In addition, in an exploratory fashion, we will evaluate propofol pharmacogenetics. CYP2B6 and UGT1A9 are highly polymorphic enzyme responsible for the metabolism of propofol (20, 21). Novel allelic forms of CYP2B6 (22) and UGT1A9 (23) were identified recently that potentially could explain some of the large between patient variability in clearance resulting in large differences in propofol blood concentrations and responses to standard doses.