Absorption Rapidly absorbed. T max is about 1 h. C max is 311 ng/mL.
Food T max is delayed 1.7 h, and C max is decreased 23%.
Distribution 93% protein bound.
Metabolism Cetirizine has a low degree of first-pass metabolism. It also is metabolized by oxidative O-dealkylation to an inactive metabolite.
Elimination 70% is excreted in the urine (50% as unchanged drug) and 10% in the feces. The elimination half-life is 8.3 h. Cl is about 53 mL/min.
Onset 20 to 60 min.
Duration At least 24 h.
Special Populations Renal Function Impairment Moderate impairment (CrCl 11 to 31 mL/min) The half-life is increased 3-fold, and Cl is decreased 70%. Dosage adjustment is recommended in those with moderate or severe impairment.
Hepatic Function Impairment The half-life is increased 50%, and Cl is decreased 40%. Dosage adjustment is recommended.
Elderly The half-life is prolonged 50%, and Cl is 40% lower. Dosage adjustment is recommended.
Children Cl is increased, and half-life is decreased.
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