I've been reading the British National Formulary 65 (BNF-65) and it mentioned that in some, especially at higher dosages, sedating (first-generation) antihistamines, can produce paradoxical excitatory (or stimulating) effects and so I felt like asking the age-old question, "Why?" because as I hope is obvious by my questions I am fascinated by drug action and I felt there was no better place to ask this question than here on biology stackexchange.
closed as too broad by WYSIWYG, Chris, GriffinEvo, Chris Stronks, The Last Word Dec 9 '14 at 10:09
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