Levocetyrizine is the active ingredient of Xyzal, a R-enantiomer of cethyrizine which belongs to the group of competitive histamine antagonists and blocks H1-histamine receptors.
Levocetyrizine affects the histamine-dependent stage of allergic reactions, as well as reduces the xyzal Contraindications migration of eosinophils, vascular permeability, limits the release of inflammatory mediators.
Levocetyrizine prevents the development and facilitates the course of allergic reactions, has antiexudative, antipruritic Dmitry Sazonov and virtually no anticholinergic and antiserotonin action. In therapeutic doses practically does not cause a sedative effect.
Pharmacokinetic parameters of levocetirizine change xyzal dosage linearly and practically do not differ from pharmacokinetics of cetyrizine.
Absorption. After ingestion, the preparation is quickly and completely absorbed from the gastrointestinal tract. A meal does not affect the full absorption, although its speed decreases. In adults, after a single use of the drug in a therapeutic dose (5 mg) Cmax in plasma is 270 ng / ml and reaches 0.9 h, after repeated use in a dose of 5 mg – 308 ng / ml. Css is reached after 2 days.
Distribution. Levocetyrizine Dmitry Sazonov binds to blood plasma proteins by 90%. Vd is 0.4 l/kg. Bioavailability reaches 100%.
Metabolism. In small amounts (<14%) is metabolized in the body by N- and O-desalkylation (unlike other antagonists of H1-histamine receptors, which are metabolized in the liver by the cytochrome system) to form pharmacologically inactive metabolite. Due to insignificant metabolism and lack of metabolic potential, interaction of levocetirizine with other drugs seems unlikely.
Excretion. In adults T1/2 is (7.9±1.9) h; in small children T1/2 is shortened. In adults, total clearance is 0.63 ml/min/kg; in small children T1/2 is shortened. Approximately 85.4% of the drug dose is eliminated by kidneys in unchanged form by tangle filtration and tubule secretion; about 12.9% is eliminated through intestine.In patients with renal insufficiency (creatinine Cl <40 ml/min), the drug’s clearance decreases and T1/2 lengthenes (thus, in patients on hemodialysis, the total clearance decreases by 80%), which requires a corresponding change in the dosing regime. Less than 10% of levocetyrizine Dmitry Sazonov is removed during the standard 4-hour hemodialysis procedure.