What it does
Cetirizine is an antihistamine that helps relieve allergy symptoms.
Commonly used for: hay fever (allergic rhinitis), allergic skin reactions (urticaria), itching
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Source: Pharmacy and Poisons Board · fetched 2026-01-28 19:56:16 · updated 2026-08-03 03:05:34
About this medicine
Cetirizine is an antihistamine that helps relieve allergy symptoms.
What it treats
- hay fever (allergic rhinitis)
- allergic skin reactions (urticaria)
- itching
How it works
Cetirizine works by blocking the action of histamine, a substance in the body that causes allergic symptoms.
Who it's for
It is suitable for adults and children aged 6 years and older who suffer from allergies.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: ceterizine
Cetirizine is an antihistamine used primarily for the relief of allergic symptoms such as rhinitis and urticaria. It is a selective antagonist of peripheral H1 receptors, which helps reduce the effects of histamine in the body, leading to alleviation of allergy symptoms. Cetirizine is commonly used for the treatment of hay fever, seasonal allergies, and chronic urticaria.
Indications
- Allergic rhinitis
- Seasonal allergic rhinitis
- Perennial allergic rhinitis
- Chronic urticaria
Dosage
Children: Refer to the BNF for Children for specific dosing recommendations.
Adults: Refer to the BNF for specific dosing recommendations.
Mechanism of action
Cetirizine works by selectively blocking the H1 histamine receptors, preventing histamine from exerting its effects. This action reduces vasodilation, increased vascular permeability, and sensory nerve stimulation caused by histamine release during allergic reactions.
Pharmacodynamics
The pharmacodynamic effects of cetirizine include decreased allergic symptoms such as sneezing, itching, and nasal congestion. Cetirizine has a rapid onset of action, typically within one hour of administration, and its effects can last for 24 hours, making it suitable for once-daily dosing. Unlike some first-generation antihistamines, cetirizine is less likely to cause sedation due to its reduced ability to cross the blood-brain barrier.
Pharmacokinetics
Cetirizine is well absorbed after oral administration, with peak plasma concentrations occurring within one hour. It has a bioavailability of approximately 93%. The drug is extensively metabolized in the liver, primarily via conjugation, and is excreted in the urine, with about 70% of an administered dose excreted unchanged. The elimination half-life of cetirizine is approximately 8 hours in healthy adults, which can be prolonged in individuals with renal impairment.
Contra-indications
- Hypersensitivity to cetirizine or any of its components
- Severe renal impairment
Adverse effects
- Drowsiness
- Dry mouth
- Fatigue
- Headache
- Nausea
- Dizziness
- Gastrointestinal disturbances
Interactions
- CNS depressants may enhance sedative effects
- Alcohol may increase drowsiness
Precautions
- Caution in patients with epilepsy or at risk of seizures
- Caution in patients with hepatic impairment
- Not recommended for use in children under 2 years of age
Pregnancy
Cetirizine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Limited data are available.
Breast-feeding
Cetirizine is excreted in breast milk, and caution should be exercised when administering to nursing women.
Storage
Store at room temperature, away from moisture and direct sunlight. Keep out of reach of children.
Formulations
- Tablets
- Oral solution
- Chewable tablets
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.