Lerman and colleagues assessed 480 treatment-seeking smokers who were randomized to 8 weeks of transdermal nicotine or nicotine nasal spray. The nicotine metabolism ratio predicted the effectiveness of transdermal nicotine treatment at the end of treatment and at 6-month follow-up; however, the nicotine metabolite ratio was not a predictor of abstinence with use of nicotine nasal spray, presumably because smokers were able to titrate the dose of nasal spray based on differential metabolism (Lerman et al. 2006). The nicotine metabolite ratio was validated as a predictor of quitting success in an independent sample of smokers after 8 weeks of transdermal nicotine treatment (Schnoll et al. 2009). Based on these results, Lerman and others examined the efficacy of extended (6-month) transdermal nicotine therapy versus the standard 8-week therapy in 471 Caucasian smokers with either normal or reduced rates of nicotine metabolism. Reduced metabolizers were found to benefit more from extended therapy than standard 8-week therapy compared to normal metabolizers (Lerman et al. 2010).
