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What is serotonin syndrome in dogs?

What to Expect if Your Dog is On Trazodone

This medication can be a useful tool for dogs who struggle with anxiety, fear, or other behavioral disorders.

jenna stregowski
By Jenna Stregowski, RVT March 22, 2022
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woman cuddling a black french bulldog
Credit: Tempura / Getty

On This Page

  • What is Trazodone Used For?
  • Potential Side Effects
  • Dosage for Dogs
  • Can Dogs Overdose on Trazodone?
  • Interactions and Warnings

Just like people, many dogs experience fear or anxiety from time to time. Unfortunately, also like people, some struggle with severe anxiety that affects their quality of life. The good news is that modern medicine can help. Trazodone is one of several anti-depressant drugs used for dogs diagnosed with anxiety and other behavioral disorders.

Some pet parents hesitate to use medication to address behavior concerns because they worry about «drugging» their dogs. Many would rather focus on methods like training and socialization to reduce fear and anxiety. While these techniques can help some dogs overcome their undesirable feelings and behaviors, others need a little extra help. Drugs like trazodone are not intended to completely resolve behavioral disorders; they are tools to be used along with gentle behavior modification techniques that include positive reinforcement training and socialization.

It’s hard to watch your precious pooch suffer through unwanted feelings and urges, but you’re not in this alone! Work closely with your veterinarian to develop the right treatment plan for your dog. Your vet may refer you to a veterinary behaviorist or certified animal behavior consultant for additional support.

What Is Trazodone Used for in Dogs?

Trazodone is an antidepressant drug—specifically a selective serotonin reuptake inhibitor and serotonin type 2 receptor antagonist. Serotonin is a neurotransmitter, a type of chemical messenger in the brain that relays signals to the neurons (brain cells). Serotonin plays an important role in several bodily functions, including psychological aspects such as mood. Drugs like trazodone work by inhibiting serotonin resorption, thus increasing the level of serotonin in the brain.

Trazodone is often used in humans to treat depression and insomnia. In veterinary medicine, it’s sometimes prescribed to treat behavioral disorders in dogs and cats. Dogs with fear and anxiety may benefit from trazodone therapy. Veterinarians may prescribe it to reduce fear and anxiety in stressful situations, like thunderstorms, fireworks, vet visits, and boarding. Because it also has sedative effects, it’s sometimes used in conjunction with anesthesia drugs for surgery and other medical procedures. In addition, trazodone has been used to help calm dogs who need to be confined and to have their exercise restricted while they recover from surgery or injury.

Anxiety makes it difficult for dogs to learn, so training and socialization can be less effective for a nervous dog. Trazodone can help reduce anxiety enough so that dogs can actually learn from techniques like desensitization and counterconditioning exercises, training sessions, and socialization events. It’s important to work closely with your dog while using trazodone—the medication alone will not address the root of the behavior. For help with training and socialization techniques, seek assistance from a certified animal behaviorist or trainer.

Trazodone is available in generic forms as well as the brand names Oleptro and Desyrel. There is no veterinary-labeled form of trazodone, but some vets keep it in stock. It can also be purchased from a human pharmacy with a prescription from your veterinarian.

What Are Potential Trazodone Side Effects in Dogs?

Dogs generally tolerate trazodone well, but the following side effects may occur:

  • Sedation/drowsiness
  • Lethargy
  • Vomiting
  • Colitis (inflammation of the colon)
  • Ataxia (drunken gait)
  • Heart arrhythmia
  • Increased appetite

Some dogs will respond poorly to trazodone and experience increased anxiety or agitation. Stop this medication and contact your vet if trazodone is making your dog’s fear or anxiety worse.

Trazodone Dosage for Dogs

Trazodone is given to dogs orally as a pill. The recommended dosage of trazodone for dogs generally ranges from 1 to 19 milligrams per kilogram of the dog’s mass, per day. Dogs with chronic behavioral disorders may be prescribed the extended-release tablets to be taken daily. However, trazodone can be used on an as-needed basis with a fast onset as long as you are not using extended-release tablets. This can be very helpful for sudden scary events, like thunderstorms.

Can Dogs Overdose on Trazodone?

It’s possible for dogs to overdose on trazodone if they are accidentally given too much or they get into the bottle of pills. Be sure to keep this and other medications out of your dog’s reach. Trazodone overdose can cause serotonin syndrome, a dangerous condition that may cause the following:

  • Vomiting
  • Diarrhea
  • Depression
  • Drooling
  • Hyperthermia (high body temperature)
  • Seizures
  • Blindness
  • Trouble breathing
  • Paralysis
  • Coma
  • Death

Seek professional help if your dog gets an overdose of trazodone. Call your local veterinarian, a nearby animal emergency center, or a pet poison control service like ASPCA Animal Poison Control at (888) 426-4435 or Pet Poison Helpline at (855) 764-7661. You may be advised to induce vomiting if the overdose occurred within the last hour. Your dog may also need veterinary supportive care to manage symptoms and provide comfort.

