Fluoxetine for Dogs: Uses, Side Effects, and Precautions

Fluoxetine for dogs (Reconcile®) is a great option for managing separation anxiety, social anxiety, noise phobias, and other types of behavioral problems in many dogs. Integrative veterinarian Dr. Julie Buzby explains the uses, side effects, drug interactions, and precautions for fluoxetine so you can more confidently give it to your dear dog.

Anxiety in dogs is much more common than many people realize. In fact, researchers (and veterinarians) are finding that since the COVID-19 pandemic, anxiety diagnoses in dogs have skyrocketed.

Different dogs may have different triggers, but one of the most significant changes is in the number of dogs with separation anxiety. One study estimated as much as a 700% increase in separation anxiety in dogs between 2020 to 2022!

Plus, studies showed an increased number of dogs with a fear of strangers, other animals, loud noises, or new places. These changes may also be rooted in the life transitions that occurred during and after the pandemic.

The good news? Just like people, dogs can benefit from certain medications to help calm their minds and ease their fears. One option your veterinarian might suggest is fluoxetine for dogs.

What is fluoxetine for dogs?

Fluoxetine is an antidepressant that may help alleviate anxiety and other behavioral problems in dogs. It is sold under two main trade names—Prozac® (human version) or Reconcile® (dog version). Prozac, Reconcile, and generic fluoxetine are only available by prescription.

Prozac® is FDA-approved for use in humans. However, veterinarians have commonly prescribed fluoxetine for dogs and other small animals off-label to manage anxiety-related behavior for many years, especially before Reconcile was available.

In 2007, the FDA approved a dog-specific version of fluoxetine called Reconcile®. It is labeled specifically for managing separation anxiety in dogs in conjunction with behavior modification training. Reconcile is a flavored chewable tablet. This makes it much more appealing for dogs to take as a treat or mix in with a meal.

Note: If you are taking fluoxetine and feel your dog could benefit from it too, it is very important to make an appointment with your vet. DO NOT try sharing some of your own fluoxetine (or any other antidepressant) with your dog.

What does fluoxetine do for dogs?

Fluoxetine belongs to a group of medications called SSRIs, or selective serotonin reuptake inhibitors. In simple terms, these medicines help boost the amount of serotonin in the brain. Serotonin, often nicknamed the “feel-good” chemical, helps regulate mood, ease anxiety, support healthy sleep, and even aid digestion.

When serotonin levels are too low, dogs (and people) can experience increased stress or anxiety. However, since fluoxetine works by maintaining higher serotonin levels in the brain, it can help dogs feel calmer, more balanced, and less anxious.

What is fluoxetine used for in dogs?

Fluoxetine has several valuable uses in veterinary medicine, including managing:

Separation anxiety

Separation anxiety often starts when your dog notices signs that you’re about to leave. Simple parts of your routine, such as putting on shoes, grabbing your keys, or turning off the TV, can tip him or her off. Once your dog realizes you’re heading out, he or she may become extra clingy, bark or whine, or even act out destructively.

Social anxiety

Some dogs may become anxious when exposed to unfamiliar animals and/or people at the vet’s office, pet supply store, dog park, etc. They may cower and shake in terror, or bark and become aggressive.

Spatial or locational anxiety

Dogs with locational anxiety may become fearful or nervous when they visit certain places such as the vet hospital or grooming salon. For some dogs, going anywhere outside their safe space at home can be enough to cause anxiety.

Aggression

Fearful or anxious dogs can sometimes be aggressive as a defense mechanism (the “fight” aspect of the fight or flight response). If your dog falls into this category, it’s essential to approach managing his or her anxiety carefully. The best plan seems to be a combination of medication such as fluoxetine and training or behavior work. Ideally, you would work closely with a board-certified veterinary behaviorist or a general practice veterinarian with a special interest in behavior.

One thing to keep in mind with fluoxetine is that it can sometimes “mask” a dog’s usual warning signs. For example, dogs may not growl, raise their hackles, or show those big, wide eyes the way they usually would before snapping. That means you need to be extra cautious in situations that make your dog feel anxious. He or she may still be scared and defensive, and bite without giving you the usual cues beforehand.

