Cetirizine and Levocetirizine Use in Children

Marcia L. Buck, Pharm.D., FCCP, FPPAG

Disclosures

Pediatr Pharm. 2010;16(6) 

In This Article

Pharmacokinetics

Both cetirizine and levocetirizine are rapidly and extensively absorbed after oral administration. The average time to maximum plasma concentrations is approximately 1 hour. Administration with food reduces peak concentrations and delays the time to achieve the peak concentrations, but does not affect the extent of drug exposure, as measured by area under the concentration curve (AUC) values.[3–5]

Cetirizine and levocetirizine are highly (91–93%) protein bound. They can cross the blood-brain barrier, but typically occupy only 30–50% of the H1 receptors in the cerebral cortex, compared to more than 90% of peripheral H1 receptors. Approximately 50 to 80% of a cetirizine or levocetirizine dose is excreted in the urine as unchanged drug. Remaining drug undergoes aromatic oxidation and N- and O-dealkylation in the liver to inactive compounds. The average elimination half-life of both drugs is 8 to 9 hours in adults. Cetirizine and levocetirizine are excreted by glomular filtration and active tubular secretion; their clearance correlates with creatinine clearance. Renal impairment reduces their clearance. [3–5]

In a cetirizine pharmacokinetic trial conducted by the manufacturer in children between 7 and 12 years of age, the weight-normalized total body clearance after a 5 mg dose was 33% greater than values observed in adults and the elimination half-life was 33% shorter.[3] Children 2 to 5 years of age who received a 5 mg dose had a total body clearance 81 to 111% greater than that of adults and an elimination half-life that was 33 to 41% shorter.

A similar increase in clearance was observed in a levocetirizine trial conducted in 14 children between 6 and 11 years of age.[4,5] After a 5 mg dose, the average maximum serum concentration and AUC values were approximately 2-fold greater than those in adults. Total body clearance was 30% greater and elimination half-life was 24% shorter than values reported in adults. Although prospective pharmacokinetic trials have not been conducted in younger patients, the manufacturer states that data from a retrospective population pharmacokinetic study in 324 children and adults suggest that children 6 months to 5 years of age given a dose of 1.25 mg once daily achieve plasma levocetirizine concentrations similar to those of adults receiving a 5 mg dose.

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