I have seen lot of people sleep or say that they are feeling sleepy after taking some medicines. Why? I mean, if a medicine acts on some cell of the body because that cell has got its receptors and other cells have receptor for another part of that molecule, then too why do a large range of medicine induce sleep?
This also points to a doubt that there are only one kind of receptors for sleep inducing medicines (the real ones not the ones which have sleep as side effect) or many? If many are there, then it can be possible that a large range of medicines induce sleep.
Is it due to induction of sleep gives relaxation and thus give time for action of other medicines? Or is it just a natural process? If latter, why only some?
I don't want metabolism, just a reason.