Trazodone Drug Interactions and Warnings

Several drugs can interact with trazodone, so be sure to tell your vet about all of your dog’s medications and supplements. If trazodone is used with other drugs that affect serotonin, it increases the risk of serotonin syndrome and other complications. This includes other SSRIs, monoamine oxidase inhibitors (MAOIs), certain antifungal drugs (like ketoconazole and fluconazole), and certain antibiotics (like erythromycin).

Selegiline for Dogs: A Helpful Medication for Canine Cognitive Dysfunction

Selegiline for dogs can be a great option for some pups (and their parents) who are struggling with the effects of canine cognitive dysfunction, commonly known as doggy dementia. Integrative veterinarian Dr. Julie Buzby explains how selegiline works and when to expect to see improvement. She also goes over the side effects and precautions so you can have all the facts you need to make informed choices for your dog.

Senior Terrier mix lying in a field of purple and yellow flowers, photo

A while back, a veterinary client brought Yoshi, an 11-year-old, Labrador-Hound mix, to see me. Yoshi and I met previously when his owner noticed signs of dementia in dogs. This condition, which is also known as canine cognitive dysfunction syndrome or canine cognitive dysfunction (CCD), involves a decline in cognitive function and is fairly common in older dogs. Affected dogs may be less engaged with their families, show increased anxiety, become disoriented, forget things or people they once knew, or have trouble settling down and sleeping at night.

I used a canine cognitive dysfunction checklist to help reach a diagnosis for Yoshi at that earlier visit. His mom and I discussed some brain games and other ways to help keep his mind as sharp as possible. I also advised her to closely monitor Yoshi for signs that his CCD was getting worse.

Things were going well at first, but recently she noticed he wasn’t sleeping through the night. It also seemed like he was pacing more than he was previously. My veterinary client wanted to pursue additional treatment options for Yoshi to help keep him comfortable during his senior years.

I told her there is a medication called selegiline for dogs that could be a great option. She was excited to know there was a treatment available for Yoshi, but understandably wanted to know a bit more about it before deciding to try it.

What is selegiline for dogs?

Currently, selegiline is the only FDA-approved drug for treating canine cognitive dysfunction in veterinary medicine, which will be the focus of this article. Additionally, it is approved by the FDA for the treatment of pituitary-dependent Cushing’s disease in dogs. However, selegiline typically isn’t as effective at managing Cushing’s disease as other medications like trilostane for dogs or mitotane.

Selegiline is available under multiple different brand names including: Anipryl®, Eldepryl®, l-deprenyl, Selgian®, Carbex®, and Zelapar®. It also is available in a generic form.

Senior Terrier mix lying in the sheets on a bed, photo

How does selegiline help dogs with canine cognitive dysfunction?

Selegiline is a monoamine oxidase inhibitor (MAOI). This means that it blocks an enzyme known as monoamine oxidase (MAO) and prevents the enzyme from functioning. Dogs have these enzymes in their brain, liver, and GI tract. Selegiline specifically targets the enzymes in the brain.

These MAO enzymes remove extra amounts of dopamine in the brain. Dopamine is a chemical that aids in communication throughout the brain. It is also known as a “feel good” chemical. This means that dopamine helps people and dogs recognize things that are pleasurable, such as eating.

In dogs with CCD, the MAO enzymes work too hard and get rid of too much dopamine in the brain. The excess removal of dopamine causes the clinical signs we see in our senior dogs with CCD.

Since selegiline is an MAOI, it inhibits the MAO enzymes and prevents them from removing excess dopamine. Therefore, more dopamine stays in the brain, and your dog’s CCD symptoms should hopefully improve.

Does selegiline work for dogs?

A study in Veterinary therapeutics: research in applied veterinary medicine indicated that approximately 77% of dogs with CCD showed improvement on selegiline. This means that while it isn’t going to be the solution for every dog, it does have a pretty decent chance of being effective for many dogs.

In most cases, pet owners begin to notice an improvement in their dog’s cognitive dysfunction after approximately one month of treatment. However, it may take up to 12 weeks to see the full effects. As with any medication, it can require some trial and error to find the perfect dose for your dog. And some dogs may respond faster than others.

Any time you start giving a new medication to your dog, it is very important to watch him or her for changes in behavior or possible side effects. Noticing early on how your dog is responding to selegiline will be important to help your veterinarian determine the next steps.

Senior yellow lab lying down on the floor in the living room, photo

What is the dosage for selegiline?

Generally, dogs will start out taking selegiline once a day (i.e. every 24 hours). It is commonly available as tablets that you can give your dog by mouth. If your dog won’t take pills, your veterinarian can also order a flavored selegiline liquid from a veterinary compounding pharmacy. You still need to give the liquid by mouth, but this is sometimes easier to administer than a pill. Additionally, selegiline comes in a transdermal patch that your vet can apply to your dog’s skin.

Selegiline is available as 1.25 mg, 2 mg, 4 mg, 5 mg, 10 mg, 15 mg, 20 mg, 30 mg, 40 mg, and 80 mg tablets as well as 6 mg/24 hours, 9 mg/24 hours, and 12 mg/24 hours transdermal patches.

