Table 2.

Nicotine N-oxide as a molar percentage of nicotine and its metabolites in urine by C-oxidation and glucuronidation phenotype (study 1)

Phenotype*Quartile ratio valuesNMolar % of nicotine N-oxide mean (95% CI)
Cotinine glucuronide to cotinine
    Low<0.89276.8 (5.7-7.9)
    Average0.89-1.5546.1 (5.4-6.9)
    High>1.5275.5 (4.4-6.6)
Trans-3′-hydroxycotinine to cotinine
    Low<0.45258.7 (7.7-9.7)
    Average0.45-0.69526.1 (5.4-6.8)
    High>0.69254.3 (3.3-5.3)
  • *Phenotype was assessed by metabolite ratio: low, lowest quartile; average, interquartile range; high, highest quartile.

  • Cotinine glucuronide to free cotinine ratio quantified in first morning urine. Nicotine N-oxide means did not differ by phenotype. χ2 test for trend: P = 0.055.

  • Ratio of total trans-3′-hydroxycotinine to free cotinine quantified in plasma. Mean nicotine N-oxide values differed significantly within each phenotypic group with P-values < 0.005.