Fexofenadine hydrochloride (Allegra) is an antihistamine drug used in the treatment of hayfever and similar allergy symptoms.
It was developed as a successor of and 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 used to treat the symptoms of seasonal allergies (hay fever) in adults and children. Fexofenadine is also used to treat skin itching and hives caused by a condition called chronic idiopathic urticaria in adults and children.
Fexofenadine may also be used for purposes not listed in this medication guide.
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.
Like other H1-blockers, 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.
Metabolism: Approximately 5% of the total dose is metabolized, by cytochrome P450 3A4 and by intestinal microflora.
Absorption: 33%
Route of elimination: N/A
Half life: 14.4 hours
All medicines may cause side effects, but many people have no, or minor, side effects.Some medical conditions may interact with Fexofenadine.
Tell your doctor or pharmacist if you have any medical conditions.
Side effects include dizziness, drowsiness, and dry mouth.
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.
