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Dogs who suffer from anxiety may engage in unwanted behaviors like inappropriate soiling, excessive barking, or other destructive behaviors. Sometimes people will ask their veterinarian about using fluoxetine for dogs or as it’s more commonly known, Prozac, because of its effectiveness in treating anxiety and fear. When it comes to your own dog, you might be asking: What is fluoxetine used for in dogs, and how can it help my dog?

Before giving your dog any medication, it’s important to always consult with your veterinarian first. Your veterinarian can help decide if Prozac is right for your dog, and consider the side effects of fluoxetine and how it might interact with other drugs or supplements your dog is taking. Consulting with your veterinarian can help also recommend strategies for dealing with behavioral issues that are causing stress for you and your dog.

When Do Veterinarians Prescribe Fluoxetine?

Whereas Prozac is commonly prescribed as an antidepressant for people, this medication doesn’t have the same use in dogs. “We’re not diagnosing pets as having depression,” says Dr. Amy Attas, VMD of New York-based practice City Pets. “We’re diagnosing them as having some kind of disorder that leads them to have less than desirable behavior.”

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Anxiety Disorders

Some dogs, when left alone for a long period of time, may become so anxious that they start destroying household items or have housebreaking issues. Dogs with separation anxiety might engage in self-destructive behaviors like scratching or licking themselves excessively or chewing on their toes. Such behaviors are also common with dogs that have obsessive-compulsive disorders.

A medication like Prozac could be helpful in these instances. However, it should be noted that Prozac is just one aspect of treatment. “It absolutely has to be coupled with behavior modification to train these dogs not to do the behavior that we want to stop,” Dr. Attas emphasizes. “Oftentimes people will come to us because their dog has an issue and say, ‘Can’t you just give my dog Prozac?'” Because of the way Prozac acts in the brain, it may help to diminish a dog’s emotions, but it’s not going to solve the problem entirely.

Aggressive Behavior

In addition to treating fear and anxiety, fluoxetine can help with aggressive behavior in dogs. If you’re using this drug as part of therapy for aggression, you need to be very cautious. “Sometimes the signs that a dog is feeling nervous (e.g., dilated pupils) or might act aggressively (e.g., pricked ears) are dampened when they’re on Prozac,” Dr. Attas explains. “So, they might not give you that growl before they bite, or they might not raise their fur if they get really nervous.” The risk of them biting without giving any advanced warning can lead to injury to yourself or other people and animals.

Depressed Mood or Behavior

Sometimes people use the terms “depressed” and “depression” interchangeably, but they’re not the same. “Depression is a clinical disease for which medication is needed,” Dr. Attas says. “Being depressed is an exaggerated emotional response, usually to something that’s happened in your life.” For example, if you lost your job or broke up with your partner, you wouldn’t take Prozac. Instead, you would do something to change your mood like spending time with friends or listening to soothing music.

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It’s the same for dogs except, in veterinary medicine, they don’t recognize a clinical diagnosis of depression. So, if you come to the vet clinic saying your dog is depressed, your veterinarian will want to know more about the symptoms you’re noticing, and they will make the diagnosis. They’ll likely want to rule out any possible underlying medical causes that could lead to a change in your dog’s behavior. Typically, what people are calling depression is a lack of enrichment.

Dogs like to be with people and other dogs. “If we don’t give them enough enrichment in their lives, they’re going to act like they’re depressed,” she says. “But that’s not clinical depression because we can fix that purely with behavior modification.” Prozac can help with anxiety, but it won’t make your dog happier if they’re bored or grieving the loss of another pet in the home.

What Are the Side Effects of Fluoxetine?

Fluoxetine belongs to a class of medications called selective serotonin reuptake inhibitors (SSRIs). Serotonin is a chemical messenger in the brain that plays a role in regulating different functions including sleep, mood, and digestion. As an SSRI, Prozac works by preventing the reuptake of serotonin, so there’s a higher level of this chemical in the brain which helps improve communication between brain cells.

