Hydroxyzine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
dry mouth, nose, and throat
upset stomach
drowsiness
dizziness
chest congestion
headache
reddening of skin
If you experience any of the following symptoms, call your doctor immediately:
difficulty breathing
muscle weakness
increased anxiety
Several reactions have been noted in manufacturer guidelines for two forms of hydroxyzine: Atarax and Vistaril. In Atarax, symptoms are similar to those of Vistaril -- deep sleep, incoordination and dizziness have been reported, as in children and adults, as well as others such as hypotension, tinnitus and headaches. Gastro-intestinal effects have also been observed in both Vistaril and Atarax, as well as less serious effects such as dryness of the mouth, constipation caused by antimuscarinic properties of hydroxyzine.
Central nervous system problems such as hallucinations or confusion have been observed in rare cases, attributed mostly to overdosage. Such properties have been attributed to hydroxyzine in several cases, particularly in patients treated for neuropsychological disorders, as well as in cases where overdoses have been observed. While there are reports of the "hallucinogenic" or "hypnotic" properties of hydroxyzine, several clinical data trials have not reported such side effects from the sole consumption of hydroxyzine, but rather, have described its overall calming effect described through the stimulation of areas within the formatio reticularis. The description of hallucinogenic or hypnotic properties have been described as being an additional effect from overall central nervous system suppression by other CNS agents, such as lithium or alcohol.
The effect of hydroxyzine has also been tested on the ability of humans in the registration and storage of memory, and was used in comparison with relatively safe drugs, such as hydroxyzine, to illustrate the effects of benzodiazepines, which are thought to have adverse effects on the capacity of memory storage. Hydroxyzine was found to have no adverse effects on memory in relation to lorazepam, which caused several deficiencies in the capacity of memory storage.
In a comparative study with lorazepam on memory effects, patients who had taken hydroxyzine experienced sedative effects similar to drowsiness, but recalled that they felt capable, attentive and able to continue with a memory test under these conditions. Conversely, those under the effects of lorazepam felt unable to continue due to the fact they felt out of control with its effects; 8 out of 10 patients describing tendencies of problems with balance and control of simple motor functions.
Severe somnolence with or without vivid dreams or nightmares may occur in users with antihistamine sensitivities or other CNS depressants available in their systems. Hydroxyzine exhibits very potent anxiolytic and sedative properties in many psychiatric patients. Other studies have suggested that hydroxyzine acts as an acute hypnotic, reducing sleep onset latency and reciprocal increases in sleep duration -- also showing that some drowsiness did occur, but in female patients who also had greater hypnotic response. It did not, however, show any significant or noticeable effect of drowsiness, other than in female patients' subjective responses.
Some users may report shortness of breath or wheezing, a result of a mild allergic reaction to the medication itself.
In contrast to drugs in the benzodiazepine class, (i.e. alprazolam, diazepam) which carry a potential for abuse and dependence, hydroxyzine is very unlikely to cause any dependence due to its relative strength compared to other substances.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online at http://www.fda.gov/MedWatch/report.htm or by phone 1-800-332-1088.
