indication

For symptomatic relief of anxiety and tension associated with psychoneurosis and as an adjunct in organic disease states in which anxiety is manifested. Useful in the management of pruritus due to allergic conditions such as chronic urticaria.

pharmacology

Hydroxyzine, a piperazine antihistamine structurally related to buclizine, cyclizine, and meclizine, is used to treat histamine-mediated pruritus or pruritus due to allergy, nausea and vomiting, and, in combination with an opiate agonist, anxiolytic pain. Hydroxyzine is also used as a perioperative sedative and anxiolytic and to manage acute alcohol withdrawal. Hydroxyzine's active metabolite, cetirizine, is also used as an H₁-antagonist.

mechanism of action

Hydroxyzine competes with histamine for binding at H₁-receptor sites on the effector cell surface, resulting in suppression of histaminic edema, flare, and pruritus. The sedative properties of hydroxyzine occur at the subcortical level of the CNS. Secondary to its central anticholinergic actions, hydroxyzine may be effective as an antiemetic.

toxicity

Oral, rat LD₅₀: 950 mg/kg. Symptoms of overexposure include hypersedation.

biotransformation

Hepatic

absorption

Rapidly absorbed from the gastrointestinal tract

half life

20 to 25 hours

drug interactions

Butabarbital: Hydroxyzine may enhance the CNS depressant effect of barbiturates like butabarbital. Consider a decrease in the barbiturate dose, as appropriate, when used together with hydroxyzine. With concurrent use, monitor patients closely for excessive response to the combination.

Butalbital: Hydroxyzine may enhance the CNS depressant effect of barbiturates such as butalbital. Consider a decrease in the barbiturate dose, as appropriate, when used together with hydroxyzine. With concurrent use, monitor patients closely for excessive response to the combination.

Donepezil: Possible antagonism of action

Galantamine: Possible antagonism of action

Rivastigmine: Possible antagonism of action

Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Hydroxyzine, may be reduced due to antagonism. The interaction may be beneficial when the anticholinergic action is a side effect. Monitor for decreased efficacy of both agents.

Trimethobenzamide: Trimethobenzamide and Hydroxyzine, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Triprolidine: Triprolidine and Hydroxyzine, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Additive CNS depressant effects may also occur. Monitor for enhanced anticholinergic and CNS depressant effects.

Trospium: Trospium and Hydroxyzine, two anticholinergics, may cause additive anticholinergic effects and enhanced adverse/toxic effects. Monitor for enhanced anticholinergic effects.