Mechanism of Action
Description: Hydroxyzine, a piperazine derivative, blocks histamine H1-receptors on effector cells of the GI tract, blood vessels and resp. It is a sedating antihistamine w/ antimuscarinic and significant sedative properties. It also possesses skeletal muscle relaxing, bronchodilator, antiemetic and analgesic properties.
Onset: Oral: 15-30 min. Inj: Rapid.
Duration: Decreased histamine-induced wheal and flare areas: 2 to ≥36 hr. Suppression of pruritus: 1-12 hr.
Pharmacokinetics:
Absorption: Absorbed rapidly from the GI tract. Time to peak plasma concentration: Approx 2 hr.
Distribution: Volume of distribution: Approx 16 L/kg.
Metabolism: Converted in the liver to its active carboxylic acid metabolite (cetirizine).
Excretion: Elimination half-life: Approx 20 hr.