Hydroxyzine hydrochloride, or Atarax, is an antihistamine approved by the US Food and Drug Administration in 1956 to treat allergies and hives, but it also reduces vomiting, anxiety and pain at some doses. Because hydroxyzine has been available for so long, its side effect profile is well characterized.
Major Side Effect
Extreme drowsiness is the primary side effect of hydroxyzine, possibly because the drug suppresses certain parts of the central nervous system. People taking hydroxyzine should not drive. The sleepiness in most people will stop after a few days of treatment, and it is reversible after stopping the medicine.
Mild Side Effects
Relatively few minor side effects have been noted with hydroxyzine use. These include dry mouth, tremor and other involuntary movements, especially at high doses.
Side Effects in Special Populations
Older patients have more pronounced responses to hydroxyzine and may need to start taking lower doses so that hydroxyzine does not build up in their bodies and cause longer-lasting effects. Patients allergic to hydroxyzine will experience shortness of breath, wheezing and chest tightness.
Overdose Side Effects
During hydroxyzine overdose, excessive sedation is still the most common side effect; however, respiratory depression is also a risk. Convulsions have been reported at higher-than-recommended doses. Vomiting and low blood pressure are possible as well.
Drug Interaction Cautions
Hydroxyzine side effects can be enhanced with the use of other drugs, like phenobarbital or prescription narcotics, that also depress the central nervous system. Side effects of these drug interactions include extreme or prolonged drowsiness and decreased breathing. In addition, hydroxyzine can cause increased alcohol effects when these two chemicals are used together.
Expert Insight
Hydroxyzine hydrochloride is a salt form of the drug hydroxyzine and is formulated as a tablet. Hydroxyzine pamoate, marketed as Vistaril, is another salt form of the same active drug and is formulated as a capsule and liquid. According to the Vistaril prescribing label, the doses of these two formulations are equal to each other.
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