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Why is my dog suddenly lethargic and not eating on anxiety meds?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Male | neutered | 6 years and 11 months old

My dog is a Bichon Shitzu mix and is 7 years old. He has bad anxiety from thunderstorms and will shake. One time we left him in his cage on the 4th of July while we were away and came back to him chewing at his metal cage and needing dental surgery. For months he has had 1 pill of 10 mg of Fluoxetine every day and during storms he has 1-2 pills of Trazodone Hydrochoride. Recently (within the last month) he sleeps all day, doesn't have much food and isn't nearly as excited or happy. Whats wrong?

2 Answers

Most Helpful Answer

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Answered By Mirissa Duncil, DVM

Veterinarian

Published on July 11th, 2017

Hi there. I would be concerned with Hershey developing serotonin syndrome with concurrent use of trazadone and fluoxetine especially if you are giving them together often. It has to do with how the drugs are metabolized in the body and what receptors they work on. Side effects can be as you have listed, as with diarrhea, labored fast breathing, etc. I would try calling your doctor to discuss changing the dosages or weaning off the trazadone altogether. Hope this helps!

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    Answered By Megan, DVM, CVA

    Veterinarian

    Published on

    My concern is that something else may be going on besides the anxiety. If his dose of medicine hasn't changed then I wouldn't think it would be the medicine that would be causing him to be so lethargic. I would be worried that he may have something more serious going on like an infection, kidney dosesse, liver disease, heart problems, painful back/neck, or something else. I would have your vet do an exam. Your vet will be able to do a fecal, blood work and potential X-rays if needed. I hope this helps and he starts to feel better.

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