Loratadine is a second-generation antihistamine that selectively antagonizes peripheral H₁ histamine receptors, inhibiting histamine-mediated allergic responses. Key features include:

1. Peripheral Selectivity: Minimal penetration of the blood-brain barrier, reducing sedative effects compared to first-generation antihistamines (Lippincott).
2. Anti-inflammatory Effects: Blocks histamine-induced vasodilation, bronchoconstriction, and pruritus.
3. Long Duration: Provides 24-hour relief with once-daily dosing due to prolonged receptor binding (Lange).

Loratadine is approved for:

1. Allergic Rhinitis:
   • Seasonal (hay fever) and perennial allergic rhinitis in adults and children ≥2 years (BNF).
2. Chronic Idiopathic Urticaria:
   • Reduces itching and hives in patients ≥2 years.
3. Off-Label Uses:
   • Mild allergic conjunctivitis (adjunct therapy).

Adults and Adolescents (≥12 years):

• Oral: 10 mg once daily.

Children:

• 2–12 years (≥30 kg): 10 mg once daily.
• 2–12 years (<30 kg): 5 mg once daily (syrup or tablet).

Special Populations:

• Hepatic Impairment: Reduce dose to 10 mg every other day (BNF).
• Renal Impairment: No dose adjustment required.
• Elderly: Standard dosing applies unless hepatic impairment is present.

Administration Tips:

• Take with or without food.
• Avoid grapefruit juice (may inhibit CYP3A4, increasing plasma levels).

• Common (≥1%): Headache, dry mouth, fatigue, somnolence.
• Rare (<1%):
  • Dizziness, gastrointestinal disturbances (nausea, diarrhea).
  • Hypersensitivity reactions (angioedema, rash).
  • Palpitations (isolated reports).

1. Contraindications:
   • Hypersensitivity to loratadine, desloratadine, or components.
2. Pregnancy/Lactation:
   • BNF Category: Use only if benefits outweigh risks (limited human data).
   • Excreted in breast milk; avoid during lactation.
3. Hepatic Impairment: Dose adjustment required (see above).
4. Activities Requiring Alertness: Caution when driving or operating machinery.

Loratadine, metabolized by CYP3A4/2D6, interacts with:

• CYP3A4 Inhibitors (e.g., ketoconazole, erythromycin): Increase loratadine levels (monitor for side effects).
• CYP2D6 Inhibitors (e.g., fluoxetine, quinidine): May elevate plasma concentrations.
• Alcohol: No significant interaction, but avoid excess (Lange).

Central Nervous System Depressants: Minimal additive sedation

• Generic: Loratadine.
• Brand Names:
  • UK: Clarityn®, Alavert®.
  • US: Claritin®, Alavert®.

Others: Lisino® (India), Lorfast® (Europe).