Fexofenadine is a second-generation, non-sedating, selective peripheral H1-receptor antagonist (antihistamine). It is the active metabolite of terfenadine. It is widely used for the symptomatic relief of allergic conditions without the central nervous system depressant effects common to first-generation antihistamines. It does not cross the blood-brain barrier significantly.
Adult: 180 mg once daily. For Allergic Rhinitis, 60 mg twice daily is also an approved regimen.
Note: Take with a full glass of plain water. Do not take with fruit juices (apple, orange, grapefruit) or antacids containing aluminum and magnesium hydroxide, as they significantly reduce absorption. Can be taken with or without food, but consistency is advised.
Fexofenadine competitively and selectively inhibits the histamine H1-receptor on surfaces of effector cells (e.g., in respiratory tract, blood vessels, gastrointestinal tract). This blockade prevents histamine-mediated allergic responses such as vasodilation, increased vascular permeability, and smooth muscle contraction.
Pregnancy: Category C (US FDA). Animal studies have shown adverse effects. There are no adequate and well-controlled studies in pregnant women. Use only if potential benefit justifies potential risk to the fetus. Consult physician.
Driving: Fexofenadine is classified as a non-sedating antihistamine. At recommended doses, it generally does not impair driving ability. However, individuals should monitor their own response, as drowsiness can occur in some.
| Erythromycin, Ketoconazole | May increase plasma concentration of fexofenadine, but no clinically significant increase in adverse events or QT prolongation observed at recommended doses. | Moderate |
| Aluminum & Magnesium containing Antacids (e.g., Magaldrate) | Markedly decrease fexofenadine absorption and bioavailability. Administer antacids at least 2 hours before or after fexofenadine. | Major |
| Fruit Juices (Apple, Orange, Grapefruit) | Decrease absorption and bioavailability of fexofenadine by inhibiting OATP transporters. Avoid concurrent administration. | Major |
| Rifampicin | May decrease plasma levels of fexofenadine. | Moderate |