Obsessive-compulsive behaviors (OCD)

Dogs with obsessive-compulsive disorder (OCD) may repetitively exhibit unpleasant or undesirable habits such as:

• Tail-chasing
• Flank (or blanket) sucking
• Licking their paws until sores develop (lick granulomas in dogs)
• Pacing and/or spinning
• Chasing lights or shadows

Fluoxetine may provide relief from these urges.

Noise phobias

Dogs who suffer from thunderstorm or fireworks phobias can be absolutely miserable at certain times of the year. Many fast-acting, situational calming medications either don’t take effect in time or cause too much sedation and have more extended recovery periods than necessary.

Thus, fluoxetine can be a good solution during thunderstorm season or other times when dogs may need sustained coverage for anxiety-inducing noises. (However, as discussed in a bit, your dog needs to start taking the fluoxetine 4-8 weeks before the time you anticipate needing it.)

Inappropriate urine marking

While this is more commonly a bad habit in cats, dogs also engage in behaviorally driven inappropriate urination. If your vet has ruled out medical conditions like a urinary tract infection (UTI in dogs) or incontinence in dogs, he or she may recommend trying fluoxetine.

Does fluoxetine work for dogs?

Different dogs might need slightly different medications or behavioral modification plans to manage their anxiety, but overall fluoxetine does seem to work well for many dogs. In a study looking at 88 dogs taking fluoxetine for behavioral disorders, 59% of owners reported improvement, 32% saw no change, and 9% thought their dog’s behavior worsened. (Note: The dogs in the study were also working through a behavior modification plan, and some of them were taking another anti-anxiety medication concurrently.)

When looking at the different types of behavioral issues in the study more closely, 69% of owners of dogs with anxiety, 55% of owners of dogs with aggression, and 50% of owners of dogs with other problems (OCD, self-mutilation) felt their dog improved on fluoxetine plus a behavior modification plan.

In a different study, 72% of dogs taking Reconcile and participating in a behavior modification plan showed an improvement in their separation anxiety. This number was only 50% in the placebo group (placebo medication plus behavioral modification plan).

What is the fluoxetine dose in dogs?

Your veterinarian will calculate your dog’s fluoxetine dose based on his or her bodyweight and then select the appropriately-sized pill or liquid. Generic fluoxetine and Prozac come in tablets (10 mg, 15 mg, and 20 mg) and capsules (10 mg, 20 mg, and 40 mg). Reconcile is available as a chewable tablet in 8 mg, 16 mg, 32 mg, and 64 mg strengths. It is also possible to get it compounded into a flavored liquid. (There is liquid fluoxetine for humans but it may not be safe for dogs.)

Note: Some veterinarians and veterinary behaviorists feel that the dog-specific product Reconcile works better for their patients than generic fluoxetine or Prozac. However, there is not a consensus on this, so your veterinarian will do what he or she feels is right for your dog.

How do you give your dog fluoxetine?

Dosing frequency for fluoxetine is once daily (every 24 hours) by mouth. Since it could interefere with sleep, giving fluoxetine in the morning is best unless your vet says otherwise.

Your vet may recommend starting with a lower dose for the first few days. This helps ensure your dog can tolerate the medication before you increase the dose to the full prescribed amount. It also gives you time to watch for any side effects and let your vet know if something doesn’t seem right.

You can give fluoxetine on an empty stomach. But if your dog develops digestive upset, try giving the next dose with a meal or a small treat. 

If your dog enjoys getting a tasty snack with his or her medication, steer clear of aged cheeses. It might sound like an odd warning, but many aged cheeses contain a compound called tyramine. This compound can raise your dog’s heart rate, increase his or her blood pressure, and even make him or her feel jittery. So, if your pup happens to be a true cheese lover, skip the Parmesan, Cheddar, Gouda, or Swiss.

What if your dog misses a dose of fluoxetine?

