Crack is sold in small, inexpensive doses that are smoked. Its effects are felt immediately and are very intense and short-lived.

The intensity of the psychological effects of cocaine depends on the dose and rate of entry to the brain. Cocaine reaches the brain through the snorting method in three to five minutes. Intravenous injection of cocaine produces a rush in 15-30 seconds, and smoking produces an almost immediate intense experience. These intense effects can be followed by a "crash."

Effects

Increased alertness, excitation, euphoria (sometimes followed by a dysphoric "crash"), increased pulse rate and blood pressure, insomnia and loss of appetite.

Overdose Effects

Agitation, increased body temperature, hallucinations, convulsions, possible death.

(Excerpts from justthinktwice.com)