PHARMACOKINETICS OF CETIRIZINE IN 2- TO 6-YEAR-OLD CHILDREN

Eight children (3.84 +/- 1.17 years old) received a single oral 5 mg c etirizine dose (0.32 +/- 0.07 mg.kg(-1)) as a 10 mg.ml(-1) solution, 1 .73 (+/- 0.64) hours before a minor surgical intervention (mean durati on +/- SD = 0.90 +/- 0.25 h). Seven venous blood samples were collecte d before administration (t(0)) and 0.5 h, 1.5 h, 4 h, 8 h, 12 h and 24 h after dosing, and urine samples were collected up to 24 hours after the dose. The mean +/- SD kinetic parameters were: peak plasma level (C-max) 607 +/- 231 mu g.l(-1) reached in 1.93 +/- 1.39 h (t(max)), el imination half-life (t(1/2)) 5.55 +/- 0.98 h, area under the plasma co ncentration time curve (AUC(0-infinity)) 4,772.1 +/- 1,318.4 mu g.l(-1 ).h, mean residence time (MRT) 8.13 +/- 1.31 h, apparent plasma cleara nce (Cl/f) 1.27 +/- 0.80 ml.min(-1).kg(-1) apparent volume of distribu tion (Vz/f) 0.60 +/- 0.38 l.kg(-1). Urinary recovery was 38.4 +/- 9.9% (n = 4) of the dose. Renal clearance was 0.42 +/- 0.10 ml.min.kg(-1) (n = 6). No influence of age on the cetirizine parameters was evidence d among this group, except for MRT (p < 0.05) which decreases with age . When compared with results in adults, elimination half-life (tin) wa s twice as short and apparent clearance twice as great. These results suggest that a higher dosage b.i.d. may be required in children.