Megatrol Tablet

Levocetirizine is a selective histamine H₁ antagonist used to treat a variety of allergic symptoms. It is the R enantiomer of cetirizine. Levocetirizine has greater affinity for the histamine H₁ receptor than cetirizine.

Levocetirizine is an H1-receptor antagonist used to treat symptoms associated with chronic allergic rhinitis and uncomplicated cases of chronic idiopathic urticaria.

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.

• Allergic Rhinitis (AR)
• Chronic Idiopathic Urticaria
• Common Cold
• Nasal Congestion
• Perennial Allergic Rhinitis (PAR)
• Seasonal Allergic Rhinitis

Levocetirizine is a second generation histamine H₁ antagonist used to treat various allergic symptoms. 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.

Levocetirizine selectively inhibits histamine H₁ receptors. This action prevents histamine from activating this receptor and causing effects like smooth muscle contraction, increased permeability of vascular endothelium, histidine uptake in basophils, stimulation of cough receptors, and stimulation of flare responses in the nervous system.

Following a 5mg oral dose of levocetirizine, a C_max of 0.27±0.04µg/mL with a T_max of 0.75±0.50h. The AUC of levocetirizine is 2.31±0.50µg*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±0.02L/kg.

Plasma protein binding of levocetirizine was on average 96.1% 1 hour post dose and 91.9% 6 hours post dose.

168 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.

The average clearance of levocetirizine is 0.57±0.18mL/min/kg.

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 240mg/kg.

• Avoid alcohol.
• Take with or without food.

• Mild renal impairment (creatinine clearance: 50-80 ml/min): a dose of 2.5 mg once daily is recommended.
• Moderate renal impairment (creatinine clearance: 30-50 ml/min): a dose of 2.5 mg once every other day is recommended.
• Severe renal impairment (creatinine clearance: 10-30 ml/min): a dose of 2.5 mg twice weekly (administered once every 3-4 days) is recommended.
• End-stage renal disease patients (creatinine clearance: <10 ml/min) and patients undergoing hemodialysis: should not receive Levocetirizine.