By Rania Gollakner, BS, DVM, MPH

What is hydroxyzine?

Hydroxyzine (brand names: Atarax®, Vistaril®, Masmoran®, Multipax®) is an antihistamine used to treat allergic and itchy conditions or as a sedative/tranquilizer.

Its use in cats, dogs, ferrets, horses, and birds to treat itchiness is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is hydroxyzine given?

Hydroxyzine is given by mouth in the form of a tablet, liquid solution, or capsule. It may also be given as an injection in the hospital setting. It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. Measure liquid forms carefully. Hydroxyzine works best when it is given on a regular basis, prior to exposure to an allergen. Do not give this medication within two weeks of intradermal allergy testing. Do not give combination products; use products that contain hydroxyzine as the only active ingredient.

This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effect is sedation. Other side effects may include excitability, tremors, dry mouth and increased drinking, constipation, or lack of appetite. Cats may exhibit behavioral changes. Severe side effects include difficulty urinating or seizures.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Do not use hydroxyzine in pets that are allergic to it or cetirizine, or pets that have heart failure, urinary obstruction, or stomach obstruction. Hydroxyzine should be used with extreme caution in pets with seizures, in young or old animals, or in pets in their first trimester in pregnancy. Use cautiously in pets that have glaucoma, trouble urinating, enlarged prostate, heart disease, liver disease, or kidney disease. It should be used cautiously in pets later in pregnancy, lactating pets, or working animals.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with hydroxyzine: anticholinergic agents, CNS depressants, or epinephrine.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

This medication can also interact with intradermal allergy testing; discontinue this medication at least two weeks prior to testing.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor for serious side effects.

How do I store hydroxyzine?

Store this medication at room temperature and protect from light. Do not freeze the liquid formulations.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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