08-31-2014, 03:33 AM
It does make some people a little drowsy, but not like Benadryl. It is a second generation antihistamine whereas Benadryl is a 1st generation. The first generation ones cross the brain blood barrier more freely than second generation, and that is what makes you drowsy. The active ingredient in Benadryl is actually the same drug in Tylenol PM. I take a Zyrtec every morning with my breakfast and it doesn't cause me any problems.
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