When allergies affect dogs, their immune system quickly responds by releasing a chemical known as histamine. Once released in the body, this chemical triggers an inflammatory response causing all the visible swelling, itchiness and other symptoms typically associated with an allergic reaction. One of the best ways to fight such response is to use specific antihistamines. Hydroxyzine is an effective antihistamine medication, commonly used ''off label'' in veterinary medicine to treat allergic conditions in dogs.
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Identification
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Hydroxyzine, also commonly known by the brand name Atarax, is an antihistamine drug obtained by prescription from a veterinarian. It is generally prescribed to treat allergic symptoms such as itching, atopy and dermatitis in dogs. While the Food and Drug Administration does not currently approve this medication for use in animals, veterinarians often prescribe it legally as an extra-label drug. Hydroxyzine is available in tablet forms of different strengths, as oral syrup or as an injectable concentration.
Function
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When a dog's body releases histamine as a response to allergy, it attaches to specific receptors. Typically, two types of histamine receptors can be found: H1 and H2. When histamine attaches to H1 receptors, which affect small blood vessels and smooth muscles, tissue swelling and itchiness may occur, as well as breathing difficulties. When histamine attaches to H2 receptors, this causes instead a raise in heart rate and in the production of stomach acid. Hydroxyzine mainly works by inhibiting the effect of histamine on the H1 receptors, therefore significantly reducing swelling and itchiness.
Dosage
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Hydroxyzine tablets commonly come in 10 mg, 25 mg, 50 mg and 100 mg strength tablets. The general dose for dogs is 1 mg per pound of body weight given by mouth two to three times daily, according to Dr. Dawn Ruben in PetPlace.com. Duration of therapy varies depending on the condition being treated, the dog's response to treatment and the development of any adverse effects. Hydroxyzine should be administered to the dog as prescribed and always under the guidance and professional advice of a licensed veterinarian.
Warning
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As with any medication, Hydroxyzine can cause a series of side effects in dogs. The most commonly observed are sedation, lethargy, upset stomach with vomiting and diarrhea, and loss of appetite. Dogs suffering from glaucoma, lung or heart disease, prostate enlargement or high blood pressure, should not take this medication. Dogs with known allergies or hypersensitivity to Hydroxyzine should avoid this drug. Hydroxyzine is also known to likely interact with barbiturates, tranquilizers and epinephrine drugs.
Effectiveness
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Typically, Hydroxyzine is well absorbed by the dog's body and takes an average of 20 to 45 minutes in order to start making an effect. Generally, a drug as Hydroxyzine should be given in a 7- to 10-day time frame to judge effectiveness before trying another antihistamine. Success rates vary from dog to dog, and, generally, the use of antihistamines alone is capable of providing itching relief in about 20 to 40 percent of dogs. In many cases, Hydroxyzine may need to be combined with a corticosteroid drug. Hydroxyzine is generally effective in dogs for a time frame of about six to eight hours, according to Barbara Forney, VMD, on the Wedgewood Pharmacy website.
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