Drugs interference maybe of two types:

1. physiologic (In vitro)

2. during analysis of metabolite of interests (In vivo) 

-Effects of oral contraceptives:

↑ ceruloplasmin,thyroxine binding globulin (TBG)

transferrin, iron, TAG

↑ alanine amino transferase ( ALT) and

γ glutamyl transferase (GGT)

↓ albumin

-Hepatotoxic drugs

-Diuretics