2-(2-{4-[(R)-(4-chlorophenyl)(phenyl)methyl]piperazin-1-yl}ethoxy)acetic acid

1. 成人及十二歲以上青少年：建議每日劑量為5mg。
2. 老年患者：具有中度到嚴重腎功能障礙的老年患者，需調整其劑量。
3. 六歲至十二歲孩童：建議每日劑量為5mg。
4. 六歲以下孩童尚不建議使用。

Absorption

Rapidly and extensively absorbed. T _max is 0.9 h. C _max is 270 and 308 ng/mL after single and repeated once-daily dosing, respectively. Steady state achieved after 2 days. Food delayed T _max by approximately 1.25 h and decreased C _max by approximately 36%.

Distribution

Plasma protein binding is approximately 92%. Vd is approximately 0.4 L/kg.

Metabolism

Metabolism is less than 14% and by aromatic oxidation, N- and O-dealkylation, and taurine conjugation.

Elimination

The half-life is about 8 to 9 h. Elimination is 85.4% and 12.9% via urine and feces, respectively. Excreted both by glomerular filtration and active tubular secretion.

No formal in vivo drug-drug interaction studies have been performed with levocetirizine. Drug interaction studies have been performed with racemic cetirizine.

Alcohol, CNS depressants

Additive CNS depressant effects; concurrent use should be avoided.

Food

Food had no effect on the extent of levocetirizine exposure; however, the half-life was delayed about 1.25 hours and the C _max was decreased about 36% after administration with a high-fat meal. Levocetirizine may be taken without regard to food.

Ritonavir

Cetirizine AUC and half-life may be increased, while Cl may be decreased. The risk of adverse reactions may be increased.

Theophylline

May decrease cetirizine Cl.