Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: hydroxyzine

BRAND NAMES: Atarax; Vistaril

DRUG CLASS AND MECHANISM: Hydroxyzine is an antihistamine with anticholinergic (drying) and sedative properties that is used to treat allergic reactions. The body releases histamine during several types of allergic reactions and--to a lesser extent--during some viral infections, such as the common cold. When histamine binds to its receptors on cells, it causes the cells to release chemical messengers that lead to sneezing, itching, and increased mucus production. Antihistamines, like histamine, binds to the histamine receptors, but when they bind to the receptors they do not stimulate the cells to release chemical messengers. In addition, they prevent histamine from binding and stimulating the cells. Hydroxyzine itself has no activity. After ingestion, it is converted to its active form. The active form of hydroxyzine is a drug called cetirizine (Zyrtec). Although, both hydroxyzine and cetirizine act as antihistamines, hydroxyzine causes more sedation than cetirizine. The FDA approved hydroxyzine in 1956.

GENERIC AVAILABLE: Yes

PRESCRIPTION: Yes

PREPARATIONS: Tablets: 10, 25, and 50 mg. Capsules: 25, 50, and 100 mg. Syrup: 10 mg per teaspoonful (5mL). Suspension: 25 mg per teaspoonful (5mL). Injection: 25 and 50 mg/ml

STORAGE: Capsules, tablets, and liquids should be stored at room temperature 15-30°C (59-86°F). Liquid should not be frozen and should be shaken well prior to each use. Injectable hydroxyzine should be stored below 30°C (86°F).

PRESCRIBED FOR: Hydroxyzine is used for the relief of pruritus (itching) caused by various allergic conditions. Hydroxyzine is also used for treating anxiety and tension, and inducing sedation prior to or after anesthesia.

DOSING: Hydroxyzine has its maximal effect about 30 to 60 minutes after it is taken. Its effects last for 4 to 6 hours. The recommended dose for treating pruritus is 25 mg given 3 or 4 times daily. When used for sedation, the recommended dose is 50 to 100 mg. Anxiety and tension are managed with 50 to 100 mg 4 times daily. Hydroxyzine can be taken with or without food.

DRUG INTERACTIONS: Hydroxyzine adds to (exaggerates) the sedating effects of alcohol and other drugs that can cause sedation such as the benzodiazepine class of anti-anxiety drugs [for example, diazepam (Valium), lorazepam (Ativan), clonazepam (Klonopin), alprazolam (Xanax)], the narcotic class of pain medications and its derivatives [for example, oxycodone and acetaminophen (Percocet), hydrocodone/acetaminophen (Vicodin), guaifenesin (Dilaudid), Codeine, propoxyphene (Darvon)], the tricyclic class of antidepressants [for example, amitriptyline (Elavil), imipramine (Tofranil), desipramine (Norpramin)], and certain antihypertensive medications [for example, clonidine (Catapres), propranolol (Inderal)]. Hydroxyzine can also intensify the drying effects of other medications with anticholinergic properties [for example, dicyclomine (Bentyl), bethanechol (Urecholine), Probanthine, amitriptyline (Elavil), chlorpromazine (Thorazine)]. When using these drugs, the dose of hydroxyzine may require reduction, therefore.

PREGNANCY: A limited number of studies of hydroxyzine in pregnant women suggests that there may be a relationship between its use in the first trimester of pregnancy and congenital abnormalities in the fetus. Therefore, hydroxyzine should be avoided during the first trimester of pregnancy.

NURSING MOTHERS: It is not known if hydroxyzine is excreted into breast milk. In general, antihistamines are not recommended for use during breastfeeding because they can cause stimulation or seizures in newborns.

SIDE EFFECTS: Hydroxyzine can commonly cause sedation, tiredness, sleepiness, dizziness, disturbed coordination, drying and thickening of oral and other respiratory secretions, and stomach distress. Hydroxyzine may also cause confusion, nervousness, irritability, blurred vision, double vision, tremor, loss or appetite, or nausea. Hydroxyzine should be used with caution (if at all) in persons with narrow-angle glaucoma, prostatic hypertrophy (enlarged prostate gland), hyperthyroidism, cardiovascular disease, hypertension, and asthma.

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