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How long until dog Prozac helps my anxious, aggressive dog?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Medium (23 - 60lb) | Male | neutered | 9 months and 4 days old | 26 lbs

How long does it take for Prozac 20mg to kick in the dogs system . Does it show signs of less anxiety fast ? How long does the effects of Prozac last in dogs ? We’ve stopped trazadone and started Prozac because of our Bongos behavioural issues . He’s in too much stress and anxiety and now tries to show moderate Aggression . . Doesn’t walk properly , shows extreme hyperactivity and doesn’t listen to commands properly . All of a sudden he was changed. He’s now leashed at his own sleeping spot.

3 Answers

Most Helpful Answer

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Answered By Juliana, DVM

Veterinarian

Published on March 18th, 2018

I am sorry to hear what you and bongo are going through. Prozac usually takes up to 3-4 weeks to start working. Some people feel they notice benefit as early as 1-2 weeks. Many times dogs with extreme anxiety need multiple medications while waiting for the Prozac to reach peak affect ( ie using trazadone or alprazolam and Prozac together). Also working with a behaviorist in conjunction with medications is very important (especially with such a young dog) and will give you the most benefit.

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Other Answers

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    Answered By Ana M, DVM

    Veterinarian

    Published on March 27th, 2018

    Thank you for submitting your question regarding Bongo. I'm sorry to hear he is having these issues. Fluoxetine can take some time to be effective. Most owners will report a response in their pet within 4-6 weeks. I recommend waiting 8 weeks before stopping and deciding this particular medication did not help. Continue with his training and behavioral modifications this will make the medication more effective in the long run. I hope this information helps. Good luck!

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    Answered By Jennifer Summerfield, DVM CPDT-KA

    Veterinarian, Certified Dog Trainer

    Published on June 25th, 2018

    Hi there. Prozac can be somewhat helpful as a background medication for some dogs with separation anxiety - but it does take up to four weeks to see an effect, and the effect is usually fairly subtle. In my experience, Prozac alone would not be expected to help much for a dog with severe separation anxiety - she really needs a situational medication to prevent the panic response, which you can give an hour or two before you leave the house and starts working right away. Common choices for this type of medication would include alprazolam, trazodone, or clonidine. I would recommend talking to your veterinarian about these other medication options, which would all be much more likely to help quickly. They are safe to be given with Prozac, so she can stay on this if needed. If your veterinarian isn't well-versed in behavior and doesn't know where to go from here, I would strongly recommend getting in touch with a veterinary behaviorist, who would be much better equipped to get her on an appropriate medication for her anxiety and will also give you a detailed training plan to work on the problem. You can search for a board-certified veterinary behaviorist in your area here: www.dacvb.org

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