eli5 How does an antihistamine like Hydroxyzine lower anxiety?

Question

Hydroxyzine is approved to treat anxiety. What’s the mechanism that makes this work?

Can all first gen antihistamines do this?

In: Biology

Answer 1

First generation antihistamines cross the blood-brain barrier very easily. We have histamine receptors in our brain, specifically in our hypothalamus. These histamine receptors in the hypothalamus have a major role in our sleep-wake cycle. When they’re inhibited, we feel drowsy.

Anti anxiety medication is mostly just about relaxing the body. If you’re having an anxiety/panic attack, anti anxiety medication calms down all that extra activity. I would imagine that all first generation antihistamines have a certain amount of anti anxiety benefit, but hydroxyzine is the most successful. The anti anxiety is just a byproduct of the drowsiness, but some medications do it better than others.