Quantitative concentrations of varenicline (ng/ml) were returned; with the Lower Limit of Quantitation for the analyses established at 1.00 ng/ml. Data Analysis Time selleck chem inhibitor to first smoking occasion following the lapse exposure was analyzed using a Cox regression survival model and end of study group abstinence rates were compared using a Chi-squared test. Measures of abstinence (continuous days of abstinence, percentage of abstinent participants, number of negative COT samples, and hours of abstinence) were based on COT-validated self-report and were analyzed using Fisher��s exact test (only p values are reported). All variables with multiple time points were analyzed using repeated measures regressions with an autoregressive (a) covariance structure in SAS PROC Mixed.

Pairwise comparisons between placebo and varenicline groups were conducted using planned comparison t tests at individual time points. A Cox regression survival model was used to assess the effects of possible moderators for abstinence duration following the lapse exposure (gender, race, education, FTND, CO and COT measures, cigarettes per day, and years of regular smoking). For the CPT, three missing values were interpolated as the median of that participant��s data at the lower and higher surrounding prices. The median number of cigarettes purchased across participants in each group was determined for each of the two time points (study Days 1 and 7), resulting in four median datasets. For each median dataset, values less than1 and all but the first (lowest price) instance of 1 within a set were eliminated because in logarithmic coordinates zero is undefined and small median values of 0.

5 and 1 provide little resolution. These four datasets were fit with nonlinear regression to the exponential equation by Hursh and Silberberg (2008): logQ=logQ0+k(e?��Q0C?1). The independent variable C represents cost (price per cigarette), the dependent variable Q represents consumption (cigarettes purchased at a particular GSK-3 price), and e is a constant known as Euler��s number. Scaling parameter k indicates the range of logQ and was set to 2 in this study because it was the lowest integer with an antilog (100) that covered the range of cigarettes purchased. Free parameters are Q0 (demand intensity) and �� (demand elasticity). Statistical comparisons among the four median datasets (pre and postinduction for both groups) were performed with an extra sum-of-squares F test using GraphPad Prism? v. 5.