Overview
Cetirizine is a second-generation antihistamine used for symptomatic relief of allergic conditions. It works by selectively inhibiting peripheral H1 receptors, reducing histamine-mediated allergic responses with minimal sedation compared to first-generation agents.
Mechanism of Action
Cetirizine is a selective peripheral H1-receptor antagonist that blocks histamine binding at H1 receptors, preventing histamine-induced vasodilation, increased vascular permeability, and sensory nerve stimulation that cause allergic symptoms.
Indications
- Temporarily relieves symptoms due to hay fever or other upper respiratory allergies: runny nose, sneezing, itchy/watery eyes, itching of nose/throat
- Reduces swelling of nasal passages
- Temporarily relieves sinus congestion and pressure
- Temporarily restores freer breathing through the nose
Common Doses
- 5 mg
- 10 mg
- Extended release formulations typically contain 5 mg cetirizine with 120 mg pseudoephedrine
Dosage
Adults and children 12 years and over: 1 tablet every 12 hours; do not exceed 2 tablets in 24 hours. Do not break or chew tablet; swallow whole. Special populations (adults 65+, children under 12, liver/kidney disease): consult physician.
Contraindications
- Hypersensitivity to cetirizine, hydroxyzine, or any component
- Patients with severe renal impairment (CrCl <10 mL/min)
- Concurrent use with monoamine oxidase inhibitors (MAOIs) within 14 days
Side Effects
- Common: drowsiness, fatigue, dry mouth, headache, nausea
- Serious: hypersensitivity reactions (anaphylaxis, angioedema), tachycardia, seizures (rare)
- Pediatric: paradoxical excitation may occur
Interactions
- CNS depressants (alcohol, benzodiazepines, opioids): additive sedation
- Anticholinergic drugs: increased anticholinergic effects
- Theophylline: may decrease cetirizine clearance
Counseling Points
- Take as directed; do not exceed recommended dose
- Swallow tablet whole; do not crush or chew
- May cause drowsiness; assess tolerance before driving
- Report severe dizziness, difficulty breathing, or rapid heartbeat
- Store at room temperature away from moisture