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Hydroxyzine for Dogs: Uses and Side Effects

Hydroxyzine for Dogs: Uses and Side Effects

Hydroxyzine is a common antihistamine used for dogs. This DogAppy article will tell you how to use hydroxyzine for dogs, its various applications, and the side effects you need to look out for.
Akshay Chavan
A Note of Caution:
Hydroxyzine is not an FDA-approved drug for use in veterinary medicine, but is legally prescribed by veterinarians for dogs and cats.
Hydroxyzine is an antihistamine drug that reduces allergic symptoms such as hives, atopy, and dermatitis, both in humans and pets like dogs and cats. This drug is known by several other names, like Atarax, Hydroxyzine HCL, Hydroxyzine pamoate, and Vistaril.

Whenever an allergen such as pollen grains or dust particles enters the body, the immune system kicks into action and secretes chemicals called histamines. These histamines travel to the blood vessels, smooth muscles, respiratory tract, and heart, and get attached to certain structures called 'histamine-receptors' located on the cells. This causes the blood vessels to widen and become more porous, leading to the fluid leaking from the vessels into the tissue. This is the common reason why histamines cause a runny nose and teary eyes. Histamine also affects nerves, causing an itchy sensation in the skin and eyes. Antihistamines are chemicals that block the histamine receptors or the histamines and reduce the itchy sensation caused during allergic reactions.

Normally, there are two types of histamine receptors: H1 and H2 receptors. While attachment of histamines to H1 causes allergic symptoms such as itching and runny nose, the H2 receptors modify the heart rate and rate of breathing. Hydroxyzine is called a H1 antagonist, which means that it acts by blocking the attachment of histamine molecules to the H1 receptors. Hydroxyzine does not affect the H2 receptors, which is why its uptake does not influence heart rate and breathing. So basically what happens is, when substances like pollen grains come in contact with the body, it mistakes them to be harmful substances, and initiates an allergic response to them. Using hydroxyzine for dogs will alleviate these allergic symptoms.


✔ Remedy for allergic reactions like hives (utricaria), itching, and rashes
✔ Given as a sedative for anxious dogs
✔ Remedy for allergic reactions to
  • snakebites
  • vaccination
  • blood transfusion
  • insect stings
  • inhaled allergens
✔ To treat motion sickness due to its anti-nausea effect
✔ To be given in combination with corticosteroids, when hydroxyzine alone doesn't work

Side Effects
  • Sedation
  • Drowsiness and dizziness
  • Depression
  • General lethargy
  • Anxiety
  • Coordination problems
  • Fine/whole body tremors
  • Weakness
  • Overly excited behavior
  • Dehydration
  • Blurred vision
  • Dry mouth
  • Diarrhea
  • Nausea
  • Vomiting
  • Vision problems
  • Confusion
  • Loss of appetite
Contact the vet immediately if you see any of the following symptoms in your dog:
  • Difficulty in breathing
  • Swollen facial muscles
  • Seizures
  • Swollen lips, tongue or throat

Hydroxyzine is available in tablets, capsules, syrups, and injectable formulations. In tablet form, it comes in 10 mg, 25 mg, 50 mg, and 100 mg concentrations. Capsules come in 25 mg, 50 mg, and 100 mg formulations. The drug is available in 25 mg/ml and 50 mg/ml injectable concentrations.

The standard dosage for dogs is 1 mg per pound of body weight, that should be administered 2 - 3 times a day at intervals of 8 - 12 hours. It is generally given orally with or without food. It is advisable not to skip doses and continue administering the drug even when the dog shows signs of recovery. In case you skip a dose, administer it as fast as possible, and only give the next one when it's time for the next dose. Never give your dog two doses of hydroxyzine at once.

  • Should not be used in animals with intestinal blockages, enlarged prostate, severe heart illness, liver or kidney disease, or bladder obstruction.
  • Should not be given to pregnant and lactating mothers.
  • Should be used with caution if the dog is a working animal, due to its effect of sedation.
  • Should not be used in animals with previous history of seizures.
  • Consult your veterinarian if you give your dog any of the following drugs: chlorpheniramine, meperidine, amitriptyline, fluoxetine, acepromazine.
Always consult a veterinarian before you begin giving hydroxyzine to your dog, or if you see any of the adverse side effects mentioned above. Though it is a relatively safe drug for pets, if not given under proper conditions, it can be extremely harmful, even causing death in rare cases.