How does tobacco addiction work?
Nicotine links to central receptors-cholinergic, adrenergic, dopaminergic and serotonergic-to produce the effects noted above (7). The mode of delivery (whether smoking or nicotine gum or patch) determines peak blood nicotine level and time to peak level. Inhaling tobacco smoke delivers to the brain the highest and sharpest peaks of nicotine and thereby maximizes its psychoactive effects. Nicotine has a half-life averaging two hours. Smokers usually begin their day with low nicotine levels that rise sharply in the morning, plateau in the afternoon when smoking slows, and fall during sleep. Each smoker has a characteristic, 24-hour blood nicotine curve and maintains blood nicotine levels within a specific range for each hour of the day. When blood nicotine falls beneath the smoker s zone of comfort, withdrawal symptoms may begin: anxiety, restlessness, inability to concentrate, irritability, severe urges to smoke, reduced pulse rate, headaches, and problems with sleeping. If blood nicot
