Cocaine

Cocaine is a naturally derived CNS (central nervous system) stimulant extracted and refined from the Coca plant grown primarily in the Andean region of South America. Cocaine is typically a white-ish powder with a bitter, numbing taste. It is most often insufflated (snorted), though it can also be injected and used orally.

While powder cocaine can be smoked to some effect (despite common belief otherwise), it is a very inefficient method of ingestion. Because of the high temperatures present when smoking, powder cocaine tends to burn rather than vaporizing. For this reason, freebase cocaine, also known as crack in its street form, is created from powder cocaine for smoking. Freebase cocaine vaporizes at smoking temperatures providing more effect with less material, as well as faster onset and a more intense high than powder cocaine.

As with many substances, the effects of cocaine depend greatly on the person and the dose. Possible effects include feelings of well-being, decreased appetite, stimulation, sexual arousal, and increased focus. Negative effects can include increased body temperature and heart rate, agitation and anxiety, paranoia, dizziness, nausea/vomiting, violent behavior, kidney failure, seizure, stroke, and heart attack.

Street cocaine is quite often impure. The more direct the route of administration, the more dangerous this can be. Injecting impure cocaine can be deadly. Repeated snorting can cause severe damage to the nose. Smoking of freebase cocaine can cause breathing difficulties.

http://www.erowid.org/chemicals/cocaine/cocaine_basics.shtml