Antihistamine · Corticosteroid
Also known as Fexofenadine Hydrochloride, Allegra, Telfast
KDIGO 2024 + manufacturer label
742 branded formulations and 11 fixed-dose combinations. Look up specific brands in the Drugs workspace.
Jan Aushadhi — generic available at GoI pharmacies
Fexofenadine is a second-generation selective histamine H1-receptor antagonist. It competes with histamine for binding to H1 receptors on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract, preventing histamine-mediated allergic responses (vasodilation, increased vascular permeability, smooth muscle contraction, itching). Unlike first-generation antihistamines, fexofenadine has minimal penetration of the blood-brain barrier due to active efflux by P-glycoprotein (MDR1) transporters at the blood-brain barrier, resulting in negligible sedation and anticholinergic effects. It is the active carboxylic acid metabolite of terfenadine (which was withdrawn due to QT prolongation).
FDA PLLR: Animal studies showed no teratogenicity at doses up to 3x MRHD. Limited human data. Generally considered safe in pregnancy. Recommended as first-line antihistamine in pregnancy by ACOG.
Excreted in breast milk in very low concentrations. Minimal systemic exposure in nursing infant due to poor oral bioavailability. Compatible with breastfeeding per AAP.
Decreased plasma concentrations of fexofenadine, potentially leading to reduced efficacy.
Administer fexofenadine at least 2 hours before or 2 hours after antacids containing aluminum or magnesium.
Source: DDInter
Increased fexofenadine exposure, potentially leading to increased side effects.
Monitor for increased fexofenadine effects.
Reduced fexofenadine efficacy.
Separate administration by at least 2 hours.
May result in decreased exposure to medications that are substrates of UGT, Pgp, BCRP, or OATP1B1 (e.g., fexofenadine, rosuvastatin).
Monitor for reduced efficacy of these medications. Dose adjustment or alternative agents may be necessary.
Source: DDInter
Increased fexofenadine exposure, potentially leading to increased side effects.
Monitor for increased fexofenadine effects.
Erythromycin inhibits P-gp and OATP transporters, increasing fexofenadine plasma levels by 60-80%.
Monitor for increased antihistamine side effects. No dose adjustment typically needed but be aware of potential interaction.
Source: Kimi deep-research + Cla
Antacids containing aluminum and magnesium reduce fexofenadine absorption by binding/chelating the drug in the GI tract.
Separate administration by at least 2 hours. Give fexofenadine 2 hours before or after antacids.
Source: Kimi deep-research + Cla
Fruit juices inhibit intestinal OATP transporters (OATP1A2 and OATP2B1) that mediate fexofenadine absorption, reducing bioavailability by ~40%.
Take fexofenadine with WATER only. Avoid fruit juices within 4 hours of dosing. This is a critical counseling point.
Source: Kimi deep-research + Cla
Decreased plasma concentrations of fexofenadine, potentially leading to reduced efficacy.
Advise patients to avoid taking fexofenadine with fruit juices. Take fexofenadine with water.
P-glycoprotein inhibitors increase fexofenadine plasma levels by blocking its efflux from intestinal enterocytes and renal tubular cells.
Monitor for increased side effects (headache, drowsiness). May need to reduce fexofenadine dose if used concurrently with strong P-gp inhibitors.
Source: Kimi deep-research + Cla
Decreased plasma concentrations of fexofenadine, potentially leading to reduced efficacy.
Administer fexofenadine at least 2 hours before or 2 hours after antacids containing aluminum or magnesium.
Source: DDInter
Rifampin induces P-glycoprotein, reducing fexofenadine absorption and plasma levels, potentially causing loss of efficacy.
Monitor for reduced antihistamine efficacy. May need to increase fexofenadine dose or switch to alternative antihistamine.
Source: Kimi deep-research + Cla
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e, Katzung, BNF·Verified: 2026-05-18 · House clinical team·Cockpit curated: 2026-05-18