Fexofenadine
Fexofenadine is a second-generation H1 antihistamine used in adults and children for allergic rhinitis and urticaria. It is the active metabolite of terfenadine and produces minimal central nervous system penetration with no clinically relevant sedation.
- Chemical formula
- C32H39NO4
- CAS number
- 83799-24-0
- ATC code
- R06AX26
- Molecular weight
- 501.66 g/mol
- Drug class
- Second-generation H1 antihistamine
- Also known as
- MDL 16455, Fexofenadina
What is it?
Fexofenadine was approved in the late 1990s as the active metabolite of terfenadine, an earlier antihistamine withdrawn because of cardiac arrhythmia risk. Unlike terfenadine, fexofenadine does not undergo extensive cytochrome metabolism and lacks the cardiac safety concerns of its predecessor. It is supplied as oral tablets and oral suspension and is dispensed both with and without prescription depending on the market and the dose.
Mechanism of action
Fexofenadine selectively blocks peripheral H1 histamine receptors, antagonising the effects of histamine on vasodilation, capillary permeability, sensory nerve endings and smooth muscle. Its very low penetration of the blood-brain barrier accounts for the absence of clinically relevant sedation. The drug also lacks anticholinergic effects at standard doses. It is a substrate of P-glycoprotein and certain organic anion-transporting polypeptides, which is the basis of some food and drug interactions.
Pharmacokinetics
Fexofenadine is absorbed orally with peak plasma concentrations reached after one to three hours. The drug is excreted predominantly unchanged, with a small fraction undergoing hepatic metabolism. Plasma protein binding is approximately 60% to 70%. The terminal half-life is approximately 14 hours, supporting once or twice-daily dosing. Bioavailability is reduced by fruit juices such as orange, grapefruit or apple juice, which inhibit organic anion-transporting polypeptides.
Indications
Fexofenadine is approved in adults and children for the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria. According to international guidelines, it is one of the recommended second-generation antihistamines for first-line treatment of these conditions, particularly when minimal sedation is required, including in commercial drivers and other safety-critical occupations. Fexofenadine is not the first-line treatment for severe asthma or anaphylaxis.
Safety profile
Fexofenadine is very well tolerated. Common adverse effects are mild headache, nausea and dizziness. Sedation is rare at standard doses. The drug has no clinically significant cardiac effects in routine use. According to the prescribing information, dose adjustment may be needed in significant renal impairment. Drug-food interactions reduce bioavailability when fexofenadine is taken with fruit juices, which is why it is recommended to take the medication with water.
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Frequently asked questions
How is fexofenadine different from cetirizine and loratadine? ▾
All three are second-generation antihistamines, but fexofenadine has the lowest reported sedation profile of the three and is often preferred when sedation must be minimised. Cetirizine has slightly more sedation and a faster onset, while loratadine has minimal sedation and a long half-life. The choice between them is often a matter of individual response. According to international guidelines, all three are recommended first-line options.
Why should fexofenadine not be taken with fruit juice? ▾
Fruit juices such as orange, grapefruit and apple juice inhibit the intestinal organic anion-transporting polypeptides that absorb fexofenadine, which can reduce bioavailability by up to 60%. This may diminish clinical effect. According to the prescribing information, fexofenadine should be taken with water rather than juice, with a recommended interval of several hours from juice consumption.
Does fexofenadine cause cardiac arrhythmia? ▾
No. Fexofenadine is the active metabolite of terfenadine, but unlike terfenadine it does not block cardiac potassium channels and does not prolong the QT interval at therapeutic concentrations. This is one of the reasons terfenadine was replaced by fexofenadine in clinical practice. According to the prescribing information, no specific cardiac monitoring is required at standard doses.
Can children take fexofenadine? ▾
Yes, in age- and weight-based dosing. Fexofenadine is approved in children from age six in some markets and from age two in others, with paediatric formulations and dose schedules defined in the prescribing information. According to clinical guidelines, paediatric prescribing should be discussed with a paediatrician or pharmacist, particularly in chronic conditions or in young children with renal impairment.
What are the main contraindications for fexofenadine? ▾
Fexofenadine is contraindicated in known hypersensitivity to the molecule or its excipients. Caution is required in significant renal impairment, where dose adjustment may be needed, and in pregnancy and breastfeeding, where data are limited. According to the prescribing information, the medical history and current medication list must be reviewed by a clinician before any prescription, particularly when other allergy or CNS-active medications are already being taken.
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