====== Loratadine ======

===== Classification =====
  * Second-Generation H1 Antihistamine
  * Peripheral H1 receptor inverse agonist

Parent class: [[allergy:histamine|Histamine & Antihistamines]]

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===== Mechanism of Action =====

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.

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===== Pharmacokinetics =====

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

Avoid strong CYP3A4 inhibitors in high-risk patients.

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===== Indications =====

  * [[allergy:clinical:allergic_rhinitis|Allergic Rhinitis]]
  * Chronic idiopathic urticaria
  * Seasonal allergies
  * Mild allergic symptoms

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

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===== Dosing (Adult) =====

  * 10 mg PO once daily

Pediatric dosing varies by age and weight.

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===== Adverse Effects =====

Generally well tolerated.

Possible:
  * Mild headache
  * Dry mouth
  * Fatigue (rare)

Minimal sedation compared to first-generation antihistamines.

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===== Contraindications / Cautions =====

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

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===== Drug Interactions =====

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

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===== Clinical Pearls =====

  * 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.

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===== Comparison Within Class =====

^ Drug ^ Sedation Risk ^ Duration ^ Notes ^
| [[allergy:drugs:loratadine|Loratadine]] | Very low | 24 hr | Active metabolite (desloratadine) |
| [[allergy:drugs:cetirizine|Cetirizine]] | Low | 24 hr | Slightly more sedating |
| [[allergy:drugs:fexofenadine|Fexofenadine]] | Minimal | 24 hr | Least sedating |

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===== Related Pages =====

  * [[allergy:histamine|Histamine & Antihistamines]]
  * [[allergy:clinical:allergic_rhinitis|Allergic Rhinitis – Stepwise Therapy]]
  * [[allergy:clinical:urticaria_angioedema|Urticaria & Angioedema]]