Pharmacologic approaches to smoking cessation.

Only 25 years ago, tobacco dependence was believed to be a simple overuse problem. Research in the last 5 years has demonstrated a much more complex and profound neurochemical and behavioral disorder. Nicotine receptors in the locus coeruleus and the midbrain mesolimbic dopaminergic system activate both arousal state and enhance cognitive functioning (locus coeruleus) and activate the brain's "pleasure center" (mesolimbic system). Pharmacologic treatments, which must be completely integrated into the behavioral treatment plan, alter these profound central nervous system nicotine effects. Currently the only agent with clear scientific evidence for treatment efficacy is nicotine itself. Available only in a transmucosally delivered ion-exchange resin as nicotine polacrilex (Nicorette), nicotine should soon be available in other delivery forms that will have different absorption kinetics: transdermal patch, nasal spray, and vapor inhaler. Other agents in various phases of preclinical and clinical evaluation include 5-HT1A partial agonists such as buspirone; alpha 2-noradrenergic agonists such as clonidine; tricyclics such as doxepin; serotonin re-uptake antagonists such as fluoxetine; ACTH; 5-HT2 antagonists such as ritanserin; central excitatory amino acid inhibitors such as kynurenate; and calcium channel blockers.