Understanding the blood brain barrier
UNDERSTANDING THE
BLOOD BRAIN BARRIER
Allevia 120mg is non-drowsy in the majority of people. This is because fexofenadine does not cross the blood brain barrier and thus is unlikely to cause drowsiness like some other antihistamines.1
Click on the boxes below to reveal how fexofenadine works without causing drowsiness:*
The blood brain barrier is a layer of specialised cells around the brain that protects it by controlling which molecules can pass from the blood to the brain.2,3
It also blocks most medicines, unless they are small lipid soluble molecules.3,4
First-generation ‘sedating’ antihistamines are highly lipid soluble and can cross the blood brain barrier where they block the release of histamine from histamine 1 receptors.5 This subsequently causes drowsiness and cognitive impairment.5
Second-generation ‘non-sedating’ antihistamines, like fexofenadine, are larger molecules and less fat soluble. Therefore they are less likely to cross the blood brain barrier.4,5 Compared to first-generation antihistamines, fexofenadine does not cross the blood brain barrier6 and therefore it does not cause drowsiness in the majority of people.1 It only binds to H1 receptors7,8 and consequently, fexofenadine is one of the least sedating second-generation antihistamines.1,7
This mode of action video visually demonstrates how fexofenadine is non-drowsy in the majority of people.
*In the majority of people