Fexofenadine
H1 antihistamines
H1 antihistamines
The least sedating second-generation antihistamine; fruit juices and some antacids reduce its absorption.
Quick facts
- Group
- H1 antihistamines
- Target
- Histamine H1 receptor
- Used for
- Seasonal allergic rhinitis · Chronic hives
- Key effects
- Headache · Nausea or indigestion · Dizziness
- Monitor
- Symptom relief
- ATC
- R06AX26
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows desloratadine bound to the human histamine H1 receptor (cryo-electron microscopy); fexofenadine binds the same site.
Fexofenadine is the active metabolite of terfenadine, an older antihistamine withdrawn because it prolonged the QT interval. Fexofenadine keeps the peripheral H1 inverse agonism without that cardiac effect. It is a substrate of P-glycoprotein, which keeps it out of the brain, so it causes essentially no sedation.
- Fexofenadine binds peripheral H1 receptors
- Histamine itch, sneezing and wheals are blocked
- P-glycoprotein pumps it out of the brain: no sedation
- It is not metabolised much and leaves in bile and urine
Indications
- Seasonal allergic rhinitis Allergic rhinitis →
- Chronic hives (urticaria) Urticaria and angioedema →
Adverse effects
Common
- Headache
- Nausea or indigestion
- Dizziness
Contraindications
- Hypersensitivity to fexofenadine
- Caution in kidney disease
Key interactions
- Fruit juices (grapefruit, orange, apple)
- Reduce absorption by blocking intestinal uptake transporters
- Antacids with aluminium or magnesium
- Reduce absorption; they are separated by a few hours
What is monitored
- Symptom relief
Administration and safety
- Swallowed with water, not with fruit juice
- Separated by a few hours from aluminium or magnesium antacids
- Combination tablets with pseudoephedrine exist
Pregnancy and breastfeeding
Human pregnancy data are fewer than for loratadine or cetirizine; use is decided with the clinician.
Nursing care
- Teach to take it with water and not with fruit juice
- Ask about antacids and space them apart
- Useful for people who must stay alert, such as drivers or pilots
Pharmacokinetics
- Absorption
- Oral; reduced by fruit juices (grapefruit, orange, apple) and by aluminium- or magnesium-containing antacids
- Metabolism
- Very little
- Elimination
- Mainly unchanged in faeces (bile) and some in urine
- Onset and duration
- Within a few hours
Test yourself
Think of the answer, then tap the question to see it.
Which older antihistamine is fexofenadine the active metabolite of, and why was that drug withdrawn?
Terfenadine; it prolonged the QT interval and caused arrhythmias.
Why should fexofenadine not be taken with orange or grapefruit juice?
The juices reduce its intestinal absorption and therefore its effect.
Why does fexofenadine cause almost no sedation?
P-glycoprotein pumps it out of the brain.
Connections
← Back to the class: H1 antihistamines
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Fexofenadine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Fexofenadine: antihistamine medicine that relieves allergy symptoms - NHS (NHS, 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.