indication

For the relief of symptoms associated with seasonal allergic rhinitis, perennial allergic rhinitis and the treatment of the uncomplicated skin manifestations of chronic idiopathic urticaria

pharmacology

Cetirizine, the active metabolite of the piperazine H₁-receptor antagonist hydroxyzine, is used to treat chronic idiopathic urticaria, perennial allergic rhinitis, seasonal allergic rhinitis, allergic asthma, physical urticaria, and atopic dermatitis.

mechanism of action

Cetirizine competes with histamine for binding at H₁-receptor sites on the effector cell surface, resulting in suppression of histaminic edema, flare, and pruritus. The low incidence of sedation can be attributed to reduced penetration of cetirizine into the CNS as a result of the less lipophilic carboxyl group on the ethylamine side chain.

toxicity

Somnolence (sleepiness or unusual drowsiness), restlessness, irritability

absorption

mean peak plasma concentration (Cmax) of 114 ng/mL at a time (Tmax) of 2.2 hours postdose was observed for cetirizine

half life

8.3 hours