Side Effects of Anxiety Medications in Dogs

Written By hannah hollinger
Published: 05/03/2017Updated: 11/13/2021
Veterinary reviewed by Dr. Linda Simon, MVB MRCVS
Side Effects of Anxiety Medications in Dogs - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What are Side Effects of Anxiety Medications?

Anxiety medications are well known in human social circles as a means to reduce stress levels or the anxiousness associated with those stress levels. These types of medications are being sought more often these days for some of the same types of behaviors in canines.  While some work quite well in some animals, some do not and still, others can be dangerous or even fatal for your beloved canine family member.

Side effects can be defined as adverse reactions to a substance.  Anxiety medications are defined as medications given to calm, relax and modify anxiousness in canines.

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Symptoms of Side Effects of Anxiety Medications in Dogs

Anxiety in your dog can be displayed in a number of ways or behaviors.  Here are some examples. Many owners are unaware that they could be anxiety manifestations:

  • Excessive barking or howling
  • Inappropriate elimination (urination and defecation). This doesn’t always mean that housebreaking training didn’t work
  • Chewing or licking, sometimes injuring himself or causing lick granulomas
  • Scratching, digging or other types of destruction
  • Escaping the crate or garden
  • Pacing
  • Defecating followed by consumption of feces
  • Distress at being left alone

Some of the side effects of the anxiety medication can include:

  • Lethargy
  • Irregularities in heart rate
  • Increased levels of anxieties/stress levels
  • Bowel and urinary changes (either increasing or decreasing in frequency, changes in consistency, etc)
  • Vomiting
  • Reduced muscle control
  • Lowered blood pressure
  • Weakness 


The types of side effects of anxiety medications in dogs lie in their medical drug type (classification) which relates to how they control the anxiety issues:

H1 Antagonists

  • These are medications like Benadryl which work well for allergies and may calm your doggy family member thanks to the mild sedative effects
  • Side effects include drowsiness, fatigue, urinary retention, delayed reaction and dry mouth


  • These medications (Valium, Xanax and Ativan) have an enhancing effect on some neurotransmitters 
  • Side effects include drowsiness, loss of coordination, changes in appetite and sedation


  • These drugs (Fluoxetine or Paxil) have an effect on the reuptake of serotonin 
  • Side effects include vomiting, diarrhea, fatigue and panting

Causes of Side Effects of Anxiety Medications in Dogs

Causes of side effects of anxiety medications in dogs stem from several sources:

  • Undiagnosed or underlying pre-existing health conditions or disease
  • Dosing deviations or miscalculations of required dosage
  • Diagnosed heart, liver or lung disease reacting with the anxiety medication given
  • Serotonin syndrome - This is a specific condition that occurs when a medication is used that causes the levels of natural occurring serotonin to build up in the body of the host
  • Keep in mind, sometimes there is no obvious cause and a dog will develop adverse reactions

Causes of anxiety in your beloved pet also emanates from several sources:

  • Separation anxiety - This is the most commonly found anxiety trigger in most domesticated dogs and cats
  • Situational anxiety 
  • Thunderstorm phobia
  • Noise phobia e.g. to fireworks
  • Fear-based aggressions

Diagnosis of Side Effects of Anxiety Medications in Dogs

When your veterinary professional gets involved in the diagnosing process for the anxious behaviors of your family pet, he will need some valuable input from you.  Your complete history will, in this case, need not only the inclusion of the usual dietary habits and activity levels of the patient, but also the behaviors that you’re noticing in your companion.  He will need to know the frequency of each of the symptoms/behaviors you’ve noticed as well as the duration of each symptom/behavior.  He will also likely want some correlation to specific circumstances which seem to trigger the behavior such as thunderstorms, loud noises, being left alone, and strangers coming into the house. 

Your veterinary professional will do a physical examination and will likely need to get blood samples for lab evaluation.  He will be looking to see if the normal blood chemistry values are out of line in any area, suggesting that something may be changing the way the various systems in the canine body do their jobs.  Serotonin and cortisol are two areas of particular interest in the interpretation of these tests. Serotonin levels really can’t be measured like red and white blood cell counts can, for example, but can be assessed based on other clinical findings, checking the function of the systems which are affected by serotonin, history of health, behaviors and medications being used as well as ruling out of other possibilities.

Treatment of Side Effects of Anxiety Medications in Dogs

Treatment of the side effects of anxiety medication in dogs can be multi-leveled, depending on the side effects and the cause of the anxiety and can be utilized alone or in any combination:

  • Dosage adjustments - Some medications work better in some dogs than others and dosage changes may be required to find the best amount to use, especially as, with time, the tolerance and efficacy of the drug can change
  • Trying other medications as alternatives or in conjunction with the anxiety medication causing the side effects, especially as the side effects may include heart arrhythmias or liver problems
  • Complete discontinuance of synthetic medications for anxiety in lieu of more natural remedies

We may be able to reduce the dose of medicine or stop it completely once the right behavioural modifications and training program has begun

  • Behavior training or retraining of either the canine or the family of the canine - this can include things like changing the timing of your attention-giving activities like petting, grooming and playing with your doggy family member so that he is ready for a nap when you have to leave him alone,or taking him for a long walk before you leave (again helping him to be ready to rest), or offering him a favored toy just before you leave. These activity changes can reduce the abruptness of your departure and lessen the separation anxiety and fear felt by your canine family member
  • Other behavioral techniques which may ultimately help in a more natural and safe manner of management of the anxiety behaviors
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Recovery of Side Effects of Anxiety Medications in Dogs

For some canines, behavior modifications for the pet, as well as the favored family members, can help to assuage the anxiety behaviors being exhibited by your pet.  But, for those canines in which these various behavior changes or modifications aren’t successful at managing the anxiety in your pet, drugs may be the answer.  It is absolutely not a good idea to venture down the medication road alone.  You need to utilize the expertise and training of a reliable veterinary professional for guidance and the administration of these medications.  

Just as one would not venture down this road alone for a human family member without the aid and direction of the family doctor, one should also not do so for the beloved canine family member.  Your veterinary professional can work with you to find just the right regimen to manage the anxiety behaviors in your pet to avoid the side effects of anxiety medications in dogs.

If the drug is causing unacceptable side effects, your vet will work with you to come up with a solution. This may mean altering the dose given, offering a different medicine or prescribing drugs to give alongside the anxiolytic.

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