Cetirizine

Class: Second-generation antihistamine (H1-receptor antagonist)

Indications: Allergic rhinitis, chronic urticaria, seasonal allergies, atopic conditions

Mechanism: Selectively blocks peripheral H1-receptors, reducing histamine-mediated symptoms. Less sedating than first-generation antihistamines.

Dosage

• Adults & ≥12 yrs: 10 mg once daily (5 mg may be sufficient for mild symptoms)
• Children 6–11 yrs: 5–10 mg once daily
• Children 2–5 yrs: 2.5 mg twice daily or 5 mg once daily
• Children 6 mo–2 yrs: 2.5 mg once daily (can increase to twice daily if needed)
• Max dose: 10 mg/day

Major Side Effects

• Drowsiness (less common than first-generation antihistamines)
• Fatigue
• Dry mouth
• Headache
• Occasionally gastrointestinal upset

Contraindications

• Hypersensitivity to cetirizine, hydroxyzine, or any component
• Severe renal impairment (dose adjustment required)

Compatible Solvent / Administration

• Oral tablets, syrup, chewable tablets
• Take with or without food, with water

Special Precautions

• Caution in patients with renal or hepatic impairment
• May cause mild sedation in sensitive individuals — avoid driving if drowsy
• Pregnancy Category B – relatively safe
• Safe for children ≥6 months under medical guidance