Compared with second-generation H1 blockers, first-generation H1 blockers have greater CNS penetration and more CNS side effects.

Compared with second-generation H1 blockers, first-generation H1 blockers have greater CNS penetration and more CNS side effects.

• A. They have greater CNS penetration and more CNS side effects
• B. They have greater CNS penetration but fewer side effects
• C. They have less CNS penetration
• D. They have the same CNS penetration

Answer: (A)

First-generation H1 blockers cross into the brain readily because they’re more lipophilic and less restricted by brain barriers. Once they reach central H1 receptors, they produce sedation and cognitive effects, along with anticholinergic CNS effects like confusion, especially in susceptible individuals. Second-generation H1 blockers, on the other hand, are designed to minimize brain entry—they’re more polar or are pumped out of the brain by transporters—so central H1 blockade is limited. This yields far less sedation and fewer CNS side effects while still treating peripheral allergic symptoms. So, the statement that first-generation agents have greater CNS penetration and more CNS side effects compared with second-generation agents is correct.

First-generation H1 blockers cross into the brain readily because they’re more lipophilic and less restricted by brain barriers. Once they reach central H1 receptors, they produce sedation and cognitive effects, along with anticholinergic CNS effects like confusion, especially in susceptible individuals. Second-generation H1 blockers, on the other hand, are designed to minimize brain entry—they’re more polar or are pumped out of the brain by transporters—so central H1 blockade is limited. This yields far less sedation and fewer CNS side effects while still treating peripheral allergic symptoms. So, the statement that first-generation agents have greater CNS penetration and more CNS side effects compared with second-generation agents is correct.