Fexofenadine; Uses, Dosage, Side Effects, Interactions

Fexofenadine is a second generation, long-lasting selective histamine H1 receptor antagonist with the anti-inflammatory property. Fexofenadine is a highly selective and reversible competitor at peripheral H1 histamine receptors in the gastrointestinal (GI) tract, blood vessels, and bronchial smooth muscle. This agent interferes with mediators release from mast cells either by inhibiting calcium ion influx across mast cell/basophil plasma membrane or by inhibiting intracellular calcium ion release within the cells. In addition, fexofenadine may also inhibit the late-phase allergic reaction by acting on leukotrienes or prostaglandins, or by producing an anti-platelet activating factor effect. Overall, this agent blocks the actions of endogenous histamine, thereby leads to temporary relief of the negative symptoms associated with histamine and achieve effects such as decreased vascular permeability, reduction of pruritus and localized smooth muscle relaxation.

Fexofenadine hydrochloride (Allegra) is an antihistamine drug used in the treatment of hayfever and similar allergy symptoms. It was developed as a successor of an alternative to terfenadine. Fexofenadine, like other second and third-generation antihistamines, does not readily pass through the blood-brain barrier, and so causes less drowsiness than first-generation histamine-receptor antagonists.

Fexofenadine is classified as a second-generation antihistamine because it is less able to pass the blood-brain barrier and cause sedation, compared to first-generation antihistamines.

Mechanism of Action of Fexofenadine

Fexofenadine competes with free histamine for binding at H1-receptors in the GI tract, 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. Fexofenadine exhibits no anticholinergic, antidopaminergic, alpha1-adrenergic or beta-adrenergic-receptor blocking effects. Fexofenadine is a second-generation, long lasting H1-receptor antagonist (antihistamine) 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 allergy. Fexofenadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of cells by histamine. Unlike most other antihistamines, Fexofenadine does not enter the brain from the blood and, therefore, does not cause drowsiness. Fexofenadine lacks the cardiotoxic potential of terfenadine since it does not block the potassium channel involved in repolarization of cardiac cells.

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Indications of Fexofenadine

• Pollen allergy
• Seasonal allergic rhinitis
• Uncomplicated chronic idiopathic urticaria
• Runny nose
• Sneezing
• Itchy, watery eyes
• Itching of the nose or throat
• Treating hay fever (seasonal allergic rhinitis) in adults and children aged six years and over.
• Treating a long-term itchy nettle-type rash or hives (chronic idiopathic urticaria) in adults and adolescents aged 12 years and over.

Contra Indications of Fexofenadine

• kidney disease with reduction in kidney function

Allergies

• Antihistamines
• Antihistamines – Piperidine

Dosages of Fexofenadine

Strengths : 30mg, 60mg ,180mg Tablets