Hydroxyzine (Atarax®, Anxanil®, Vistaril®) for Dogs and Cats

Overview of Hydroxyzine for Dogs and Cats

• Hydroxyzine, known as Atarax®, Anxanil®, Vistaril® is used primarily to treat allergic symptoms, itching, and dermatitis for dogs and cats.
• Histamine is a chemical that is released in the body in response to inflammation or allergy. This chemical travels throughout the body searching for specific histamine receptors (targets on cells). Once attached to the receptors, histamine will cause swelling, itchiness and other symptoms associated with an allergic response.
• There are two types of histamine receptors: H1 and H2. H1 receptors affect small blood vessels and smooth muscles. When histamine attaches to the H1 receptors, the small blood vessels dilate and fluid begins to leak out. This results in tissue swelling and itchiness. In addition, the smooth muscles lining the small airways constrict, causing tightness and some breathing difficulty. H2 receptors affect heart rate and stomach acid secretions. When histamine attaches to H2 receptors, the heart rate increases and stomach acid secretions are increased, potentially raising the risk of developing ulcers.
• Drugs that block the effects of histamine are called antihistamines. There are a number of drugs demonstrating antihistamine effects; some are useful in allergies, others for preventing excessive stomach acid. The effects of the antihistamine depend on whether it binds with the H1 receptors or H2 receptors. There are few drugs that affect both types of receptors.
• Hydroxyzine is one type of antihistamine that inhibits the action of histamine, particularly its effect on H1 receptors. This results in a reduction or prevention of swelling and itchiness. Hydroxyzine has little to no effect on heart rate or stomach acid secretions.
• Hydroxyzine is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
• This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names of Hydroxyzine

• This drug is registered for use in humans only.
• Human formulations: Atarax® (Roerig), Anxanil® (Econo Med), Vistaril® (Pfizer) and various generic preparations
• Veterinary formulations: None

Uses of Hydroxyzine for Dogs and Cats

• Hydroxyzine is used primarily to treat allergic symptoms, itching, and dermatitis. It is commonly used in the treatment of atopy.

Precautions and Side Effects

• While generally safe and effective when prescribed by a veterinarian, hydroxyzine can cause side effects in some animals.
• Hydroxyzine should not be used in animals with known hypersensitivity or allergy to the drug.
• Animals with glaucoma, lung disease, heart disease, high blood pressure and prostate enlargement should not take hydroxyzine.
• Hydroxyzine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with hydroxyzine. Such drugs include barbiturates, tranquilizers and epinephrine.
• The most common adverse effects of hydroxyzine are sedation, lethargy, vomiting, diarrhea and lack of appetite.

How Hydroxyzine Is Supplied

• Hydroxyzine is available in 10 mg, 25 mg, 50 mg and 100 mg tablets.
• Hydroxyzine 2 mg/ml oral syrup is also available.
• Hydroxyzine 25 mg/ml and 50 mg/ml injectable concentration is also available.

Dosing Information of Hydroxyzine for Dogs and Cats

• Medication should never be administered without first consulting your veterinarian.
• Hydroxyzine is dosed in dogs at 1 mg per pound (2 mg/kg) PO two to three times daily.
• In cats, hydroxyzine is dosed at 0.5 to 1 mg per pound (1 to 2 mg/kg) or 5 to 10 mg per cat PO every 8 to 12 hours.
• The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.