Since fluoxetine influences chemicals in the brain, it’s not considered a benign drug. In fact, the most common side effects are loss of appetite, drowsiness. Other side effects include vomiting, diarrhea, shaking, restlessness, panting, whining/vocalization, loss of affect, incoordination, excessive saliva, and weight loss. Serious/severe side effects include seizures, aggression, and excessive/persistent vomiting.

Symptoms like loss of affect tend to diminish the longer the patient is on the drug. It can take at least a month for the drug to reach an effective level to prompt behavioral changes. In general, Prozac is a “really safe drug,” Dr. Attas says. “Not that I recommend anybody overuse it, but even taking more than the prescribed amount doesn’t really present immediate medical concerns.”

Be sure to tell your veterinarian if your dog is currently taking any medications, including vitamins or supplements. This moderate-acting medication’s effects can be longer in pets with liver or kidney disease. Dr. Klein, AKC’s Chief Veterinarian, notes that Fluoxetine shouldn’t be used in pets with a history of seizures or in pets that are on medications that lower the seizure threshold. It should not be used in pets that are allergic to it, pets taking monoamine oxidase inhibitors (MAOIs), pets younger than 6 months of age, or aggressive pets. Use cautiously in pets with diabetes mellitus, severe liver disease, or in pregnant or lactating pets.

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Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking. The following medications should be used with caution when given with fluoxetine: anticoagulants, aspirin, buspirone, cyproheptadine, diazepam, alprazolam, diuretics, flea/tick collars, insulin, isoniazid, MAOIs, methadone, NSAIDs, pentazocine, phenytoin, propranolol, metoprolol, St. John’s wort, tramadol, tricyclic antidepressants (TCAs), or trazodone.

How Do Vets Decide on Dosage?

Prozac can be obtained from a human or veterinary pharmacy. The concentrations start at 10 milligrams for humans and can be prepared in smaller dosages for dogs and other small animals. If your dog isn’t a fan of taking pills, you can hide it in a treat like peanut butter. Also, there are compounding pharmacies that can flavor a medication with beef, liver, or bubble gum to make it more palatable for dogs.

Typically, the vet will start your dog on a very low dose of the medication. They’ll slowly increase the dose as your dog gets used to it. Keep in mind that “a drug like Prozac does need some time to raise an effective blood level where we’re going to see some effects,” Dr. Attas says. For instance, if your dog started taking Prozac today, you could see some side effects the following day. They might be a bit drowsy or have a decreased appetite.

“But it’s not going to affect how they’re behaving until we have an effective blood level which could take two to four weeks,” she says. Her recommendation is to start low, get them through the period where they’re having side effects, and then gradually increase the dose. While your dog is adjusting to the medication, they’ll need to meet with the vet periodically who will perform a physical examination and monitor their blood work.

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What Are Some Risks of Taking Fluoxetine?

Before embarking on this treatment plan, it’s important to consider whether this drug will make a significant difference in your dog’s behavior. “If it’s not going to do that, you shouldn’t use this drug,” Dr. Attas says. “And the only way it’s going to make a significant difference is if the family members are willing to commit the time to do behavioral training.”

Prozac is given orally and cannot be used in pregnant dogs or people. As with any prescription or over-the-counter medication, make sure to store fluoxetine far from the reach of pets and children. When you and the vet have decided that it’s time to take your dog off fluoxetine, it’s important to wean them off rather than stopping the medication abruptly.

Another caution has to do with administering more than one drug at the same time. When used together, these drugs can interact and make your dog sick. For example, using Trazodone or clomipramine in combination with Prozac can lead to something called serotonin syndrome, she explains. Like Prozac, these drugs tend to increase the level of serotonin in the brain, causing mild to severe and potentially fatal symptoms. These include fast heart rate, high blood pressure, tremors, and in more serious cases, high body temperatures, seizures, and muscle breakdown.

Other drugs to avoid combining with Prozac are Monoamine oxidase inhibitors (antidepressants), opioids, and some herbal drugs like St. John’s Wort, Panax ginseng, nutmeg, and yohimbe. That’s why it’s so important to speak with your vet about all the medications your dog is taking including natural products and herbs. “Supplements are still chemicals whether you find them in nature or make them in a laboratory, and they can interact with other medications,” she adds.
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