albumin allows binding of drug which usually means the drug will stay in the plasma not enter tissue spaces and therefore not allow for a response to happen. during disease albumin levels will vary so you must take this in.
if you have lower albumin levels in ur plasma then higher concentrations of drug will be free to move around into tissues and cause affects
because there is an ever so slight but still a difference between the pH level of maternal and foetal circulations and so this means that drug perscribed and given to the mother could accumulate on the foetal side of circulation which favours it becoming ionised then it cant move and the drug is stuck within the foetal circulation leading to foetal toxicity
when thinking about body fluid volumes you must think about how many Litres of fluid is available in the region to which you are inserting the drug to go to as you will have to dose accordingly if it is able to diffuse through from extracellular to intracellular etc
not all drugs go to body fluid volumes some go to adipose tissue,hair,bone etc etc so actually sampling from plasma is not going to give an accurate representation of how much drug is actually there this is why we VoD (volume of distribution) is physiologically not possible so we call it apparent volume of distruibution