What is Cetirizine Hydrochloride?

 

Cetirizine Hydrochloride

Chemical Structure and Properties

Cetirizine hydrochloride is a piperazine derivative that acts as a potent and selective H1 receptor antagonist. Its chemical name is (±)--1-piperazinyl] ethoxy]acetic acid dihydrochloride. The structural formula is C21H25ClN2O3•2HCl.

Cetirizine hydrochloride is a white, crystalline powder that is freely soluble in water and insoluble in most organic solvents. Its molecular formula is C21H25ClN2O3•2HCl and molecular weight is 461.82 g/mol. It has a melting point range of 225-228°C and pKa of approximately 4.0. Chemically, it is considered a hydrophilic tertiary amine salt.

Mechanism of Action

Cetirizine Hydrochloride acts as a potent and selective antagonist of peripheral H1 receptors. These receptors are found both centrally and peripherally in the body, with higher concentrations in the brain, spinal cord, lungs and gastrointestinal tract. H1 receptors play a key role in type I hypersensitivity reactions, such as those involved in allergic rhinitis and chronic idiopathic urticaria.

When an allergen binds to IgE antibodies fixed on mast cells and basophils, it causes the cells to degranulate and release histamine and other inflammatory mediators. Histamine then binds to H1 receptors located on effector cells to produce signs and symptoms of allergy. Cetirizine selectively blocks these H1 receptors, thereby inhibiting the physiologic effects of histamine. This antihistaminic action accounts for its therapeutic effects in conditions involving histamine release and H1 receptor stimulation.

Pharmacokinetics

Cetirizine hydrochloride is rapidly and well absorbed after oral administration, with peak plasma concentrations occurring 1-2 hours after ingestion. It undergoes extensive first-pass hepatic metabolism via cytochrome P450 isoenzymes to form the 5-hydroxylated active metabolite, which accounts for most of its clinical efficacy.

The half-life of cetirizine is approximately 10 hours in adults and allows for once-daily dosing. Steady-state levels are achieved within 3-4 days. Only a small fraction of the drug is excreted unchanged in the urine. Protein binding of cetirizine is approximately 83% and is independent of drug concentration.

Clinical Uses

Allergic Rhinitis

As a second-generation H1 receptor antagonist, cetirizine is widely used for the treatment of seasonal and perennial allergic rhinitis. It relieves symptoms such as sneezing, runny nose, nasal congestion and itching of the eyes, nose and throat that are triggered by various environmental allergens. Numerous clinical studies have demonstrated cetirizine's efficacy and tolerability in managing allergic rhinitis when administered orally.

Chronic Idiopathic Urticaria

Cetirizine has shown to be effective in the treatment of chronic idiopathic urticaria, as it has antihistaminic properties that antagonize the action of histamine at H1 receptors. This helps reduce hives and itching that often accompany chronic urticaria. Clinical trials have established cetirizine's safety and effectiveness in relieving symptoms of chronic urticaria when taken daily.

Other Indications

Due to its peripheral H1 receptor selectivity and anti-allergic properties, cetirizine may also be used in conditions like chronic spontaneous urticaria, insect venom hypersensitivity, and food allergies where mast cell degranulation is involved. It has the potential to inhibit cutaneous manifestations of systemic mastocytosis and menopausal flushing.

Dosage and Administration of Cetirizine Hydrochloride

The standard oral dosage of cetirizine is 10-20 mg/day, which can be administered as a single daily dose with or without food.

For the treatment of seasonal and perennial allergic rhinitis, the recommended dose is 10 mg once daily or 5 mg twice daily. In chronic idiopathic urticaria, cetirizine is usually given at 10-20 mg daily.

Pediatric doses for children 6 months to 12 years depend on age, with maximum doses ranging from 5-10 mg/day. Cetirizine is also available as chewable tablets or oral solutions for children who have difficulty swallowing whole tablets.

Adverse Effects

Cetirizine is generally well tolerated with a good safety profile at therapeutic doses. Common side effects reported include somnolence, fatigue, headache, dry mouth and exacerbation of asthma. However, these adverse reactions are usually mild to moderate in severity and tend to decrease over time.

Rarely, gastrointestinal disturbances, dizziness and rashes have been seen. Very infrequent cases of priapism have been linked to cetirizine, similar to other antihistamines. No serious toxicity or drug interactions have been reported when cetirizine is used appropriately.

Precautions and Contraindications

People with impaired liver function need to exercise caution with cetirizine due to decreased metabolism and clearance. Dosage adjustments may be necessary in severe hepatic impairment.

Cetirizine hydrochloride should also be used cautiously in those with pre-existing conditions like renal insufficiency, asthma, cardiovascular disease, seizure disorders, urinary retention and narrow-angle glaucoma.

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Ravina Pandya, Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. (https://www.linkedin.com/in/ravina-pandya-1a3984191)