, 2006; Oncken et al., 2006). While the similarity in quit rates between the current study and previous reports may be simply coincidental, this observation lends credence to the validity of short-term models following of cessation and relapse as tools to evaluate and predict clinical effects of smoking cessation medications. Patterson et al. (2009) reported a similar relapse prevention effect of varenicline using an experimental model very similar to the one used here. In the present study, time to the first smoking episode following the experimental lapse exposure was about six days for placebo versus 14 days for varenicline (Table 2). These times are longer than those observed in the Patterson study, which were 2.6 versus 4.6 days for placebo and varenicline, respectively (among those receiving placebo first followed by varenicline).

However, the magnitude of the varenicline effect on relapse delay is roughly comparable across the studies, specifically a doubling in the time to relapse. Longer latencies to relapse in the present study are likely due to differences in the amount of abstinence-contingent payments, as well as the decelerating schedule of payments, which promoted early abstinence during the quit attempt. Also, there were differences in the expected duration of the quit attempt (1 week vs. 4 weeks), which may have influenced relapse likelihood. In contrast, Perkins et al. (2010) found no differences in abstinence outcomes during a short-term 5-day quit attempt. Again, this may be due in part to differences in abstinence-contingent payment conditions (half the participants in Perkins et al.

[2010] study did not receive abstinence-contingent payments and the remainder received $12 per day for meeting abstinence criteria) and/or the expected abstinence durations. These differences in magnitude and sensitivity suggest that the longer abstinence duration and/or the decelerating payment schedule used in the present study may be beneficial for magnifying varenicline��s effects on latency to relapse in short-term models of cessation. Smoking Reward The present study found that varenicline significantly reduced scores on subjective report items reflecting positive (liked, stimulated, and buzzed) and negative (dizzy and nauseous) effects of smoking during a period of abstinence and also seemed to attenuate ratings of some sensory aspects of smoking (smell, chest and throat sensations) that could operate as secondary or conditioned reinforcers associated with smoking.

These findings replicate and extend previous reports of varenicline-induced reductions in subjective measures of smoking reward (e.g., cigarette liking and satisfaction) obtained both in clinical trials (Gonzales et al., 2006; Cilengitide Jorenby et al., 2006; Oncken et al., 2006) and laboratory studies (Patterson et al., 2009; Perkins et al., 2010).