›What is Fluoxetine?

Fluoxetine is a selective serotonin reuptake inhibitor (ssri) used in pets. Selectively inhibits serotonin (5-HT) reuptake at presynaptic neurons, increasing serotonergic neurotransmission; used for anxiety-based behavioural disorders

›What is Fluoxetine used for in pets?

Fluoxetine is used in veterinary medicine for: Separation anxiety / Compulsive disorders / Aggression (fear-based); Inappropriate elimination / Intercat aggression / Compulsive grooming.

›What is the Fluoxetine dose for dogs?

For dogs, Fluoxetine is typically dosed as follows — Separation anxiety / Compulsive disorders / Aggression (fear-based): 1–2 mg/kg PO SID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What is the Fluoxetine dose for cats?

For cats, Fluoxetine is typically dosed as follows — Inappropriate elimination / Intercat aggression / Compulsive grooming: 0.5–1.5 mg/kg PO SID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What are the side effects of Fluoxetine?

Common: Anorexia (first 1–2 weeks), Lethargy, GI upset. Serious (call your vet immediately): Serotonin syndrome, Seizures, Hepatotoxicity (rare, cats).

›Does Fluoxetine need a prescription?

Yes. Fluoxetine is a prescription medication and should only be administered under veterinary supervision.

›When should Fluoxetine not be used?

Do not use Fluoxetine if: Concurrent MAO inhibitors (e.g., selegiline, amitraz); Known hypersensitivity to SSRIs.

Educational reference only