Cetirizine

• Second-Generation H1 Antihistamine
• Peripheral H1 receptor inverse agonist
• Active metabolite of hydroxyzine

Parent class: Histamine & Antihistamines

Cetirizine selectively blocks peripheral H1 receptors.

Effects:

• ↓ Histamine-mediated vasodilation
• ↓ Capillary permeability
• ↓ Pruritus
• ↓ Sneezing and rhinorrhea

Compared to first-generation antihistamines:

• Minimal anticholinergic activity
• Limited blood-brain barrier penetration
• Low but not zero sedation

• Oral administration
• Rapid onset (~1 hour)
• Duration: ~24 hours
• Primarily renally eliminated
• Minimal hepatic metabolism

Dose adjustment required in renal impairment.

• Allergic Rhinitis
• Chronic idiopathic urticaria
• Seasonal allergies
• Pruritus

Effective for:

• Sneezing
• Itching
• Rhinorrhea

Less effective for:

• Nasal congestion (intranasal steroids superior)

• 10 mg PO once daily
• Consider 5 mg daily in renal impairment

Pediatric dosing based on age.

Generally well tolerated.

Possible:

• Mild drowsiness (more than loratadine)
• Fatigue
• Dry mouth (rare)

Sedation risk:

• Higher than loratadine
• Lower than diphenhydramine

• Severe renal impairment (dose adjust)
• Hypersensitivity

Use caution:

• Elderly
• Concomitant CNS depressants

• Minimal CYP interaction
• Additive sedation with alcohol or CNS depressants

• Slightly more effective for urticaria than loratadine.
• Slightly more sedating than loratadine.
• Good balance of potency and tolerability.
• Renal clearance makes it safer in hepatic disease.

• Histamine & Antihistamines
• Hydroxyzine
• Levocetirizine
• Allergic Rhinitis – Stepwise Therapy