Cocaine is a strong central nervous system stimulant. Physical effects of cocaine use, including crack, include constricted blood vessels and increased temperature, heart rate, and blood pressure. Users may also experience feelings of restlessness, irritability, and anxiety.

Smoking crack delivers large quantities of the drug to the lungs, producing effects comparable to intravenous injection. These effects are felt almost immediately after smoking, are very intense, but do not last long. For example, the high from smoking cocaine may last from 5 to 10 minutes, while the high from snorting the drug can last for 15 to 20 minutes.

Evidence suggests that users who smoke or inject cocaine may be at even greater risk of causing harm to themselves than those who snort the substance. Cocaine smokers may suffer from acute respiratory problems including coughing, shortness of breath, and severe chest pains with lung trauma and bleeding. Smoking crack cocaine can also cause particularly aggressive paranoid behavior in users.

An added danger of cocaine use is when cocaine and alcohol are consumed at the same time. When these substances are mixed, the human liver combines cocaine and alcohol and manufactures a third substance, cocaethylene. This intensifies cocaine's euphoric effects, while also possibly increasing the risk of sudden death. Most cocaine-related deaths are a result of cardiac arrest or seizures followed by respiratory arrest.

Cocaine is a powerfully addictive drug. Compulsive cocaine use seems to develop more rapidly when the substance is smoked rather than snorted. A tolerance to the cocaine high may be developed and many addicts report that they fail to achieve as much pleasure as they did from their first cocaine exposure.