What is the main consequence of using hydroxyzine as an H1 receptor antagonist?

Hydroxyzine is classified as a first-generation antihistamine, which means it readily crosses the blood-brain barrier and exerts effects on the central nervous system (CNS). This ability to penetrate the CNS is a key characteristic of first-generation antihistamines, leading to sedative effects. Hydroxyzine is often used in the treatment of anxiety, as well as for its antihistaminic properties in allergy treatment. Its sedative effects can make it beneficial in certain scenarios, but they also raise the potential for drowsiness, which is a common side effect associated with its use.

The other options do not accurately reflect the properties of hydroxyzine. It does indeed affect the blood-brain barrier due to its first-generation status, which enables sedation. While hydroxyzine does have some therapeutic applications, it is not free from side effects; sedation is one of the most common adverse effects noted. Finally, it is not classified as a second-generation antihistamine; that classification applies to other agents that are less likely to penetrate the CNS, typically resulting in fewer sedative effects.