Pharmacokinetic-pharmacodynamic modeling of the effect of varenicline on nicotine craving in adult smokers.

introductionVarenicline has been shown to significantly reduce craving and several aspects of smoking reinforcement in clinical trials, compared with placebo. This is the first report describing the concentration-effect relationship of varenicline on relief of craving.

methodsThe pharmacokinetics (PK) and pharmacodynamics (PD) of a single 2mg dose of varenicline were investigated in 40 smokers in a randomized, crossover study comparing the effect of varenicline with placebo on ameliorating abstinence-and cue-induced craving and withdrawal symptoms. Subjects were asked to complete self-reported questionnaires (Smoking Urges Scale and Minnesota Nicotine Withdrawal Scale [MNWS]) and blood samples were simultaneously collected for measurement of varenicline concentrations. Only the data from the 4-hr postdose abstinence period (just prior to the cue session) were analyzed. Data were described by a 2-compartment PK model and a linear PD model with first-order onset/offset rate constants describing the placebo response "kinetics." Response was described as the net effect of the baseline, placebo, and drug responses.

resultsVarenicline significantly decreased mean craving score when compared with placebo and the magnitude of this response was related to varenicline concentration. The time-course and magnitude of both placebo and varenicline craving response were characterized by a large degree of unexplained variability. Simulations were used to illustrate the expected craving response over time and its associated random variability after chronic dosing.

conclusionsCraving reduction is associated with increased varenicline concentrations. The relatively rapid onset of this effect within 4 hr postdose suggests that, smokers may experience some craving relief after acute administration of varenicline.