Cetirizine: Antihistamine for Allergy Relief
Cetirizine is a second-generation antihistamine used to treat allergies, hay fever, and hives. It selectively blocks histamine receptors and causes little to no drowsiness.
Things worth knowing about "Cetirizine"
Cetirizine is a second-generation antihistamine used to treat allergies, hay fever, and hives. It selectively blocks histamine receptors and causes little to no drowsiness.
What is Cetirizine?
Cetirizine is a second-generation antihistamine widely used to relieve symptoms of allergic conditions. It works by selectively blocking H1 histamine receptors, thereby reducing typical allergy symptoms such as sneezing, itching, runny nose, and watery eyes. Compared to first-generation antihistamines, cetirizine causes significantly less sedation because it crosses the blood-brain barrier only to a minimal extent.
Indications
Cetirizine is indicated for the following conditions:
- Allergic rhinitis (seasonal hay fever and perennial allergic rhinitis)
- Chronic idiopathic urticaria (hives of unknown origin)
- Allergic conjunctivitis (allergic eye inflammation)
- Skin allergies with itching
- Reactions to insect bites and stings
Mechanism of Action
Cetirizine is a selective peripheral H1 receptor antagonist. Histamine is a naturally occurring chemical messenger released from mast cells during allergic reactions. When histamine binds to H1 receptors, it triggers symptoms such as itching, vasodilation, mucosal swelling, and increased mucus production. Cetirizine competitively occupies these receptors without activating them, thereby blocking the effects of histamine. In addition, cetirizine inhibits the migration of eosinophilic granulocytes, which accounts for its anti-inflammatory properties.
Dosage
The standard dose for adults and children aged 12 and over is 10 mg of cetirizine once daily, preferably in the evening. For children between 6 and 12 years of age, 5 mg twice daily is generally recommended. Dose adjustment is necessary in patients with renal impairment, as cetirizine is primarily excreted via the kidneys. It can be taken with or without food.
Side Effects
Cetirizine is generally well tolerated. Possible side effects include:
- Common: Drowsiness (though less than first-generation antihistamines), dry mouth, headache, dizziness
- Occasional: Gastrointestinal discomfort, nausea, fatigue
- Rare: Hypersensitivity reactions, cardiac arrhythmias (at very high doses), elevated liver enzymes
Cetirizine should only be taken during pregnancy or breastfeeding after consultation with a healthcare professional.
Interactions
Cetirizine may enhance the sedative effects of alcohol, sleeping aids, and other central nervous system depressants. Concomitant use of theophylline may slightly reduce the clearance of cetirizine. Overall, the interaction potential of cetirizine is considered low.
Contraindications
Cetirizine should not be used in patients with:
- Known hypersensitivity to cetirizine or hydroxyzine
- Severe renal insufficiency (without medical supervision)
- Children under 2 years of age (in most formulations)
References
- European Medicines Agency (EMA): Summary of Product Characteristics for Cetirizine. www.ema.europa.eu
- Simons F.E.R. - Advances in H1-Antihistamines. New England Journal of Medicine, 2004; 351(21):2203-2217.
- Zuberbier T. et al. - The EAACI/GA2LEN/EDF/WAO Guideline for the Definition, Classification, Diagnosis and Management of Urticaria. Allergy, 2018; 73(7):1393-1414.
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