Why does 60mg pseudoephedrine work for merely 4 hours, when citerizine can work 24 hours?

(The pseudoephedrine is for decongestion and the citerizine is antihistamine). I can understand that a person's kidneys can filtrate a substance contained by his blood within 4 hours, but why next does it not filtrate out the citerizine in like time?Why does 60mg pseudoephedrine work for merely 4 hours, when citerizine can work 24 hours?
The reason is rooted contained by a phenomenon known as pharmacokinetics. Different drugs own different ways of staying longer (or shorter) in your body. A drug's pharmacokinetics depends on closely of complex factors resembling molecular size, binding to proteins in our system, affinities, and other mechanism. It is also the reason why some drugs are given single once daily while others necessitate repeated dosings per day (i.e. 3x/day, etc.)
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