While stopping fluoxetine cold turkey can cause unpleasant side effects, generally missing one dose isn’t going to cause issues for most dogs. If you do miss a dose of fluoxetine, do not give your dog a double dose to make up for the missed dose. Instead, just monitor your dog at home and restart dosing according to the usual dosing schedule.

That being said, if you have questions about your dog’s dosing schedule or have missed multiple doses, don’t hesitate to contact your vet. There are some situations where the vet may have you give the fluoxetine when you remember rather than waiting for the next regularly scheduled dose.

Warning: Don’t stop giving your dog fluoxetine abruptly

If it seems like fluoxetine isn’t helping your dog’s behavior, do not stop the medication abruptly. Just like people, dogs go through withdrawal if you stop antidepressants too quickly. The side effects of stopping fluoxetine in dogs rapidly can include nausea, shaking, or worsening anxiety—the very thing you were trying to decrease in the first place. Always talk with your vet before making any changes to your dog’s medication regimen.

How long does it take for fluoxetine to start working?

It can take 4-8 weeks to see the full effects of fluoxetine, so don’t be surprised if it doesn’t seem to be working at first. Your veterinarian will likely advise you wait to assess the effectiveness of fluoxetine until you have been administering it consistently for a month or two. After that point, the vet may consider a dose adjustment. Or he or she might recommend transitioning to a different medication if fluoxetine still doesn’t seem to be working well.

Should your vet recommend stopping the fluoxetine, he or she will probably have you taper it down over 3-5 weeks if your dog has been on the fluoxetine for at least 8 weeks. If your dog has only been on fluoxetine for a short time, a more rapid taper or no taper at all may be fine. Your vet will instruct you on what is safest for your dog.

Do dogs on fluoxetine need special monitoring?

Before starting fluoxetine, your veterinarian will likely recommend blood tests for dogs to evaluate your dog’s liver and kidney function. SSRIs like fluoxetine are metabolized in the liver and excreted by the kidneys, so it’s essential to be sure that your dog’s liver and kidney function is normal.

Monitoring blood levels of fluoxetine is not necessary since plasma levels of SSRIs don’t reflect a clinical response to treatment. Instead, your veterinarian will talk with you about how your dog is doing in terms of anxiety levels and side effects. Then he or she will make recommendations from there.

What are the fluoxetine side effects in dogs?

Fluoxetine does have the potential to cause side effects, which can be mild or severe depending on your dog’s individual tolerance. Side effects of fluoxetine may be physical, behavioral, or both.

Physical side effects of fluoxetine

 When starting fluoxetine, it’s not uncommon for dogs to experience:

• Drooling (hypersalivation)—You might notice your dog keeps licking his or her lips or has drool hanging from the mouth.
• Vomiting—GI upset such as vomiting is common when starting fluoxetine. Giving it with food can help.
• Diarrhea– Your might notice your dog is having diarrhea but acting fine.
• Loss of appetite— Due to stomach upset, your dog may not want to eat as much as usual.
• Unsteady gait (ataxia)— You might notice your dog is wobbly and off balance. This can be a more serious side effect so contact your vet promptly if you see it.
• Weight loss—Around one-third of dogs on fluoxetine will lose weight.

It’s essential to monitor your dog closely and report any new or unusual symptoms to your vet as soon as possible. These side effects may be short lived in some dogs. But if your dog experiences more severe side effects, your veterinarian may advise weaning your dog off fluoxetine.

Behavioral side effects of fluoxetine

Dogs on fluoxetine may experience behavioral changes such as:

• Lethargy or increased drowsiness—A lethargic dog may seem tired or sedate, or want to lay around and sleep more than usual.
• Shaking—Your dog may appear to have mild tremors or be shaking.
• Restlessness—Sometimes dogs will pace or act like they can’t settle down.
• Panting—Increased panting may go along with the restlessness.
• Whining—Dogs on fluoxetine may whine or vocalize more.

As with the physical side effects, these symptoms may be transient during the initial dosing period. But if you observe a worsening of any signs, contact your veterinarian immediately.

What are the signs of a fluoxetine overdose in dogs?

