A-Leaze Mechanism of Action

Pharmacology: Pharmacodynamics: Levocetirizine is the R-enantiomer of cetirizine. Levocetirizine is a third generation antihistamine and is selective for peripheral H₁-receptors. Levocetirizine is less sedating.
Levocetirizine (at half dose the dosage of cetirizine) appears to be as potent as cetirizine in inhibiting histamine-inducing sneezing, increased nasal airway resistance, and skin wheal and flare.
Pharmacokinetics: Absorption: Levocetirizine is rapidly and extensively absorbed following oral administration with peak plasma concentration usually attained in 0.9 hour. Antihistaminic effects occur within 1 hour. Antihistaminic effects persist for at least 24 hours. A high-fat meal reduces peak plasma concentration by about 36% and delays time to peak plasma concentration by 1.25 hours, but has no effect on AUC.
Distribution: Volume of distribution is 0.4 L/kg. Levocetirizine is approximately 91-92% bound to plasma protein.
Metabolism: Hepatic metabolism is limited extent, less than 14% by aromatic oxidation, N-dealkylation, O-dealkylation, and taurine conjugation.
Excretion: Levocetirizine and metabolites is excreted via urine (85.4%) (via glomerular filtration and active tubular secretion) and in feces (12.9%). Half-life is approximately 8-9 hours in adults.