The key difference between the first and second generation antihistamines is that:

Question

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The key difference between the first and second generation antihistamines is that the first generation antihistamines are more lipophilic and therefore cross the blood-brain barrier (BBB) causing central nervous system effects. Second generation medications have been developed to be less lipophilic, and as a result, they do not cross the BBB to the same extent, resulting in fewer central nervous system side effects. Choice A is incorrect because it is actually the second generation antihistamines that require lower dosages for the same therapeutic effect. Choice B is incorrect because second generation medications are typically associated with fewer undesirable side effects than first generation antihistamines. Choice D is incorrect because the first generation antihistamines are actually more lipophilic, not less.

The Key Difference Between the First and Second Generation Antihistamines