Novel approaches to treating nicotine dependence remain a priority. The transdermal nicotine patch is the most widely used form of tobacco dependence treatment, but only ~1 in 5 smokers who use this treatment achieve cessation. One factor that may contribute to a poor response to transdermal nicotine is inter-individual variability in the rate of nicotine metabolism, which can be measured in saliva by the ratio of 3'hydroxycotinine (3-HC) to its precursor cotinine.