Hydroxyzine for Dogs

Written by: Dr. Merliza Cabriles, DVM

What is Hydroxyzine for Dogs?

Hydroxyzine HCl for dogs (brand names: Atarax or Vistaril) is an antihistamine indicated for allergy treatment in dogs and cats. While it is not approved by the US-FDA for use in pets, veterinarians generally prescribe (Rx only) it as an extra-label drug. An OTC alternative might be Benadryl for your dog.

In addition to

Allergies
Atopy, and
Dermatitis,

Hydroxyzine is also used to address the following conditions in dogs:

Nausea – hydroxyzine has an antiemetic effect which helps reduce nausea
Anxiety– hydroxyzine has an anxiolytic effect thus it can be used as a tranquilizer or mild sedative

As an antihistamine, hydroxyzine blocks histamine (H1) receptors that are found on small blood vessels and smooth muscles. This will prevent histamine (a chemical that is released in response to inflammation) from attaching to the receptors and causing classical symptoms of allergy such as inflammation, itchiness, breathing difficulties, etc.

Precautions

Be sure to inform your veterinarian about any health problems your dog is suffering from. Hydroxyzine should be used with extreme caution in animals diagnosed with the following conditions:

Allergy to antihistamine or any of its components
Hypertension or high blood pressure
Glaucoma
Lung disease
Prostate enlargement
Heart disease
Bladder-neck obstruction
Pregnancy
Nursing animals
Hypothyroidism
Obstruction of the pyloric juntcion

Interactions With Other Drugs

Your veterinarian should also know about any medications that your pet may be taking.

Precautionary measures should be exercised when hydroxyzine is given with:

CNS-depressant drugs (such as Acepromazine)
Monoamine oxidase inhibitors (MAOIs) (such as Selegiline)
Preventic Tick collars
Medications indicated for wheezing (theophylline, ephedrine, epinephrine)

Interactions may occur when hydroxyzine is used with the following drugs:

Barbiturates
Epinephrine
Tranquilizers
Anticholinergic drugs
Heparin
Warfarin
Vitamins and supplements

Side Effects of Hydroxyzine in Dogs

Since hydroxyzine can cause drowsiness and dizziness, it should not be given to dogs that are working on specific jobs, such as guide dogs, police dogs, bomb-sniffing dogs, etc.

Any sign of an adverse reaction displayed by your pet should be treated as an emergency, one that requires immediate veterinary attention. Important symptoms that you should watch out for include the following:

Swelling of the face, throat, tongue, or lips
Hives
Weakness as a result of low blood pressure
Breathing difficulty
Seizures
Dizziness
Confusion
Dry mouth
Nausea or vomiting
Blurred vision
Drowsiness
Increased urination
Trouble urinating
Over-excitability
Sudden change in behavior

Talk to your veterinarian about anything that seems unusual or bothersome to your pet while he is taking hydroxyzine.

Hydroxyzine Dosage for Dogs

There are two formulations of hydroxyzine being used in dogs. Atarax for dogs has hydroxyzine pamoate as its active ingredient, while it’s hydroxyzine hydrochloride in Vistaril for dogs.

Common preparations for dogs are hydroxyzine 10 mg, 25 mg, and 50 mg tablets.

The standard dosage for dogs is

1 mg/lb bodyweight (2 mg/kg body weight)
given every 6 to 8 hours.

Duration of medication will depend on the dog’s condition and response to treatment. Your veterinarian may advice continued treatment for a certain length of time after the animal shows signs of recovery.

If you happen to miss a dose, give it as soon as you remember. But if it’s almost time for the next dose, skip the missed dose and continue with the regular schedule.

Don’t give two doses at once.