Cigarette smoking produces a rapid distribution of nicotine through the bloodstream and nicotine crosses the blood–brain barrier, with drug levels peaking in the brain within 10 s of inhalation (Le Houezec 2003). Smoking produces high concentrations of nicotine in the brain that are comparable to concentrations observed after intravenous administration (Hukkanen et al. 2005). Various studies have shown that smokers will try to maintain their plasma nicotine concentration within a narrow range by modulating their smoking behavior. This may include altering the number of cigarettes they smoke per day or how they smoke a cigarette (e.g., depth of inhalation) (Benowitz 2008).
