Pharmacokinetics of cetirizine in the elderly and patients with renal insufficiency.

The disposition of cetirizine, a new H1-receptor antagonist, was evaluated in 30 healthy adults of various ages and in 15 adults with various degrees of renal insufficiency. The purpose of the evaluation was to determine whether dosage schedules of cetirizine will require modification in the elderly or patients with renal insufficiency. We found that the elimination half-life of cetirizine was prolonged in patients with mild and moderate renal insufficiency, compared with age-matched individuals with normal renal function (19.0 +/- 3.3 and 20.9 +/- 4.4 hours, vs 7.4 +/- 3.0 hours, respectively). However, the mean apparent steady-state volume of distribution did not differ significantly between these subject groups (range 0.41 to 0.47 L/kg). Total body clearance and renal clearance of the drug were both significantly lower in the patients with renal insufficiency. In elderly subjects, the elimination half-life of cetirizine was significantly prolonged compared with younger adults, and apparent total body clearance was significantly reduced. Again, there was no significant difference in the volume of distribution between the groups. Linear regression showed good correlations between the disposition characteristics of cetirizine and age as well as creatinine clearance. However, we found no relationship between age and the ratio of apparent total body clearance of cetirizine to creatinine clearance. Thus the disposition of cetirizine is independent of age but dependent on renal function. The relationship between apparent total body clearance of cetirizine and creatinine clearance was significant only in patients with creatinine clearances greater than 40 mL/min. Progressive decrements in creatinine clearance were not associated with similar changes in the pharmacokinetic parameters of cetirizine.