Hydroxyzine Pamoate Side Effects
Hydroxyzine is a first-generation antihistamine, available as both hydroxyzine hydrochloride and hydroxyzine pamoate. These differing chemical forms, or "salt" forms, affect drug absorption in the body. Though various salt forms may be absorbed at differing rates, the end result is the same active ingredient, in this case, hydroxyzine.
Hydroxyzine may be used in the treatment of anxiety, itching and nausea. Hydroxyzine may also be given as a sedative, and is available in a variety of dosage forms, including oral suspension and syrup, tablets, injection and capsules. Common trade names include Atarax (hydrocholoride form) and Vistaril (pamoate form), among others.
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History
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Histamine-blocking compounds were first discovered in the late 1930s, but were proven too toxic for continued use. By the mid 1940s, however, safer compounds were derived. These older, or "first-generation," antihistamines were well known for causing drowsiness and sedation. As antihistamine development continued, less sedating, "second-generation" agents became available.
Mechanism of Action
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Hydroxyzine counteracts the effects of histamine, a natural compound involved in the body's immune and fight-or-flight responses. Histamine release may be increased during stress or allergic reaction, and may cause itching, rash, breathing difficulties, nausea and anxiety. Hydroxyzine acts to block such effects. In doing so, hydroxyzine crosses from the blood stream into the brain, where it may cause sedation, the most common side effect.
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Side Effects
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Other common central nervous system effects include headache, fatigue and dizziness. Hydroxyzine may also cause dry mouth, blurred vision and thickened mucosal secretion. At higher than recommended doses, seizures, low blood pressure and over-sedation may occur.
Precautions
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Hydroxyzine may be confused with hydralazine, a separate drug used to treat high blood pressure. Patients should verify with both physician and pharmacist which drug is intended.
Considerations
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Hydroxyzine injection is typically given intramuscularly, into a large muscle such as the gluteus or deltoid. The manufacturer discourages intravenous administration, due to potentially serious effects on veins and blood pressure.
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