There are more than 4,000 chemicals found in the smoke of tobacco products. The cigarette is a very efficient and highly engineered drug delivery system. By inhaling tobacco smoke, the average smoker takes in 1–2 milligrams of nicotine (the chemical that causes addiction) per cigarette. Thus, a person who smokes about 1½ packs (30 cigarettes) daily takes at least 300 mg "hits" of nicotine to the brain each day. Immediately after exposure to nicotine, there is a "kick" caused in part by the drug’s stimulation of the adrenal glands and the resulting discharge of epinephrine (adrenaline). The rush of adrenaline stimulates the body and causes an increase in blood pressure, respiration, and heart rate.

Smokers have access to numerous media and educational messages, which state that tobacco products are unhealthy. Many nicotine-addicted patients want to quit or have attempted to quit. Why is it so hard to quit a habit a person knows may kill them? As with many addictive drugs, it is believed that nicotine affects the release of dopamine into the brain. Dopamine fuels sensations of pleasure and relaxation. Over time, nicotine becomes something a person’s body needs. In other words, after using nicotine for an extended period, the body becomes addicted to the substance. Both mind and body feel a need for the drug and its continued use. Cigarette smoking produces a rapid distribution of nicotine to the brain, peaking within 10 seconds of inhalation. However, the acute effects dissipate quickly, as does the feeling of euphoria, which causes the smoker to continue dosing to maintain the drug’s pleasurable effects and prevent withdrawal.

Nicotine withdrawal symptoms include irritability, craving, depression, anxiety, cognitive and attention deficit, sleep disturbances, and increased appetite. These symptoms may begin within a few hours after the last cigarette, quickly driving people back to tobacco use. Symptoms peak within the first few days of smoking cessation and usually subside within a few weeks. For some people, however, symptoms may persist for months. Of the 35 million smokers who desire to quit smoking each year, more than 85% of those who attempt cessation relapse, most within 1 week.

Withdrawal is difficult due to the many physical and behavioral effects related to smoking. Symptoms of withdrawal can be severe. For some smokers, the feel, smell, and sight of a cigarette and the ritual of obtaining, handling, lighting, and smoking the cigarette are all associated with the pleasurable effects of smoking and can make cravings worse. Nicotine replacement therapies such as gum, patches, and inhalers may help alleviate the pharmacological aspects of withdrawal, however, cravings often persist. Behavioral therapies can help smokers identify environmental triggers of craving so they can employ strategies to prevent or circumvent these symptoms and urges.32