Second/third-generation H1 antihistamine (terfenadine metabolite)
Fexofenadine is a non-sedating antihistamine, used to relieve the symptoms of allergic rhinitis (sneezing, runny nose, itchy eyes and nose) and urticaria. It does not cross into the brain, so it does not cause significant drowsiness. It is taken once a day.
Also known as: Telfast, fexofenadina, fexofenadine, Allegra
Fexofenadine + ketoconazole: increased fexofenadine exposure.
Fexofenadine is a P-glycoprotein (P-gp) substrate, and ketoconazole, by inhibiting this transporter, can raise fexofenadine concentrations. Although fexofenadine is a non-sedating antihistamine, high levels can cause drowsiness, headache or dizziness in susceptible patients. The interaction is generally mild; monitor symptoms and consider adjusting the antihistamine dose during antifungal treatment.
Ketoconazole + fexofenadine: the azole can raise fexofenadine levels (P-gp inhibition), with possible drowsiness. Monitor.
Ketoconazole interferes with intestinal fexofenadine transport (P-gp/OATP).
Antihistamine adverse effects.
Drowsiness, dizziness, nausea.
Watch for adverse effects; no relevant clinical impact for most patients.
DailyMed (FDA) — approved Fexofenadine label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=dd0da52b-fc82-4ec9-854c-0d7c52e926fb ; approved Ketoconazole label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f162e616-21b4-49b1-b437-15e21001a6f0 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Fexofenadine + erythromycin: increased fexofenadine exposure (OATP/P-gp transport).
Fexofenadine is eliminated essentially unchanged, without relevant CYP450 metabolism; the interaction with erythromycin occurs at the level of intestinal transporters (P-gp/OATP), which erythromycin inhibits, raising fexofenadine plasma concentrations. The mechanism is documented in the fexofenadine prescribing information (Allegra), which describes increased exposure with erythromycin coadministration (AUC increase of about 100%) without clinically relevant QT changes — unlike terfenadine (its precursor), fexofenadine does not prolong the QT interval. Erythromycin, in turn, "has been associated with prolongation of the QT interval and infrequent cases of arrhythmia" (erythromycin label). In practice, watch for fexofenadine adverse effects (headache, dizziness, mild somnolence) and, for erythromycin, respect the QT contraindications; routine dose adjustment is not needed, but avoid supratherapeutic doses.
Erythromycin + fexofenadine: erythromycin interferes with intestinal transport (P-gp/OATP) and raises fexofenadine levels. Watch for adverse effects (headache, dizziness).
Erythromycin interferes with intestinal transport (P-gp/OATP), raising fexofenadine levels.
Antihistamine adverse effects.
Nausea, dizziness, drowsiness.
Watch for adverse effects; not clinically significant for most.
DailyMed (FDA) — approved Fexofenadine label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=dd0da52b-fc82-4ec9-854c-0d7c52e926fb ; approved Erythromycin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0c05e1f7-a3d4-8e69-e063-6394a90aecc3 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Alcohol may potentiate drowsiness.
Limit alcohol intake.
EMC-UK (MHRA) — approved Fexofenadine SmPC: https://www.medicines.org.uk/emc/product/13208/smpc
Orange, apple and grapefruit juice reduce fexofenadine absorption (OATP inhibition).
Take fexofenadine with water and separate from fruit juices.
EMC-UK (MHRA) — approved Fexofenadine SmPC: https://www.medicines.org.uk/emc/product/13208/smpc
Fexofenadine is renally eliminated.
Recommended starting dose of 60 mg once daily in severe renal impairment.
EMC-UK (MHRA) — approved Fexofenadine SmPC: https://www.medicines.org.uk/emc/product/13208/smpc
Fexofenadine (terfenadine metabolite) showed no teratogenicity in available studies.
Can be used when indicated, at the lowest effective dose.
Limited breastfeeding data; consider an alternative with more data.
No specific additional contraception.
EMC-UK (MHRA) — approved Fexofenadine SmPC: https://www.medicines.org.uk/emc/product/13208/smpc
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Non-sedating H1 antihistamine (peripheral antagonist), available over-the-counter, indicated for the temporary relief of symptoms of hay fever and other upper respiratory allergies (runny nose, sneezing, itchy nose/throat, itchy and watery eyes). Does not cross the blood-brain barrier to a relevant degree — no sedation at recommended doses. Substrate of P-glycoprotein (P-gp).
Selective peripheral H1 histamine receptor antagonist, without relevant anticholinergic or sedative effects (does not significantly penetrate the CNS). Its pharmacokinetics depend on P-glycoprotein: P-gp mediates the absorption and excretion of the drug, and P-gp inhibition (e.g., piperine) increases its bioavailability.
Rapidly absorbed after oral administration, with peak plasma concentrations in about 1-3 hours; absolute bioavailability of approximately 33% (rapid absorption, Cmax within a few hours). Pharmacokinetics are linear up to 240 mg/day. Taking with fruit juices (grapefruit, orange, apple) may reduce absorption via OATP transporter inhibition.
Essentially not metabolised: about 95% of the dose is excreted unchanged (approximately 80% in faeces and 11-12% in urine). No relevant hepatic cytochrome P450 metabolism, which minimises metabolic interactions; elimination depends mainly on P-gp-mediated biliary/faecal excretion.
Mean elimination half-life of approximately 14.4 hours at 60 mg twice daily in healthy volunteers (allowing twice-daily dosing; at 120-180 mg the half-life is similar, about 11-15 hours). Renal impairment reduces clearance and prolongs the half-life.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
