Sign Out
ATC Code: R06A E09.
Pharmacology: Pharmacodynamics: Levocetirizine is the active component of cetirizine. It is a selective competitive inhibitor for the H1-histamine receptor, both in vitro and in vivo.
Pharmacokinetics: Absorption: Levocetirizine is rapidly and extensively absorbed following oral administration. Steady state is achieved after 2 days. Peak concentrations are typically 270 and 308 ng/mL following a single and repeated 5mg once daily dose, respectively. The extent of absorption is dose-independent and is not altered by food. However, the peak concentration is reduced and delayed. Therefore, levocetirizine can be administered with or without food.
Distribution: No tissue distribution data are available in humans. Levocetirizine is 90% bound to plasma proteins. The distribution of levocetirizine as the volume of distribution is 0.4 L/kg.
Metabolism: The extent of metabolism of levocetirizine in humans is less than 14% of the dose and therefore differences resulting from genetic polymorphism or concomitant intake of hepatic drug metabolizing enzyme inhibitors are expected to be negligible. Metabolic pathways include aromatic oxidation, N- and O-dealkylation, and taurine conjugation. Dealkylation pathways are primarily mediated by CYP 3A4 while aromatic oxidation involves multiple and/or unidentified CYP isoforms.
Elimination: The plasma half-life in adult healthy subjects is 7.9 +/- 1.9 hours. The mean oral total body clearance for levocetirizine is 0.63 mL/kg/min. The major route of excretion of levocetirizine and its metabolites is via urine.
Excretion via faeces accounts for only 12.9% of the dose. Levocetirizine is excreted both by glomerular filtration and active tubular secretion. In patients with renal impairment the clearance of levocetirizine is reduced.