If a dog accidentally gets too much fluoxetine, the side effects can be much more serious. This may occur when a dog inadvertently receives a double dose, or in situations where the dog receives a human dose of fluoxetine. Signs of overdose may include:

• Seizures –—Dogs who have had seizures before may be more likely to have them again.
• Serotonin syndrome –—This is a dangerous reaction that can happen if there’s too much fluoxetine in your dog’s system, or when you combine fluoxetine with certain other medications (more on this in a bit). Serotonin syndrome can cause seizures and other severe reactions, including death.
• Cardiovascular changes—Dogs who get an overdose of fluoxetine may have an elevated heartrate or high blood pressure (hypertension in dogs).
• Gastrointestinal issues – Worsening vomiting or diarrhea is possible.
• High body temperature—Due to the severe tremors or muscle spasms, the dog might experience hyperthermia (elevated temperature).
• Behavioral changes—Dogs may exhibit extreme anxiety, hyperexcitability, aggression (even in dogs who had not previously shown aggressive behaviors), or tremors.
• Stiff or rigid muscles—Your dog may seem tense and unable to relax.

Are there dogs who should not take fluoxetine?

Fluoxetine may not be suitable as a therapeutic option for all dogs with anxiety or behavioral issues. In fact, there are several situations in which fluoxetine is explicitly not recommended for use in dogs.

Dogs who have seizures

Fluoxetine should not be used if there is a history of seizures in dogs or the dog is on other medications that lower the seizure threshold. Examples include phenothiazine drugs like acepromazine or anesthetic drugs like ketamine.

Dogs with a fluoxetine allergy

Dogs with a known allergy to fluoxetine or other SSRIs (like Zoloft®/sertraline or Paxil®/paroxetine) should avoid taking it.

Diabetic dogs

Fluoxetine can alter blood glucose levels, disrupting insulin regulation in cases of diabetes in dogs. Thus, diabetic dogs should not take it or should take it with care.

Dogs with liver disease

The liver metabolizes fluoxetine, so sometimes being on it can cause high liver enzymes in dogs or even lead to liver problems if used long-term. In situations where liver disease in dogs is already present, the body may not be able to clear the drug as quickly. This means fluoxetine can build up to unsafe levels in the brain, increasing the risk of side effects.

Fluoxetine can also interfere with how the liver breaks down other medications. This may make those drugs stay in the body longer and potentially reach harmful levels.

Young, pregnant, or nursing dogs

Fluoxetine is contraindicated in puppies under 6 months of age. Plus, since fluoxetine is detectable in the milk, it poses a risk of toxicity to nursing puppies if given to a pregnant or lactating dog.

Aggressive dogs

As mentioned earlier, dogs with known aggression issues may experience a paradoxical worsening of their aggression. They may not show the normal warning signs before they become aggressive, which increases the risk of them hurting another animal or person.

Dogs with kidney problems

Since the kidneys remove fluoxetine from the body, the vet may recommend using a lower dose of fluoxetine or not using it at all in the face of moderate to severe kidney disease in dogs.

Which drugs should not be given with fluoxetine?

Fluoxetine may interact negatively with certain medications, foods, and even natural supplements. For this reason, it’s essential to inform your veterinary team of everything your dog is currently taking. This doesn’t just mean prescription drugs. It also includes supplements and topical products like flea and tick collars.

Below are some of the most common interactions to be aware of:

Monoamine oxidase inhibitors (MAOIs)

Giving fluoxetine along with an MAOI can be very risky and may cause a serious condition called serotonin syndrome. This is the case because MAOIs increase the levels of neurotransmitters (signaling chemicals) in the brain, including serotonin. Two common MAOIs used in veterinary medicine are:

• Selegiline for dogs (Anipryl®)—Veterinarians may prescribe selegiline for dogs with doggy dementia (canine cognitive dysfunction) or Cushing’s disease in dogs.
• Amitraz (Mitaban® dip or Preventic® collars)—These are anti-parasitic medications that work against fleas, ticks, and mites. While Amitraz targets an insect’s nervous system, dogs that accidentally absorb or ingest it can also experience severe side effects.

