Figure 1.

(a) Simulated blood or saliva cotinine concentrations over time, assuming an initial concentration of 300 ng/ml, and different half-lives. The dashed line represents a nonsmoking cotinine level cutoff of 15 ng/ml. Cutoff would be reached at 130, 70, and 35 hours if cotinine half-life was 30, 16, and 8 hours, respectively. (b) Similar simulation to (a) but starting from a baseline cotinine level of 100 ng/ml. Cutoff would be reached at 83, 44, and 22 hours if cotinine half-life was 30, 16, and 8 hours, respectively. Reprinted with permission from Benowitz N, Jacob P, Ahijevych K, et al. Biochemical verification of tobacco use and cessation. Nicotine and Tobacco Research. 2002; 4:149–159.