Pharmacologic determinants of tobacco dependence

Nicotine is one of the most widely abused psychoactive drugs and far more people trying it progress to regular use than those trying heroin, cocaine, or alcohol. Since the early 20th century, it has been understood that tobacco use is driven largely by nicotine's pharmacological actions. Nicotine produces reinforcing effects, tolerance and physical dependence, and pharmacological effects that smokers enjoy, such as modulation of mood, appetite, and task performance. Pharmacokinetic properties of tobacco-based nicotine products optimize abuse potential. Cigarette smoke inhalation delivers high nicotine concentrations to the brain and other organs within 10 s of inhalation. Nicotine's acute effects dissipate in a few minutes, encouraging the smoker to smoke frequently throughout the day to maintain its pleasurable effects and prevent withdrawal symptoms. Nicotine and other constituents of smoke also provide sensory stimuli which, through repeated pairings, become conditioned reinforcers and further strengthen tobacco self- administration, creating an extremely persistant behavior. Nicotine replacement medications provide relief of cigarette withdrawal symptoms and are effective aids in smoking cessation; however, sustaining long-term abstinence can still be very difficult.