Fexofenadine

Fexofenadine is a second‑generation oral antihistamine used to treat symptoms of seasonal allergic rhinitis and chronic idiopathic urticaria (hives). It is marketed in several countries under brand names such as Allegra and in generic forms. Compared with first‑generation antihistamines, fexofenadine causes less sedation because it has limited penetration of the blood–brain barrier.

Pharmacology and mechanism of action: Fexofenadine selectively antagonizes peripheral histamine H1 receptors, reducing histamine‑driven symptoms such as nasal itching, sneezing, rhinorrhea, and itching associated with urticaria. It is a non‑sedating antihistamine, intended to minimize central nervous system effects.

Pharmacokinetics: The drug is taken by mouth and is absorbed with peak plasma levels typically reached within 1 to 3 hours. The elimination half‑life is about 14 hours in adults. Fexofenadine is largely excreted unchanged in urine and feces, with minimal hepatic metabolism. Absorption can be markedly reduced by fruit juice due to inhibition of intestinal transporters; it is advised to take the medication with water and avoid fruit juice within a few hours of dosing.

Interactions and cautions: Fruit juice (orange, apple, and other) can substantially decrease fexofenadine absorption; certain antacids containing aluminum or magnesium can also lower absorption. Dose adjustments may be needed in people with significant renal impairment. Caution is advised in individuals with severe kidney disease, older adults, and those with known hypersensitivity to the drug. Safety during pregnancy and breastfeeding is not fully established; use should be guided by a clinician.

Administration and forms: Available as tablets and oral suspension in various strengths. Dosing regimens vary by age and condition, with common adult regimens including 60 mg twice daily or 180 mg once daily, and different schedules for pediatric patients.