Description

Desloratadine is a second-generation, non-sedating antihistamine. It is the active metabolite of loratadine and is known for its long duration of action. Desloratadine selectively blocks peripheral histamine H1 receptors and does not cause significant drowsiness because it does not readily cross the blood-brain barrier. It is available as oral tablets, orally disintegrating tablets, and oral syrup.

Indication

Desloratadine is indicated for the relief of symptoms associated with various allergic conditions in adults and children:

• Seasonal Allergic Rhinitis: It is used to treat symptoms of hay fever, such as sneezing, runny nose, nasal itching, itchy or watery eyes, and itching of the palate.

• Perennial Allergic Rhinitis: It is also effective for managing symptoms of year-round allergies.

• Chronic Idiopathic Urticaria (Hives): It is used to relieve the itching and reduce the size and number of hives associated with this skin condition.

Mechanism of Action

Desloratadine’s mechanism of action is based on its ability to block the effects of histamine, a key mediator of allergic reactions. The process is as follows:

1. Histamine Release: During an allergic reaction, allergens trigger the release of histamine from mast cells in the body.

2. H1 Receptor Antagonism: Histamine binds to and activates H1 receptors on cells, leading to the characteristic symptoms of an allergy. Desloratadine is a potent and selective peripheral H1 receptor antagonist. This means it binds to H1 receptors on cells outside the central nervous system, preventing histamine from binding to them.
3. Symptom Relief: By blocking the H1 receptors, desloratadine prevents the effects of histamine, such as vasodilation, increased vascular permeability, and itching. This action provides relief from allergic symptoms like sneezing, rhinorrhea, and urticaria without causing significant sedation, as it has a low affinity for H1 receptors in the brain.

4. Anti-inflammatory Effects: In addition to its antihistaminic properties, desloratadine has also been shown to have anti-inflammatory effects by inhibiting the release of pro-inflammatory cytokines and chemokines from mast cells and basophils. This contributes to its overall effectiveness in treating allergic rhinitis and urticaria.