Your veterinarian will determine what form and dose of selegiline is best for your dog. The decision depends on your dog’s clinical signs, weight, and other medications your dog is taking. It is very important that you follow your veterinarian’s instructions and do not make changes to the selegiline dose without consulting your veterinarian first.

What if I miss a dose?

If you realize you forgot to give your dog a dose of selegiline, there is usually no need to panic. You can give the missed dose when you remember. However, it is best not to give doses too close together in order to avoid over-dosing your dog. If it is close to time for the next dose. skip the missed dose and give your dog the next dose at the usual time.

What are the possible side effects of selegiline?

When dosed and used appropriately, selegiline is usually a safe medication. On average, only 5% of dogs have side effects to selegiline. Common side effects include:

  • Vomiting
  • Diarrhea
  • Decreased appetite
  • Excessive drooling
  • A lethargic dog/ decreased energy
  • Tremors
  • Itchiness
  • Disorientation
  • Impaired hearing

Terrier mix lying down and sleeping as an example of lethargy—one possible side effect of selegiline for dogs, photo

Side effects are most likely to occur in dogs who are sensitive to selegiline or when used at higher doses. If you see any of these signs or have other concerns about your dog’s health or behavior while taking selegiline, please contact your veterinarian promptly.

The most common side effects in dogs who receive an overdose of selegiline include the ones listed above plus weight loss, abnormal pupil responses, and pacing. If you think you accidentally over-dosed your dog, contact your veterinarian immediately. Monitor your dog closely for the side effects described above and follow your veterinarian’s advice.

Are there situations where selegiline isn’t a good idea?

When talking with your dog’s veterinarian about the possibility of starting selegiline, be sure to mention any clinical signs you have seen at home. For example, selegiline should be used with caution in dogs who are aggressive. While it is rare, selegiline can increase aggression.

Your veterinarian also needs to know if your dog is pregnant, lactating, or a potential breeder. As of now, researchers have not conducted enough studies to determine whether selegiline is safe in pregnant or nursing dogs.

Additionally, it is very important to mention any medications your dog is taking. This includes prescriptions, over the counter drugs, supplements, and natural remedies. Medications, including natural ones, can interact with selegiline and cause undesired side effects.

Why does it matter what other medications my dog is on?

Combining selegiline with certain other medications can be risky. The most concerning consequence would be the development of serotonin syndrome.

Serotonin syndrome occurs when the levels of serotonin in the brain are too high. While serotonin does act in the brain to create feelings of happiness and well-being, too much of it is a bad thing. Clinical signs of serotonin syndrome include:

  • Increased heart rate
  • Tremors
  • Enlarged pupils
  • Fever
  • Difficulty breathing
  • Hyperactivity
  • High blood pressure (i.e. hypertension in dogs)
  • Old dog seizures

Senior Golden Retriever at a camp site, photo

If you suspect that your dog is developing serotonin syndrome, please call your veterinarian immediately. If it is ignored, serotonin syndrome can be deadly for your dog due to a rapid elevation in blood pressure.

Drug combinations that increase the risk of serotonin syndrome

Serotonin syndrome is most likely to occur if selegiline is used in combination with other MAO inhibitors. These include amitraz (used for killing fleas and ticks), and many other medications.

Taking selegiline at the same time as selective serotonin reuptake inhibitor (SSRI) drugs (i.e. trazodone or fluoxetine) or tricyclic and tetracyclic antidepressants (i.e. clomipramine) can also lead to serotonin syndrome. Vets most commonly prescribe these medications as a treatment for anxiety. Fluoxetine can stay in a dog’s body for a long time, so typically you need to wait several weeks after stopping it before starting selegiline.

This is far from an exhaustive list of things that could increase the chances of serotonin syndrome, which is why it is so important to keep your vet informed of anything your dog might be taking—medication or otherwise.

Other drug interactions

Additionally, selegiline should not be used at the same time as phenylpropanolamine. Vets often use this medication to help with urinary incontinence in older dogs. Generally, you will need to stop giving your dog phenylpropanolamine and switch to a different incontinence medication prior to starting selegiline. A dog who is taking both medications concurrently is at an increased risk for developing high blood pressure.

Carefully discussing your dog’s history and medications with your veterinarian will help avoid possible drug interactions and ensure that your dog is a good candidate to use selegiline.

Dog parent hugging her senior Pug, photo

Talk to your veterinarian

When Yoshi’s owner and I discussed selegiline, we decided that Yoshi was a great candidate to try it. Approximately six weeks after Yoshi started selegiline, the owner called me to tell me that Yoshi was sleeping through the night again. His anxiety and pacing also seemed better!

Selegiline can be very beneficial for other senior dogs with CCD, just like it was for Yoshi. However, please talk with your veterinarian to decide if selegiline is right for your dog. Who knows—selegiline might just be the key to improving your dog’s senior years!

Has your dog taken selegiline for CCD?

Please share your experience with it.

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