Hydroxyzine: uses, side effects and what to know

Hydroxyzine is a first-generation antihistamine, one of the older antihistamines that cause more drowsiness than modern ones, per the NIH. It is taken by mouth as tablets or syrup (hydroxyzine hydrochloride) or as capsules (hydroxyzine pamoate). Atarax and Vistaril are brand names; per MedlinePlus, Atarax is no longer on the market, and hydroxyzine is sold mostly as a generic.

It is a prescription medicine. Per its FDA label, hydroxyzine is chemically unrelated to the benzodiazepines, and the label does not classify it as a controlled substance: it is not a controlled substance.

According to the FDA label, hydroxyzine is approved for three uses:

Hydroxyzine blocks the action of histamine, the substance in the body that causes allergy symptoms such as itching. Per MedlinePlus, it also decreases activity in the brain, and the FDA label explains that its calming effect seems to come from reducing activity in certain deep regions of the brain. It is absorbed quickly: per the label, its effects are usually noticed 15 to 30 minutes after taking it.

The FDA label approves hydroxyzine for relief of the symptoms of anxiety and tension. In other words, it eases symptoms while it acts; it is not a long-term treatment like the antidepressants used for anxiety disorders, for example sertraline. The label also states that its effectiveness for anxiety beyond 4 months has not been assessed in systematic clinical studies, and that the physician should periodically reassess whether it is still helping.

Hydroxyzine is not a benzodiazepine and not a controlled substance. Another medicine used for anxiety that is also not controlled is buspirone. If what you feel is nervousness, worry or panic attacks, read our page on anxiety, which covers symptoms and treatment options, or see mental health care by video.

Per the FDA label, hydroxyzine treats itching caused by allergic conditions: chronic hives (welts that keep coming back for weeks), atopic dermatitis (eczema) and contact dermatitis, and other histamine-driven itching. Because it causes drowsiness, it is sometimes used at night when itching keeps you awake. If the itch is new or you do not know the cause, read about itchy skin: the doctor looks for the cause first.

Hydroxyzine causes drowsiness, which is why some people use it for sleep. But insomnia is not one of its approved uses on the FDA label: taking it only for sleep is an off-label use. Also, per the label, the drowsiness it causes is usually temporary and may fade after a few days of use.

If your main problem is that you cannot sleep, read our page on insomnia.

Label doses for adults: for anxiety, 50 to 100 mg four times a day; for itching, 25 mg three or four times a day; as a sedative around anesthesia, 50 to 100 mg. For children, the label gives different doses by age and weight. For older adults, the label advises starting low.

The doctor decides the dose based on your age, health and other medicines, and adjusts it based on how you respond. Do not change it on your own. MedlinePlus says that if you miss a dose, take it when you remember; but if it is almost time for the next dose, skip the missed one. Do not take a double dose to make up for it.

Per the FDA label, its side effects are usually mild and temporary. The most common are:

The hydroxyzine label has no boxed warning, but it does carry these important warnings:

Heart rhythm (long QT). Cases of QT prolongation and torsade de pointes, a dangerous heart rhythm, have been reported. Most occurred in people with other risk factors: heart disease, electrolyte problems (such as low potassium or magnesium), congenital or family long QT, a recent heart attack, heart failure, a slow heartbeat, or use of other medicines that prolong the QT interval.

Serious skin reaction (AGEP). Rarely, it causes acute generalized exanthematous pustulosis: fever with many small pustules on red, swollen skin. If you get a rash or a skin problem gets worse, stop taking it and seek care.

Older adults. Per the label, sedating medicines can cause confusion and over-sedation in older adults. MedlinePlus says people aged 65 or older usually should not take it, because other medicines are safer for the same conditions.

Overdose. It can cause heavy sedation, seizures and heart rhythm problems. Call Poison Control at 1-800-222-1222 or 911.

Do not take it if you are allergic to hydroxyzine, cetirizine or levocetirizine, if you have a prolonged QT interval, or in early pregnancy, per the FDA label.

Alcohol and other sedatives. Hydroxyzine adds to the effect of other central nervous system depressants: opioids (narcotics), barbiturates, other pain relievers and other sedatives. The label warns that the effects of alcohol may be increased, and MedlinePlus explains that alcohol can make its side effects worse.

Medicines that prolong the QT interval. Caution is needed with antiarrhythmics such as amiodarone or sotalol, some antipsychotics such as quetiapine, some antidepressants such as citalopram or fluoxetine, antibiotics such as azithromycin, erythromycin or clarithromycin, and others such as methadone or ondansetron. Tell the doctor every medicine and supplement you take.

Per the FDA label, hydroxyzine is not used in early pregnancy, because it caused fetal abnormalities in animals at high doses and human data are inadequate. MedlinePlus says not to take it if you are pregnant and to call your doctor right away if you become pregnant while taking it. It is also not recommended while breastfeeding: the label says it should not be given to nursing mothers. If you are pregnant, planning a pregnancy or breastfeeding, tell the doctor.

Cetirizine (Zyrtec) is a metabolite of hydroxyzine: it is the substance the body turns part of the hydroxyzine into, per the FDA label for cetirizine. Both are antihistamines, but cetirizine is newer and, per MedlinePlus, is one of the antihistamines that cause less sleepiness.

That is why cetirizine is used more for everyday allergies, while hydroxyzine, which is more sedating, also has approved uses for anxiety and sedation. If you had an allergic reaction or AGEP with hydroxyzine, cetirizine and levocetirizine are avoided because of the risk of cross-reaction.