Subjects were given 2 mg of [3′,3′-D2] nicotine (synthesized and purified to >99.4 % as described previously [21]) in 4 oz of juice, and blood was drawn approximately 30, 150, and 240 minutes later. This dose is well tolerated by non-smokers and results in measurable plasma nicotine concentrations[14]. All but 9 subjects were administered D2-nicotine prior to noon, the majority between 8 AM and 10 AM. The observed difference in plasma D2-cotinine at 30 min (Table 2) was not affected by the time of D2-nicotine administration. Plasma was collected and frozen at −20°C until analysis. The study complies with the Code of Ethics of the World Medical Association and obtained informed consent from participants and approval from the appropriate institutional review boards.
