Trade name Allegra

Pregnancy category AU: B2

Routes of administration By mouth

Drug class Antihistamine; H1 receptor antagonist

Bioavailability 30–41%

Protein binding 60–70%

Metabolism Hepatic (≤5% of dose)

Elimination half-life 14.4 hours

Excretion Feces (~80%) and urine (~10%) as unchanged drug

An antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.

It is a selective peripheral H1 blocker. 

It 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.

Fexofenadine is used for relief from physical symptoms associated with seasonal allergic rhinitis and for treatment of chronic urticaria.

It does not cure, but prevents the symptoms of allergic rhinitis and chronic idiopathic urticaria: reducing the severity of the symptoms associated with those conditions, providing relief from repeated sneezing, runny nose, itchy eyes or skin, and general body fatigue. 

It is a safe drug to use for individuals with inherited long QT syndrome.

For the treatment of allergic rhinitis, fexofenadine is similarly effective to cetirizine, but is associated with less drowsiness than cetirizine.

Fexofenadine was also shown to inhibit histamine-induced wheal and flare to a significantly greater degree than loratadine or desloratadine,but slightly less effective than levocetirizine.

Fexofenadine at doses above 120 mg a day does not appear to provide additional efficacy in the treatment of allergic rhinitis.

The most common side effects include: headache, back and muscle pain, miosis or pinpoint pupils, nausea, drowsiness, and menstrual cramps. 

Anxiety and insomnia are rare.

The most common side effects were cough, upper respiratory tract infection, fever, and otitis media for children ages 6 to 11 and fatigue for children ages 6 months to 5 years.

No cardiovascular or sedative effects have been shown to occur even when taking 10 times the recommended dose.

Fexofenadine is a selective peripheral H1 receptor antagonist, and 

prevents the activation of the H1 receptors by histamine, preventing the symptoms associated with allergies from occurring. 

It does not readily cross the blood–brain barrier, so is less likely to cause drowsiness in comparison to other antihistamines that readily cross that barrier as first-generation antihistamines such as diphenhydramine.

Fexofenadine takes about an hour to take effect, affected by the choice of dosage form and the presence of certain foods.

It exhibits no anticholinergic, antidopaminergic, alpha 1-adrenergic, or beta-adrenergic receptor-blocking effects.

After oral intake, maximum plasma concentrations are reached after 2–3 hours. 

Fexofenadine should not be taken with a high-fat meal, as mean concentrations of fexofenadine in the bloodstream are seen to be reduced from 20 to 60% depending on form of medication.

Distribution: Fexofenadine is 60–70% bound to plasma proteins, mostly albumin.

Fexofenadine is a substrate of CYP3A4, but only about 5% is metabolized by the liver, indicating that hepatic metabolism is relatively minor in clearance from the body.

Most of the substance is eliminated unchanged via the feces (80%) and urine (11–12%).

Taking erythromycin or ketoconazole while taking fexofenadine increases plasma levels of fexofenadine.

Both erythromycin and ketoconazole are inhibitors of p-gp, a transporter protein involved in preventing the intestinal absorption of fexofenadine. 

When p-gp is inhibited, fexofenadine may be better absorbed by the body, increasing its plasma concentration.

Fexofenadine should be taken with water, and not to be taken with apple, orange, or grapefruit juice because they could decrease absorption of the drug. 

Grapefruit juice can significantly reduce the plasma concentration of fexofenadine.

Antacids containing aluminum or magnesium should not be taken within 15 minutes of fexofenadine, as they reduce its absorption by almost 50%: due to the formation of metal complexes with charged/polar moieties on fexofenadine. 

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