I personally feel using "presence or absence" gives it a positive connotation followed by the negative one - 

in the manner of saying "plus or minus" or "+/-" 

In your example, does it mean that the [parameter] was measured in both presence and absence of [drug name] - i.e. twice?

If not it would depend on which is more relevant for the point you're proving - i.e. does the presence of [drug] matter more than the absence? 

It seems to be 2 different opposing results to me, but that could be my lack of pharmaceutical context.