i believe it does work. but the reason why is that the extra water allows the medicine to be absorbed into the blood faster when its mixed with the water.
water soluble medicines and vitamins are more likely to be absorbed if there is sufficient water to absorb it. medicine or vitamins not absorbed pass out into the waste , unused, via natural body processes.
(undigested and unabsorbed materials in your stomach can also cause irritation nausea etc.)
this i why most doctors will tell you to take your medicine with water.
this is how i understand it at any rate.
keep your mind from this way of enquiry, for never will you show that not-being is
~parmenides