Cetirizine

Cetirizine is a selective histamine antagonist and is used in allergic rhinitis and chronic urticaria. It belongs to the second-generation antihistamines.

Indications and use

Cetirizine is an orally active second-generation histamine _H1 antagonist effective in the treatment of various allergic symptoms such as sneezing, cough, nasal congestion, and hives. One of the most common uses of this medication is in the treatment of hay fever (allergic rhinitis). However, cetirizine can also be used for symptomatic treatment of other allergic reactions.

Cetirizine is usually administered in the form of film-coated tablets. However, there are also formulations i.e. drops or oral solutions. Dosages are usually 10 mg film-coated tablets and 10 mg/ml or 1 mg/ml as drops and solution.

History

It was patented by USB Pharmaceuticals in 1981 and was first approved in 1987. It is on the World Health Organization's list of essential medicines and is available as a generic.

Pharmacodynamics and mechanism of action

The main action of cetirizine is achieved through its highly selective inhibition of peripheral_{H1 receptors}. By binding and inhibiting these receptors, it minimizes or eliminates symptoms caused by histamine release, such as sneezing, itching, watery eyes, and runny nose. Cetirizine is not or minimally CNS-responsive, so it is not expected to cause central side effects such as sedation or drowsiness.

Cetirizine also exhibits anti-inflammatory properties independent of_{H1 receptors}. The effect is achieved by probably suppressing the NF-κB pathway and regulating the release of cytokines and chemokines, thereby regulating the recruitment of inflammatory cells. This mechanism is currently the subject of various investigations, but it is not yet relevant for therapeutic application.

Pharmacokinetics

Cetirizine is rapidly absorbed after oral administration. The time to maximum concentration (Tmax) is approximately 1 hour. Food intake has no effect on blood cetirizine concentrations, but Tmax is delayed by approximately 1 hour. The mean plasma protein binding of cetirizine is 93%. Approximately 50% of the dose is excreted in the urine as unchanged cetirizine. Cetirizine is metabolized primarily by oxidative O-dealkylation. The enzyme or enzymes responsible for this step of cetirizine metabolism have not yet been identified. Between 70-85% of the orally administered dose is excreted in the urine and 10-13% in the feces. The plasma elimination half-life is approximately 8 hours.

Drug Interactions

Since cetirizine, unlike many other drugs, is not degraded via the CYP450 enzyme system, the risk for serious interactions is relatively low.

Contraindications

Cetirizine must not be taken if:

• there is a known allergy to the active substance
• severe renal dysfunction exists (creatinine clearance < 10 ml/min)

Side effects

Common side effects of cetirizine include:

• dizziness
• drowsiness
• drowsiness
• dry mouth
• sore throat
• cough
• nausea
• diarrhea
• constipation
• Headache
• Restlessness
• Paresthesias

Pregnancy and lactation

Cetirizine use is not thought to harm the fetus, but because of limited data on safety during pregnancy, it should be avoided or used only as directed by a physician.

Cetirizine may pass into breast milk and cause appropriate side effects in the infant. Therefore, its use during breastfeeding is strictly discouraged.