DOXAFIN 5MG FILM COATED TABLETS

Indications

• Allergic rhinitis
• Seasonal allergic rhinitis
• Perennial allergic rhinitis
• Chronic idiopathic urticaria

Dosage

Children: For children aged 6 to 11 years, the usual dose is 2.5 mg once daily. For children aged 12 years and older, the usual dose is 5 mg once daily. Refer to the BNF for Children for more detailed dosing.

Adults: The usual adult dose is 5 mg once daily.

Mechanism of action

Desloratadine competes with free histamine for binding at H1-receptors found in the gastrointestinal tract, uterus, large blood vessels, and bronchial smooth muscle. By blocking these receptors, it inhibits the physiological actions of histamine, leading to a reduction in symptoms such as nasal congestion and watery eyes associated with allergic reactions.

Pharmacodynamics

Desloratadine exhibits a selective and peripheral action as an H1-receptor antagonist. It mitigates the effects of histamine, a chemical released during allergic reactions that causes symptoms like swelling and irritation. By preventing histamine from activating H1 receptors, Desloratadine effectively alleviates allergic symptoms without penetrating the central nervous system, thus avoiding sedation.

Pharmacokinetics

Desloratadine is well absorbed and reaches peak plasma concentrations within 3 to 4 hours after oral administration. It has a long half-life, allowing for once-daily dosing. The drug is primarily metabolized in the liver, and its metabolites are excreted via urine and feces. It does not significantly interact with the cytochrome P450 enzyme system, which reduces the potential for drug interactions.

Adverse effects

• dry mouth
• fatigue
• dizziness
• nausea

Precautions

• Caution in patients with severe hepatic impairment
• Use with caution in individuals with a known hypersensitivity to desloratadine or any of its components

Pregnancy

Desloratadine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Consult healthcare professionals for guidance.

Breast-feeding

Desloratadine is excreted in human milk, thus caution should be exercised when administered to nursing mothers.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• tablets
• oral solution

Mechanism of action

Like other H1-blockers, Desloratadine competes with free histamine for binding at H₁-receptors in the GI tract, uterus, large blood vessels, and bronchial smooth muscle. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms (eg. nasal congestion, watery eyes) brought on by histamine.

Pharmacodynamics

Desloratadine is a long-acting second-generation H₁-receptor antagonist which has a selective and peripheral H1-antagonist action. Histamine is a chemical that causes many of the signs that are part of allergic reactions, such as the swelling of tissues. Histamine is released from histamine-storing cells (mast cells) and attaches to other cells that have receptors for histamine. The attachment of the histamine to the receptors causes the cell to be "activated," releasing other chemicals which produce the effects that we associate with allergies. Desloratadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of cells by histamine. Unlike most other antihistamines, Desloratadine does not enter the brain from the blood and, therefore, does not cause drowsiness.