How fexofenadine works
Fexofenadine acts as a selective inhibitor of docking sites of the body’s own messenger substance histamine – the so-called histamine H1 receptors. In this way, the active ingredient prevents allergic reactions.
The messenger substance histamine has a variety of functions in the body. For example, it serves as a messenger between nerve cells in the brain (neurotransmitter) and as a regulator of gastric acid production, the feeling of hunger and thirst, body temperature and blood pressure. In addition, histamine has an allergy-mediating effect:
In the case of an allergy, the immune system reacts excessively to external influences that are actually harmless, such as plant pollen, animal hair or certain foods. Upon contact with the respective allergen (e.g. birch pollen, cat hair, peanuts), certain defense cells – the mast cells – release histamine.
This immediately triggers an inflammatory reaction. The affected tissue is supplied with more blood, reddens, swells and itches, the nose runs and the eyes water.
Antihistamines are used to relieve such allergic symptoms. They occupy the receptors of the messenger substance histamine so that it can no longer bind. The histamine released by the mast cells on contact with the allergen can therefore not trigger an inflammatory reaction.
Since fexofenadine does not cross the blood-brain barrier, it causes fatigue and drowsiness as side effects much less frequently than older antihistamines.
Absorption, breakdown and excretion
After its ingestion, fexofenadine is rapidly absorbed in the intestine and reaches its highest levels in the blood after about one to three hours. It is hardly broken down or metabolized. After 11 to 15 hours, about half of the antiallergic drug is mostly excreted in the stool through the bile.
When is fexofenadine used?
Fexofenadine is used to treat:
- hay fever (allergic rhinitis)
- hives (urticaria)
The duration of use and dosage depend on the type and severity of the condition. For seasonal symptoms such as hay fever, fexofenadine is taken for the duration of the pollen season.
How fexofenadine is used
The active ingredient is taken in tablet form, usually once a day before a meal with a glass of water.
For the treatment of hives, 180 milligrams of fexofenadine once a day is often prescribed. For symptom relief of hay fever, adolescents over twelve years of age and adults are given 120 milligrams of fexofenadine per day.
Lower-dose medicines are available for children six years of age and older.
The duration of use is determined in consultation with the doctor.
What are the side effects of fexofenadine?
Side effects commonly occur during treatment with fexofenadine in the form of headache, drowsiness, dizziness, nausea, and dry mouth.
One in one hundred to one thousand people treated also complain of symptoms such as fatigue, insomnia or sleep disturbances, nervousness, and nightmares.
What should I watch for while taking fexofenadine?
Drug interactions
Anti-heartburn agents that bind excess acid directly in the stomach (such as aluminum and magnesium hydroxide) should be taken at least two hours apart from fexofenadine, as they may interfere with the absorption of the anti-allergic in the intestine.
Fexofenadine must be discontinued at least three days before a scheduled allergy test to avoid confounding the results.
Driving and operating machinery
At the beginning of treatment with fexofenadine, heavy machinery should not be operated and motor vehicles should not be driven because of the risk of drowsiness and concentration problems. Patients should first monitor their individual response to the allergy medication.
Age Limitation
Fexofenadine is contraindicated in children under six years of age because the drug has not been studied in this age group.
Pregnancy and Lactation
Due to a lack of data, fexofenadine should not be taken during pregnancy. However, data from prescription studies to date show no evidence of adverse effects.
How to obtain medication with fexofenadine
In contrast to other European countries such as Austria and Switzerland, and also the Netherlands, fexofenadine is available in Germany only by prescription from pharmacies.
How long has fexofenadine been known?
The precursor terfenadine, which was developed in the early 1970s and marketed in 1982, came into severe disrepute from 1993 onwards: it was discovered that it can trigger severe cardiac arrhythmias. As a result, terfenadine is no longer approved in many countries.
Research finally showed that fexofenadine – a degradation product of terfenadine – has comparable effects to the original active ingredient, but does not cause any side effects on the heart. This was eventually confirmed in clinical trials. In 1997, fexofenadine was therefore approved for the treatment of allergies.
