levocetirizine

Levocetirizine is a selective peripheral antihistamine used to treat symptoms of allergic rhinitis and chronic idiopathic urticaria. It is the active enantiomer of cetirizine and is marketed as a stand-alone medication in many countries.

Pharmacology and mechanism of action

Levocetirizine acts as an antagonist of the H1 histamine receptor. By blocking histamine effects in the nasal passages and skin, it helps reduce sneezing, itching, rhinorrhea, nasal congestion, and dermatologic symptoms associated with allergic reactions. It is classified as a second-generation antihistamine, intended to have fewer central nervous system effects than first-generation agents.

Pharmacokinetics

Levocetirizine is administered orally and is rapidly absorbed, with peak plasma concentrations reached within about one hour. It has a relatively long duration of action, with a typical half-life of roughly 7 to 10 hours in adults. Most of the drug is excreted unchanged in the urine, with limited hepatic metabolism, leading to relatively few drug interactions related to liver enzymes.

Indications and administration

Approved uses include relief of symptoms of seasonal and perennial allergic rhinitis and treatment of chronic idiopathic urticaria. Dosing is commonly 5 mg once daily for adults, with lower doses (often 2.5 mg daily) used for certain pediatric populations or in those with reduced kidney function. Dosing should be tailored to age, kidney function, and symptom severity.

Safety and precautions

Levocetirizine is generally well tolerated. Common adverse effects include drowsiness, fatigue, dry mouth, and headache. Caution is advised for patients with renal impairment, elderly individuals, and those who operate machinery or drive, especially at higher doses. It should be avoided in individuals with known hypersensitivity to the drug. Pregnancy and lactation considerations require medical advice, as data are limited.

Regulatory status

In many regions, levocetirizine is available over the counter or by prescription, depending on local regulations. It is related to cetirizine but is used specifically as the active enantiomer.