It’s essential to remember that MAOIs and SSRIs like fluoxetine should not be used simultaneously to treat your dog for any condition. If your dog is on an SSRI and a MAOI is recommended, there should be at least a 6-week washout period between ending the SSRI and starting the MAOI. Conversely, if your dog is on an MAOI and your vet recommends an SSRI, the washout period should be at least 2 weeks. The difference in washout times is due to the fact that SSRIs stay in the body longer than MAOIs.

Serotonin receptor antagonists and reuptake inhibitors (SARIs)

SARIs work similarly to SSRIs by regulating serotonin levels in the brain. Drugs in this class, like trazodone for dogs, are more commonly used for short-term, situational anxiety like thunderstorm phobias or vet visits.

You can give fluoxetine and trazodone together, but doing so raises the risk of side effects, including serotonin syndrome. Monitor your dog closely if he or she is on both medications. 

Drugs that lower the seizure threshold

Some medications make dogs more likely to have a seizure than they normally would. In other words, they can “lower the seizure threshold.” Common medications in this category include:

• Acepromazine and chlorpromazine (phenothiazines)
• Clomipramine and amitriptyline (tricyclic antidepressants)
• Ketamine (dissociative anesthetic) 
• Tramadol for dogs (opioid)

Since fluoxetine can also lower the seizure threshold, combining it with other drugs with the same effect may make a dog more likely to have a seizure.

Drugs that are metabolized via the cytochrome P-450 enzyme system

Some medications are broken down in the liver by an enzyme system called cytochrome P-450. Fluoxetine can interfere with this process, slowing down how the liver clears those drugs. That means the other medication can build up to higher levels in the body, which raises the risk of side effects or even toxicity. A few common examples of drugs that use the P-450 system include:

• Buspirone (anti-anxiety) 
• Cimetidine (acid blocker)
• Diazepam, Alprazolam (benzodiazepines)
• Phenobarbital, Phenytoin (antiepileptics)

Other medications that may interact poorly with fluoxetine

Additionally, there are a few other medications that should not be combined with fluoxetine.

• Isoniazid (antibiotic)
• Warfarin (anticoagulant)
• Cyproheptadine (antihistamine, appetite stimulant)
• Propanolol, metoprolol (beta blockers)
• Diuretics (furosemide, spironolactone)
• Aspirin (NSAIDs)
• Pentazocine (opioid analgesic)

Beware of combining natural supplements with fluoxetine

If you’ve been looking into natural supplements for your dog, it’s important to remember that “natural” doesn’t always mean “safe.” Some popular supplements can be dangerous for dogs taking fluoxetine. They include:

• St. John’s Wort
• THC (cannabis) products
• Ginseng
• Nutmeg
• L-tryptophan (found in some calming supplements)
• 5-HTP
• Melatonin for dogs

The reason for this is that the body converts supplements like tryptophan and 5-HTP into serotonin. As was the case with the MAOIs and SARIs, excessive serotonin can lead to serotonin syndrome.

What medications can you combine with fluoxetine?

There is certainly a long list of medications that don’t play well with fluoxetine. However, the good news is there are still plenty of common pain medications, antibotics, and other drugs that don’t interact poorly with it.

Additionally, sometimes your vet can safely combine other behavior-modifying medications with fluoxetine. For example, gabapentin for dogs can give your dog extra support for managing anxiety when used with fluoxetine. If you feel that fluoxetine isn’t helping your dog enough or consistently, talk to your veterinarian about your options.

Work with your vet to manage your dog’s anxiety

Every dog’s anxiety is unique, and finding the best way to manage your dog’s symptoms can sometimes feel like a daunting task. That said, fluoxetine can be a valuable tool to help your beloved dog feel calmer and more confident in his or her daily routine.

Working closely with your veterinarian is the best way to ensure that your dog’s symptoms are properly managed. With consistency and patience, you can give your dog the support and confidence he or she needs to handle the “big scaries” in life.

How has fluoxetine helped your dog?

Please comment below.