Fluoxetine for Dogs

While FDA-approved for separation anxiety, fluoxetine is also a medication for aggressive dogs.


Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) that is FDA-approved for treating separation anxiety in dogs. It is also sometimes prescribed for aggressive dogs, general anxiety, and compulsive disorders in dogs.

Fluoxetine is commonly known under its brand names Reconcile (chewable veterinary tablet), Prozac, and Sarafem.

Medication for Aggressive Dogs

If you’re looking for medication for an aggressive dog, fluoxetine is a strong choice. Be advised, however, that aggression in dogs is extremely difficult to treat successfully, even with the help of medication and compliance with a professionally guided behavior-modification program from a fear-free trainer.

Aggression in dogs as a behavior issue always carries a guarded prognosis. Even with improvement, these dogs can still be dangerous and should always be carefully managed with the safety of both humans and other dogs in mind.

Fluoxetine for Dogs Dosage

The FDA-approved fluoxetine dosage for dogs is 1 to 2 mg/kg by mouth once a day. With safe rounding, this translates to 5 to 10 mg for a 10-lb. dog, 20 to 40 mg for a 50-lb. dog, and 40 to 80 mg for a 90-lb. dog. Your veterinarian usually will start low, even as low as 0.5 mg/kg once a day, for the first couple of weeks to minimize side effects and allow your dog to acclimate to the medication. The dose is ramped up from there, as needed.

Fluoxetine for Dogs Side Effects

Reported fluoxetine side effects in dogs include:

  • Lethargy
  • Vomiting
  • Diarrhea
  • Lack of appetite

Observed possible side effects include:

  • Seizures (cause and effect is not proven)
  • Unusual aggressive behavior
  • Restlessness
  • Shaking
  • Panting
  • Confusion
  • Vocalizing
  • Drooling

If your dog exhibits any of these side effects, contact your veterinarian. Sometimes starting with a lower dose resolves the issue, with subsequent higher dosages better tolerated. Fluoxetine can be given with or without food, so if your dog vomits or stops eating after trying it one way, you may be advised to try it the other way. See also “Anti-Anxiety Medications for Dogs.”


  1. As a board member of a rescue for small dogs, we’ve found that 2.5 mg to 4 mg is most frequently the very best dose for our little ones who are generally around 10 lbs. We deal with vets around the country and find that often they are not explaining that this medication takes 6 to 8 weeks to work, and that in the first few weeks it may seem that the medication is making your dog more anxious. Having this information makes it much more likely that the dog will stay on the med long enough to see whether it is successful.

  2. My medium sized mixed breed 3-year old has been taking this for about 4 months for anxiety. At first we saw a small amount of improvement, but after 3 months she is beginning to do a lot better. Yesterday, she was shaking her head, because her ears were bothering her, so I got the wipes out to clean them. She sat down in front of me and remained still and calm while I wiped out both ears. The last time I did this, she squatted down in fear and urinated on the floor while I tried to clean them. I have also been able to do some light training with her. I know she will never be that perfect dog that will walk obediently by me off leash, but she is becoming more trustful in her small world she lives in. I hope her vet can see the difference on her next visit.

  3. One of the side effects of Fluoxetine is pruritis. Our highly reactive border collie was put on this medication and over several weeks lost nearly all her beautiful thick hair. She scratched herself nearly raw and was almost balk. Think carefully about using this medication. Having taken her off, her hair has gradually started to grow back