Cocaine can become an addiction very quickly and is a very difficult habit to break. Studies have shown that animals will work very hard after a single injection of cocaine.  They will also choose cocaine over water and food and will choose cocaine even when their behavior is punished. It was proven that animals must have their access to cocaine limited in order not to take lethal doses. Studies have also show that people addicted to cocaine behaved in a similar manner. One of the signs of cocaine use is the addicts will go to great lengths to get cocaine and continue to take it even when school, job performance or relationships begin to suffer.

There are many different ways of administering cocaine such as sniffing or snorting, injecting and smoking, including free-basing and crack cocaine. Snorting is the process of inhaling cocaine powder through the nose where it is absorbed into the bloodstream through the nasal tissues. Injecting is the act of using a needle to release the drug directly into the bloodstream. Smoking involves inhaling cocaine vapor or smoke into the lungs where absorption into the bloodstream is as rapid as by injection.

"Crack" or "crack cocaine" is the street name given to cocaine that has been processed from cocaine hydrochloride to a free base for smoking.

Rather than requiring the more volatile method of processing cocaine-using ether, crack cocaine is processed with ammonia or sodium bicarbonate (baking soda) and water and heated to remove the hydrochloride, thus producing a form of cocaine that can be smoked. The term "crack" refers to the crackling sound heard when the mixture is smoked (heated), presumably from the sodium bicarbonate.

Cocaine is a strong central nervous system stimulant that interferes with the reabsorption process of dopamine, a chemical messenger associated with pleasure and movement. Dopamine is released as part of the brain's reward system and is involved in the high that characterizes cocaine consumption.

Signs of Cocaine use include constricted peripheral blood vessels, dilated pupils, increased temperature, heart rate and blood pressure, hyper-alertness, lack of fatigue/sleeplessness, panic, extremely talkative; fast speech, runny nose or bloody nose, seizures from high doses or bad reaction, white powder seen on face or clothes, small spoon-like items used for snorting, mirrors and razor blades used for making lines, rolled money bills used for snorting, small bottles with screw on lids for storing and possession of small plastic packets with white residue.

The duration of cocaine's immediate euphoric effects, which include hyper-stimulation, reduced fatigue, and mental clarity, depends on the route of administration. The faster the absorption, the more intense the high. On the other hand, the faster the absorption, the shorter the duration of action. The high from snorting may last 15 to 30 minutes, while that from smoking may last 5 to 10 minutes. Increased use can reduce the period of stimulation.

Some other signs of Cocaine use are feelings of restlessness, irritability, and anxiety. An appreciable tolerance to the high may be developed, and many addicts report that they seek but fail to achieve as much pleasure as they did from their first exposure. Scientific evidence suggests that the powerful neuropsychological reinforcing property of cocaine is responsible for an individual's continued use, despite harmful physical and social consequences. In rare instances, sudden death can occur on the first use of cocaine or unexpectedly thereafter. However, there is no way to determine who is prone to sudden death.