Zyrtec Clinical Pharmacology

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Zyrtec - Clinical Pharmacology [Certirizine]

In pediatric patients aged 6 to 23 months who received a single dose of 0.25 mg/ kg cetirizine oral solution (mean dose 2.3 mg), the mean Cmax was 390 ng/ mL. Based on cross-study comparisons, the weight-normalized, apparent total body clearance was 304% greater and the elimination half-life was 63% shorter in this pediatric population compared to adults. The average AUC( 0-t) in children 6 months to <2 years of age receiving the maximum dose of cetirizine solution (2.5 mg twice a day) is expected to be two-fold higher than that observed in adults receiving a dose of 10 mg cetirizine tablets once a day.

Geriatric Patients

Following a single, 10-mg oral dose, the elimination half-life was prolonged by 50% and the apparent total body clearance was 40% lower in 16 geriatric subjects with a mean age of 77 years compared to 14 adult subjects with a mean age of 53 years. The decrease in cetirizine clearance in these elderly volunteers may be related to decreased renal function.

Effect of Gender

The effect of gender on cetirizine pharmacokinetics has not been adequately studied.

Effect of Race

No race-related differences in the kinetics of cetirizine have been observed.

Renal Impairment

The kinetics of cetirizine were studied following multiple, oral, 10-mg daily doses of cetirizine for 7 days in 7 normal volunteers (creatinine clearance 89-128 mL/ min), 8 patients with mild renal function impairment (creatinine clearance 42-77 mL/ min) and 7 patients with moderate renal function impairment (creatinine clearance 11-31 mL/ min). The pharmacokinetics of cetirizine were similar in patients with mild impairment and normal volunteers.

Moderately impaired patients had a 3-fold increase in half-life and a 70% decrease in clearance compared to normal volunteers. Patients on hemodialysis (n= 5) given a single, 10-mg dose of cetirizine had a 3-fold increase in half-life and a 70% decrease in clearance compared to normal volunteers. Less than 10% of the administered dose was removed during the single dialysis session. Dosing adjustment is necessary in patients with moderate or severe renal impairment and in patients on dialysis (see DOSAGE AND ADMINISTRATION).