Hydroxyzine is an antihistamine in the piperazine class. It's used to treat a variety of inflammatory canine conditions, including known allergies and allergic skin disease, in which the specific allergen is unknown. It's considered fairly effective in dogs with a low risk of side effects and is available only by prescription.
Histamine is a reactive chemical generated by the body as part of the immune response. Unfortunately, in certain situations, such as as allergies, histamine reactions cause more trouble than the problem they're responding to. Hydroxyzine is one of the first drugs your vet will prescribe if your dog is suffering from an allergic reaction or suspected allergic skin disease. It decreases swelling and relieves itchiness by blocking the body's uptake of histamine. Hydroxyzine can also relieve nausea. Some forms have mild tranquilizing effects.
Potential Side Effects
Hydroxyzine hydrochloride and hydroxyzine pamoate are available under the brand names Atarax, Vistaril, Orgatrax and Hypam. Potential side effects of these include drowsiness, disorientation and lethargy. Cetirizine, brand name Zyrtec, is a form of hydroxyzine that does not cross from the blood into the brain, so it typically avoids these side effects. Side effects of all forms may include dry mouth combined with difficulty urinating, tremors and seizures.
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