Nicotine is the drug that causes addiction. Pharmacologic and behavioral characteristics that determine tobacco addiction are similar to those that determine addiction to drugs such as heroin and cocaine. When a person smokes a cigarette, the body responds immediately to the chemical nicotine in the smoke. Nicotine causes a short-term increase in blood pressure, heart rate, and the flow of blood from the heart. It also causes the arteries to narrow.
Carbon monoxide reduces the amount of oxygen the blood can carry.
This, combined with the effects produced by nicotine, creates an imbalance in the demand for oxygen by the cells and the amount of oxygen the blood can supply. Smoking further increases the amount of fatty acids, glucose and various hormones in the blood. There are several ways that cigarette smoking may increase the risk of developing hardening of the arteries and heart attacks. First, carbon monoxide may damage the inner walls of the arteries, encouraging the buildup of fat in them. Over time, this causes the vessels to narrow and harden.