Do smokers self-administer pure nicotine? A review of the evidence

Rationale. Nicotine is almost universally believed to be the primary agent motivating tobacco smoking and the main impediment to cessation. A principal argument in support of the presumed reinforcing properties of nicotine is that smokers self-administer pure nicotine. However, the evidence for nicotine self-administration in smokers has not been critically examined. Objectives. To review and examine the empirical basis for the assertion that smokers self-administer pure nicotine. Methods. We reviewed all the studies we were able to locate that are cited as demonstrating self-administration of nicotine, isolated from tobacco, in normal smokers and non-smokers. These studies investigated self-administration of intravenous nicotine, nicotine gum and nicotine spray. Using the authors' own criteria, we examined whether these studies in fact demonstrate nicotine-self administration. Results. None of the studies we reviewed demonstrated nicotine self-administration in smokers. Both smokers and non-smokers failed to show preference for nicotine over placebo in any of these studies, including in a series of six reports of overnight abstinent smokers having access to nicotine nasal spray, a rapidly absorbed form of nicotine. Conclusions. The common statement that smokers self-administer pure nicotine lacks empirical support. Smokers in fact do not administer pure nicotine in any of the forms studied to date, even when abstinent and presumably nicotine-deprived. This conclusion necessitates a critical re-examination of the nicotine addiction thesis.