03) and Asians (p = .01). Table 2. Nicotine Metabolite Ratio (NMR) and selleck products Participant Characteristics Gender The sample was 67.3% female. Males smoked more cigarettes per day than females (4.2 vs. 2.7; p = .04), but levels of cotinine were not significantly different (44.9 vs. 32.4ng/ml, respectively, p = .15). There was no difference in number of years since first cigarette smoked between males and females (1.5 vs. 1.5 years, p = .94) and scores on the mFTQ were similar between males and females (2.6 vs. 2.6, p = .93). There was no significant difference in NMR between males and females (p = .70; see Table 2). Influence of Hormones Stage of pubertal development was not associated with NMR for either boys (r = .05, p = .72) or girls (r = .13, p = .18).

With the exception of one, all females had started menstruation (mean age of onset = 12.3 years, SD = 1.4). There was no association with duration of years since the onset of menstruation and NMR (r = ?.07, p = .50). There was no significant difference in NMR between the 19 girls who reported using estrogen-containing contraceptives versus the 83 girls who did not (p = .24) or the 10 who used progestin-only contraceptives (p = .45). DISCUSSION Race In this study of adolescent smokers, we found similar racial differences in rates of nicotine metabolism as have been reported in adult smokers (Benowitz, Perez-Stable, Herrera, & Jacob, 2002; Hukkanen, Jacob, & Benowitz, 2005; Moolchan, Franken, & Jaszyna-Gasior, 2006; Perez-Stable et al., 1998).

Specifically, these studies showed that on average Whites have faster rates of nicotine metabolism than Blacks/African Americans, and Asians have the slowest rates of metabolism with Hispanics having rates similar to Whites. Similar findings were recently reported based on NMR derived from secondhand smoke nicotine exposure in young children (D. A. Dempsey et al., 2012). Much of the variability in nicotine metabolism can be attributed to variability in the enzymatic activity of CYP2A6, more than 50% of which is heritable (Swan et al., 2005). CYP2A6 is the primary enzyme responsible for the metabolism of nicotine (Messina, Tyndale, & Sellers, 1997). Factors that affect CYP2A6 activity include genetic polymorphisms, of which more than 90 have been identified and which occur in different frequencies among different racial/ethnic groups (Benowitz, Swan, Jacob, Lessov-Schlaggar, & Tyndale, 2006; ��CYP2A6 Allele Nomenclature��; Malaiyandi, Sellers, & Tyndale, 2005).

The differences we report in rates of metabolism between races are consistent with the known frequencies of CYP2A6 polymorphic alleles associated with absent Cilengitide or reduced enzymatic activity (Nakajima et al., 2006). Gender/Hormones Hormones, including estrogen, can affect CYP2A6 activity, explaining why adult women metabolize nicotine faster than men and why women taking estrogen-containing contraceptives metabolize nicotine even faster (Benowitz, Lessov-Schlaggar, et al., 2006).