Hydroxyzine

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 (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they 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.
• 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 as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects?

Hydroxyzine may cause the following side effects:

• Sedation
• Excitability
• Tremors
• Dry mouth
• Increased drinking
• Constipation
• Lack of appetite
• Behavioral changes (in cats)

Serious adverse reactions may occur. If any of the following signs develop, stop giving hydroxyzine and contact your veterinarian immediately:

• Difficulty urinating
• Seizures

Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately.  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
• Have heart failure
• Have urinary obstruction
• Have stomach obstruction

USE WITH EXTREME CAUTION in pets that:

• Have seizures
• Are young or old
• Are in their first trimester of pregnancy

USE WITH CAUTION in pets that:

• Have glaucoma
• Have trouble urinating
• Have enlarged prostate
• Have heart disease, liver disease, or kidney disease
• Are in later stages of pregnancy
• Are lactating
• Are working animals

Are there any drug interactions I should be aware of?

Several medications should be used with caution when given with hydroxyzine, including:

• Anticholinergic agents
• Central nervous system (CNS) depressants

This medication can interact with intradermal allergy testing; discontinue this medication at least two weeks prior to testing. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.

Is any monitoring needed with this medication?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

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. Be prepared to provide information about the product and your pet's weight and symptoms.