Levocetirizine is a second-generation antihistamine used to treat allergic conditions such as seasonal allergic rhinitis, perennial allergies, and chronic urticaria. It works by blocking histamine (H1) receptors in the body, thereby relieving symptoms like sneezing, runny or blocked nose, itchy or watery eyes, and skin itching. It is the active enantiomer of cetirizine, making it more selective and generally associated with fewer sedative effects, although mild drowsiness, fatigue, dry mouth, or headache can still occur in some individuals. It is usually taken once daily, often in the evening, and is effective for both short-term and long-term allergy relief. Levocetirizine was introduced in the early 2000s and approved for medical use around 2001, and it is now widely available as a generic medication. Caution is advised in people with kidney problems, and it should be used under medical guidance during pregnancy or breastfeeding.
BRAND NAMES
Xyzal: The primary branded version (often available OTC or prescription).
Teczine: Manufactured by Sun Pharmaceutical Industries Ltd.
Levorid: Manufactured by Cipla.
Vozet: Manufactured by Dr. Reddy's Laboratories.
Lecope: Manufactured by Mankind Pharma.
Lezyncet: Manufactured by Torrent Pharmaceuticals.
MECHANISM OF ACTION
Levocetirizine works by selectively blocking histamine H1 receptors in the body. During an allergic reaction, the body releases histamine, which binds to these H1 receptors and causes symptoms such as sneezing, itching, swelling, increased mucus production, and redness. Levocetirizine acts as an H1 receptor antagonist, preventing histamine from attaching to these receptors and thereby reducing or stopping the allergic response.
PHARMACOKINETICS
Absorption
Levocetirizine is rapidly and well absorbed after oral administration, with peak plasma concentrations typically reached within about 0.9 to 1 hour. Its oral bioavailability is high, meaning most of the drug enters the bloodstream effectively.
Distribution
Levocetirizine is widely distributed in the body after absorption, with a relatively low volume of distribution, indicating that it mainly stays within the blood and extracellular fluids rather than extensively entering tissues. It has about 90% plasma protein binding, which helps maintain stable drug levels in the bloodstream
Metabolism
Levocetirizine undergoes minimal metabolism in the body. Most of the drug is not significantly broken down by liver enzymes and remains largely unchanged after administration. Only a small fraction is metabolized, and it does not strongly involve the cytochrome P450 enzyme system, which reduces the risk of drug–drug interactions.
Excretion
Levocetirizine is mainly excreted unchanged through the kidneys in urine. About 85–90% of the dose is eliminated in this way, while only a small amount is removed through feces. Its elimination depends largely on kidney function, so patients with reduced renal function may require dose adjustment. The elimination half-life is around 7–10 hours in healthy adults, allowing for once-daily dosing.
PHARMACODYNAMICS
Levocetirizine is a selective, second-generation H1 receptor antagonist that produces its therapeutic effects by competitively and reversibly blocking peripheral histamine H1 receptors. By preventing histamine from binding to these receptors, it reduces the release of inflammatory mediators responsible for allergic symptoms such as itching, sneezing, rhinorrhea, and urticaria. It has a high affinity for H1 receptors and minimal activity on other receptor systems, which contributes to its good safety profile and low anticholinergic effects.
ADMINISTRATION
Levocetirizine is administered orally, usually in the form of tablets, oral solution, or syrup. It is typically taken once daily, with or without food, preferably in the evening if drowsiness occurs. The tablet should be swallowed with water, and the dose is adjusted based on age, symptoms, and kidney function.
DOSAGE AND STRENGTH
Levocetirizine is commonly available in the following strengths and dosages:
Strengths
2.5 mg (mostly for children or syrup form)
5 mg (most common adult tablet strength)
Usual dosage
Adults & children ≥12 years: 5 mg once daily
Children 6–11 years: 2.5 mg once daily (or as prescribed)
Children 6 months–5 years: lower doses (usually syrup form, doctor-guided)
DRUG INTERACTIONS
Levocetirizine has few drug interactions, but it can increase drowsiness when taken with alcohol, sedatives, sleeping pills, or opioid painkillers. It should be used cautiously with other antihistamines, as this may increase side effects without added benefit.
FOOD INTERACTIONS
Levocetirizine has minimal food interactions. It can be taken with or without food, and most foods do not significantly affect its absorption or effectiveness. However, taking it with a heavy meal may slightly delay its onset of action, but this is not usually clinically important. Alcohol should be avoided as it can increase drowsiness.
CONTRAINDICATIONS
Levocetirizine is contraindicated in patients with a known hypersensitivity (allergy) to levocetirizine, cetirizine, hydroxyzine, or any component of the formulation. It should also be avoided in patients with severe renal impairment or end-stage kidney disease without appropriate dose adjustment, as the drug is primarily excreted unchanged through the kidneys.
SIDE EFFECTS
Drowsiness / fatigue (somnolence) – most common side effect
Dry mouth (xerostomia)
Headache
Dizziness
Nausea, vomiting, diarrhea, constipation (gastrointestinal effects)
Cold-like symptoms such as sore throat (nasopharyngitis)
Nasal dryness or coughing
OVER DOSE
Excessive drowsiness / severe sleepiness
Extreme fatigue or weakness
Dizziness
Dry mouth
Restlessness or agitation (especially in children)
TOXICITY
Levocetirizine toxicity is usually low, but in overdose it may cause excessive drowsiness, dizziness, confusion, or agitation (especially in children). Severe cases can lead to rapid heartbeat and strong sedation. Treatment is supportive.
