Prozac(®) (fluoxetine) is a Selective Serotonin Reuptake Inhibitor (SSRI) medicine which works by inhibiting the reuptake of serotonin in the central nervous system. Serotonin is found in both the gastrointestinal tract and the brain and affects many different bodily processes, most notably mood and behavior, but also digestion and sleep. The veterinary form is known as Reconcile(®) which is manufactured by Lilly.

For correcting bad behavior:

The medicine is most effective when used in conjunction with a behavior training program. Training programs will teach your dog to stop exhibiting unwanted behaviors meaning you won’t have to keep using medicine to control the problem. We highly recommend Doggy Dan’s Online Dog Trainer which many of our clients have used with great success.

Recommended Dosage

Note: Never give products containing fluoxetine to your dog unless you have permission from your vet.

Prozac, Reconcile and other fluoxetine products (without additional active ingredients) can be given by mouth once daily at a dosage of 0.5 – 0.9 mg/lb.

Prozac dosage for canines chart

Some vets recommend 0.5 mg/lb as the upper dosage limit, while others suggest 1.35 mg/lb to be a safe maximum. Please use the dosage suggested to you by your own vet. A reduction of the dose is recommended if there is an existing liver disease or poor liver function in general.

Example: A 30 lb dog could receive between 15 mg and 27 mg of fluoxetine once daily.

How Safe Is It?

Fluoxetine, the active ingredient of Prozac and Reconcile, is safe but may not be suitable for all dogs if they are prone to:

Aggression – Though it is often used to calm down aggressive dogs and help with behavioral problems, in some cases it may cause an opposite effect where owners could see an increase in aggression. This can even occur if there are no existing behavioral problems prior to treatment.

Seizures – Dogs who are prone to seizures or epilepsy should not be given fluoxetine as the drug has been known to cause seizures. If you need a calming aid look into diphenhydramine or diazepam as alternatives.

The drug may also be unsafe when impaired liver function or diabetes mellitus is present. Practice caution and tell the vet if your dog suffers from these conditions.

Pregnancy/nursing: The drug is passed in milk and we recommend avoiding the use of fluoxetine in cases of pregnancy or nursing.

Safety Guidelines

We recommend that owners follow our safety guidelines when using this medicine:

  • Use only with veterinary approval
  • Never use alongside a MAO Inhibitor (e.g. Calming Collar)
  • Do not use alongside any other medicines unless told to do so by your vet
  • Administer a reduced dose to dogs with liver disease

Discontinue use and contact the vet immediately if serotonin syndrome or seizures occur.

What Is It Used For In Dogs?

Fluoxetine is typically used to control:

  • Aggression
  • Anxiety (including separation anxiety)
  • Repetitive behaviors

In rare cases the medicine will have the opposite effect, increasing aggression and levels of anxiety.

Side Effects

Some of the possible side effects includes:

  • Aggression
  • Anxiety
  • Diarrhea
  • Hyperactivity
  • Panting
  • Restlessness
  • Seizures
  • Vomiting

There is also a risk of serotonin syndrome when using SSRI medicines. This is a rare complication caused by a dangerous increase of serotonin activity in the CNS and can be life-threatening. This often happens when owners accidentally administer MAO Inhibitors alongside SSRIs. Watch out for common symptoms of this condition such as:

  • Anxiety
  • Diarrhea
  • Increased blood pressure
  • Increased body temperature
  • Increased heart rate
  • Restlessness
  • Rigid body
  • Shaking/tremors
  • Vomiting

If you suspect serotonin syndrome seek professional veterinary attention straight away.


Most dogs who receive overdoses of Prozac experience seizures which can be controlled by the IV administration of diazepam (Valium®). If an overdose occurs immediately get in contact with your vet or the ASPCA Pet Poison Helpline on 800-213-6680.


Dr. G. Landsberg
Lilly (Reconcile manufacturer)
Plumb’s Veterinary Drug Handbook (sixth edition)