Loratadine

• Second-Generation H1 Antihistamine
• Peripheral H1 receptor inverse agonist

Parent class: Histamine & Antihistamines

Loratadine selectively blocks peripheral H1 receptors.

• Inhibits histamine-mediated vasodilation
• Decreases capillary permeability
• Reduces pruritus and sneezing
• Minimal blood-brain barrier penetration

Result:

• ↓ rhinorrhea
• ↓ itching
• ↓ sneezing
• Minimal sedation

Unlike first-generation agents, loratadine has minimal central anticholinergic effects.

• Oral administration
• Hepatic metabolism (CYP3A4, CYP2D6)
• Active metabolite: desloratadine
• Duration: ~24 hours
• Once-daily dosing

Avoid strong CYP3A4 inhibitors in high-risk patients.

• Allergic Rhinitis
• Chronic idiopathic urticaria
• Seasonal allergies
• Mild allergic symptoms

Not first-line for nasal congestion (intranasal steroids preferred).

• 10 mg PO once daily

Pediatric dosing varies by age and weight.

Generally well tolerated.

Possible:

• Mild headache
• Dry mouth
• Fatigue (rare)

Minimal sedation compared to first-generation antihistamines.

• Severe hepatic impairment (dose adjustment may be needed)
• Hypersensitivity to drug

• Strong CYP3A4 inhibitors may increase levels
• Rare QT prolongation risk (much lower than older agents)

• Preferred over first-generation antihistamines for daytime use.
• Poor for nasal congestion as monotherapy.
• Does not significantly impair cognition or psychomotor function.
• Once-daily dosing improves adherence.

• Histamine & Antihistamines
• Allergic Rhinitis – Stepwise Therapy
• Urticaria & Angioedema