more stringent definition (mean D0-cotinine > 20 ng/ml). Subject characteristics are summarized in Supplemental Table 1. All subjects were requested not to consume food, and especially grapefruit and grapefruit juice, for 12h prior to their visit. Subjects were not asked to abstain from smoking except between their arrival and the first blood draw, 30 minutes after D2-nicotine administration. The time of last cigarette smoked was recorded for each subject.
