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PetDosageChart

Prozac (Fluoxetine) Dosage for Cats

Selective serotonin reuptake inhibitor (SSRI) ⏱ Onset: 4-8 weeks for full behavioral effect ⏳ Duration: 24 hours per dose

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Dosage Calculator

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Prozac Dosage Chart for Cats by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
3 lbs (1.4 kg) 0.5mg 1mg 1.5mg once daily
4 lbs (1.8 kg) 1mg 1.5mg 2mg once daily
5 lbs (2.3 kg) 1mg 1.5mg 2.5mg once daily
6 lbs (2.7 kg) 1.5mg 2mg 2.5mg once daily
7 lbs (3.2 kg) 1.5mg 2.5mg 3mg once daily
8 lbs (3.6 kg) 2mg 2.5mg 3.5mg once daily
9 lbs (4.1 kg) 2mg 3mg 4mg once daily
10 lbs (4.5 kg) 2.5mg 3.5mg 4.5mg once daily
12 lbs (5.4 kg) 2.5mg 4mg 5.5mg once daily
14 lbs (6.3 kg) 3mg 4.5mg 6.5mg once daily
16 lbs (7.3 kg) 3.5mg 5.5mg 7.5mg (10mg tablet) once daily
18 lbs (8.2 kg) 4mg 6mg 8mg (10mg tablet) once daily
20 lbs (9.1 kg) 4.5mg 7mg 9mg (10mg tablet) once daily
25 lbs (11.3 kg) 5.5mg 8.5mg (10mg tablet) 11.5mg (10mg tablet) once daily

What is Prozac (Fluoxetine) used for in cats?

urine spraying inappropriate urination anxiety compulsive overgrooming inter-cat aggression

How to give Prozac to your cat

Fluoxetine tablets are small and can be given directly or hidden in a pill pocket or small amount of wet food. A typical cat dose is 2.5-5 mg (quarter to half of a 10 mg tablet). Give at the same time each day for consistent blood levels. Do not abruptly stop — taper off gradually under veterinary guidance. Behavioral improvement takes 4-8 weeks, so do not discontinue early thinking it is not working.

Available Forms

tablet, capsule, liquid

Give with Food?

Yes — give with food

Side effects of Prozac in cats

Common side effects

decreased appetite
sedation
urinary retention
mild GI upset

Serious side effects

  • serotonin syndrome (tremors, agitation, rapid heart rate)
  • severe appetite loss
  • liver toxicity
  • seizures

When to call the vet

Call your vet immediately if your cat shows any of these signs:

  • Tremors, twitching, or agitation (serotonin syndrome)
  • Complete refusal to eat for more than 48 hours
  • Yellowing of gums or skin (liver toxicity)
  • Seizures or sudden collapse
  • Worsening behavioral issues or new aggression

Frequently Asked Questions

Does Prozac really work for cat spraying?
Yes, fluoxetine is one of the most effective medications for reducing urine spraying in cats, with studies showing a 90%+ reduction in spraying frequency in many cats. However, it should be combined with behavioral modification and environmental enrichment. It works by reducing anxiety and stress-related marking behavior.
How long does fluoxetine take to work in cats?
Fluoxetine typically takes 4-8 weeks to reach full effect in cats. Some improvement may be seen in 2-3 weeks, but do not judge effectiveness until at least 6-8 weeks of consistent daily dosing. If discontinued too early, the problem behavior often returns.
Can my cat take fluoxetine long term?
Yes, many cats take fluoxetine for months to years, sometimes for life. It is generally well tolerated long-term. Your vet may recommend periodic blood work to monitor liver function. Some cats can eventually be weaned off if the underlying behavioral triggers are resolved.
What happens if I suddenly stop giving my cat fluoxetine?
Abruptly stopping fluoxetine can cause withdrawal symptoms including irritability, GI upset, and a return of the original behavioral problem. Always taper the dose gradually over 2-4 weeks under veterinary guidance when discontinuing.
Can I use human fluoxetine for my cat?
Human fluoxetine tablets can be used for cats with veterinary guidance, but the dose must be carefully adjusted — cats typically need only 2.5-5 mg daily (a quarter to half of the smallest human 10 mg tablet). Never give a full human dose. Your vet or a compounding pharmacy can provide an appropriate formulation.