Drug information of Hydroxyzine


Drug group:

Hydroxyzine is a first-generation antihistamine; piperazine-derivative. Hydroxyzine is used as a sedative to treat anxiety. Hydroxyzine is also used to treat allergic skin reactions such as hives or contact dermatitis

Mechanism of effect

Sedative and tranquilizing effects result principally from suppression of activity at subcortical levels of the CNS. Antispasmodic activity apparently mediated through interference with the mechanism that responds to spasmogenic agents such as acetylcholine, histamine, and serotonin. Secondary to its central anticholinergic actions, hydroxyzine may be effective as an antiemetic.


Exhibits antihistaminic, CNS depressant, anticholinergic, antispasmodic, local anesthetic activity, analgesic, sedative and antiemetic activity. Also exhibits primary skeletal muscle relaxant activity.


Rapidly absorbed following oral administration. Onset of sedative action is 15–30 minutes following oral administration. Sedative effect persists for 4–6 hours following single dose.

 Widely distributed into most body tissues and fluids in animals. Not known whether hydroxyzine crosses the placenta or is distributed into milk. Exact metabolic fate not clearly established; appears to be completely metabolized, principally in the liver. Carboxylic acid metabolite is cetirizine, a long-acting antihistamine. Excreted in feces via biliary elimination. Half-life is 20 hours.


Usual Adult Dose for Anxiety

-Oral: 50 to 100 mg 4 times a day
-IM: 50 to 100 mg immediately, then every 4 to 6 hours as needed.

Usual Adult Dose for Pruritus

Oral: 25 mg 3 or 4 times a day.

Usual Adult Dose for Sedation

-Oral: 50 to 100 mg orally
-IM: 25 to 100 mg.

Usual Adult Dose for Nausea/Vomiting

IM: 25 to 100 mg

Usual Pediatric Dose for Sedation

-Oral: 0.6 mg/kg
-IM: 0.5 mg/lb of body weight.

Usual Pediatric Dose for Anxiety

Under Age 6:
Oral: 50 mg/day in divided doses

Age 6 and Over:
Oral: 50 to 100 mg per day in divided doses

Usual Pediatric Dose for Pruritus

Under Age 6:
Oral: 50 mg/day in divided doses

Age 6 and Over:
Oral: 50 to 100 mg per day in divided doses

Usual Pediatric Dose for Nausea/Vomiting

IM: 0.5 mg/lb of body weight.


Local Effects: Possible marked local discomfort, sterile abscesses, erythema, local irritation, and tissue necrosis at injection site; extravasation may cause marked localized sub-Q tissue induration. Phlebitis and hemolysis reported following IV administration.

Hydroxyzine may rarely cause acute generalized exanthematous pustulosis (AGEP), a serious skin reaction characterized by fever and numerous small, superficial, non-follicular, sterile pustules, arising within large areas of edematous erythema.

 Inform patients about the signs of AGEP, and discontinue Hydroxyzine at the first appearance of a skin rash, worsening of pre-existing skin reactions which Hydroxyzine may be used to treat, or any other sign of hypersensitivity.

Points of recommendation

You should not use hydroxyzine if you are allergic to it, or if:

  • you have long QT syndrome;
  • you are allergic to cetirizine (Zyrtec) or levocetirizine (Xyzal); or
  • you are in the first trimester of pregnancy.

You should not use hydroxyzine if you are pregnant, especially during the first or second trimester. Hydroxyzine could harm the unborn baby or cause birth defects. Use effective birth control to prevent pregnancy while you are using this medicine.

Possible drowsiness; performance of activities requiring mental alertness or physical coordination may be impaired.

Concurrent use of other CNS depressants may potentiate CNS depression.

To make sure this medicine is safe for you, tell your doctor if you have:

  • blockage in your digestive tract (stomach or intestines);
  • bladder obstruction or other urination problems;
  • glaucoma;
  • heart disease, slow heartbeats;
  • personal or family history of long QT syndrome;
  • an electrolyte imbalance (such as high or low levels of potassium in your blood);
  • if you have recently had a heart attack.

It is not known whether hydroxyzine passes into breast milk or if it could harm a nursing baby. You should not breast-feed while using this medicine.

Do not give this medicine to a child without medical advice.

Hydroxyzine is for short-term use only.

You should not take this medicine for longer than 4 months.

Pregnancy level


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