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We represent a community with a shared interest in data analysis using the population approach.

   Paris, France

Retrospective Population Pharmacokinetics Of Cetirizine In Infants And Children

Ziad Hussein (1), Maria Pitsiu (1), Oneeb Majid (1), L. Aarons (2), A. Stockis (3) and M. de Longueville (3)

(1) Medeval Ltd and (2) University of Manchester, Manchester, UK, and (3) UCB Pharma, Braine-l’Alleud, Belgium

This population analysis characterises the pharmacokinetics of cetirizine in infants and children using data pooled from six clinical trials following either single or multiple dose administration for up to 52 weeks. Cetirizine plasma concentration data was used for non-linear mixed effects modelling using the NONMEM program. Data from 112 children, aged 6 months to 12 years, were obtained. A one-compartment open model with first-order absorption and elimination was fitted to the plasma profiles.

The effect of age, weight, body surface area, gender and CLcr on CL/F and V/F was examined.

There were statistically significant associations between CL/F and both age and gender and between V/F and age, given by the following equations:

Male children: CL/F (L/h) = 0.771 + 0.12· AGE

Female children: CL/F (L/h) = 0.592 + 0.12· AGE

Male and Female Children: V/F (L) = 4.00 + 1.42· AGE

No other statistically significantly associations were found. The population estimate of CL/F for an average age of 7 years is 1.61 L/h and 1.43 L/h for male and female children, respectively. The population estimate of V/F is 13.9 L. The %CV of the variance parameters ranged from 21.8% to 37.2%. In conclusion, the current strategy of stratifying the dosage regimen of cetirizine in children by age is justified by the present analysis.