I am not too sure, I vaguely remember from pharmacology class that some drugs take longer to break down and get released into your body so that could be one reason why certain drugs take longer to have an effect. I think Bernard would probably know the exact answer to this! 🙂
I think Sonia’s on to it! Each drug, depending on how it’s made, spends a different amount of time in the body. Some drugs which can dissolve in water spend less time in the body. Some drugs can have targeting molecules attached to them to help them work faster, as well. Bernard might have some good ideas on this question too!