Cetirizine
Generic Name: Cetirizine Hydrochloride
Uses & Medical Indications
Relief of symptoms associated with seasonal and perennial allergic rhinitis (sneezing, rhinorrhea, nasal itching, itchy watery eyes) and uncomplicated skin manifestations of chronic idiopathic urticaria (hives).
Allergic Rhinitis, Urticaria (Hives), Allergic Conjunctivitis, Pruritus
Work Mechanism & Pharmacology
Patient Overview of Work Mechanism
Cetirizine blocks histamine, the natural allergic substance released during pollen or dust exposure, relieving sneezing, runny nose, itchy eyes, and hives without causing heavy drowsiness.
Clinical Mechanism of Action (MoA)
Potent, selective second-generation peripheral histamine H1 receptor inverse agonist. Displaces histamine from peripheral H1 receptors on vascular endothelial cells, bronchial smooth muscle, and cutaneous sensory nerve endings, inhibiting histamine-mediated allergic flare, wheal, pruritus, and vascular permeability.
Dosage & Administration Guidelines
5 mg to 10 mg orally once daily depending on symptom severity.
Children 6 months to 2 years: 2.5 mg once daily (up to 2.5 mg twice daily for >12 months). Children 2-5 years: 2.5 mg to 5 mg daily. Children ≥6 years: 5 to 10 mg daily.
Start with 5 mg once daily due to decreased renal clearance.
10 mg once daily.
eGFR 11-31 mL/min: 5 mg every other day. Hemodialysis: 5 mg every other day.
5 mg once daily in hepatic impairment.
Side Effects & Safety Warnings
Mild somnolence / drowsiness (in ~10%), fatigue, dry mouth, headache, pharyngitis.
Severe sedation, urinary retention (in BPH), paradoxical excitation in young children (rare).
Severe renal impairment (eGFR <10 mL/min), hypersensitivity to cetirizine or hydroxyzine.
May cause drowsiness; use caution when driving or operating heavy machinery.
Interactions (Drugs, Food & Alcohol)
CNS depressants, Alcohol, Sedatives (additive drowsiness).
Can be taken with or without food.
Avoid alcohol; alcohol significantly intensifies drowsy sedation.
Pregnancy & Breastfeeding Safety
Considered one of the preferred second-generation antihistamines of choice during pregnancy.
Compatible in low doses; small amounts enter breast milk.
Patient Counseling & Practical Advice
Best taken in the evening if it causes slight drowsiness. Fast-acting; provides 24-hour relief.
Take when remembered. Do not take more than 10 mg in 24 hours.
Relief of allergy symptoms.
Frequently Asked Questions
When to Seek Urgent Medical Attention
Difficulty breathing, facial swelling (anaphylaxis requires epinephrine, not just oral antihistamines).
Content for Cetirizine was synthesized from standardized public health monographs, official pharmacopoeias, and health authorities:
- American Academy of Allergy, Asthma & Immunology (AAAAI) — Rhinitis Practice Parameters
The information provided on this website is for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition.