TYRIZAL

Levocetirizine is a selective histamine

H 1 antagonist used to treat a variety of allergic symptoms. 2, 3, 4 It is the R enantiomer of cetirizine.

Levocetirizine has greater affinity for the histamine H 1 receptor than cetirizine.

Levocetirizine was granted

FDA approval in 1995.

Levocetirizine is indicated to treat symptoms of perennial allergic rhinitis and uncomplicated skin manifestations of chronic idiopathic urticaria.

It is also used over the counter for a variety of mild allergy symptoms.

Levocetirizine is a second generation histamine

H 1 antagonist used to treat various allergic symptoms. 2, 3, 4 It has a long duration of action as it is generally taken once daily, and a wide therapeutic window as animal studies show the maximal nonlethal dose is over 100x a normal dose.

Patients are cautioned to avoid tasks that require complete alertness, avoid alertness, and use caution in patients with factors predisposing urinary retention.

Following a 5 mg oral dose of levocetirizine, a C max of 0.27±0.04 µg/mL with a T max of 0.75±0.50h.

AUC of levocetirizine is 2.31±0.50 µg*h/mL.

Taking levocetirizine with food does not affect the AUC but delays T max by 1.25 hours and lowers C max by 36%.

The volume of distribution of levocetirizine is 0.33±0.02 L/kg.

Levocetirizine is poorly metabolized with 85.8% of an oral dose being excreted as the unchanged drug.

Levocetirizine can be metabolized to a dihydrodiol (M2), an N-oxide (M3), a hydroxymethoxy derivative (M4), a hydroxy derivative (M5), an O-dealkylated derivative (M6), a taurine conjugate (M8), and an N-dealkylated and aromatic hydroxylated derivative (M9).

M5 metabolite can be glucuronidated to form the M1 metabolite and the M9 metabolite can form 4-chloro-4'-hydroxybenzhydryl mercapturates (M10a and M10b).

Hover over products below to view reaction partners Levocetirizine Levocetirizine Dihydrodiol Metabolite (M2) Levocetirizine Hydroxy Metabolite (M5) + Levocetirizine Hydroxymethoxy Metabolite (M4) Levocetirizine N-oxide Metabolite (M3) Levocetirizine Hydroxy Metabolite (M5) Levocetirizine O-glucuronidated Metabolite (M1) Levocetirizine O-dealkylated Metabolite (M6) Levocetirizine Taurine Conjugated Metabolite (M8) Levocetirizine N-dealkylated and Aromatic Hydroxylated Metabolite (M9) Levocetirizine 4-chloro-4'-hydroxybenzhydryl Mercapturate Metabolites (M10a and M10b).

hours post dose an average of 85.4% of a radiolabeled dose was recovered with an average of 80.8% in the urine and 9.5% in the feces.

In the urine, 77% of the dose was recovered as unchanged drug, 0.5% as the M8 and M9 metabolites, 0.4% as the M10a metabolite, 0.4% as the M10b metabolite, 0.3% as the M3 metabolite, 0.3% as the M4 and M5 metabolite, 0.2% as the M2 metabolite, and 0.1% as the M1 metabolite.

In the feces, 9.0% of the dose was recovered as unchanged drug, 1.0% as the M4 and M5 metabolite, and 0.1% as the M1 metabolite.

The average half life of levocetirizine is 7.05±1.54 hours.

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Patients experiencing an overdose may present with drowsiness.

Children may become agitated and restless before drowsiness.

Patients should be treated with supportive measures.

Dialysis will not assist in removing the drug from the body.

The maximal nonlethal dose in mice and rats is 240 mg/kg.