Illegal drugs are those that are not prescribed by a doctor or bought at a drugstore. They are sometimes also called "street drugs."
Some examples of illegal drugs include heroin (a narcotic); cocaine (a stimulant); LSD, mescaline, PCP, methamphetamine, and psilocybin (hallucinogens); marijuana and hashish (cannabis); and gamma-hydroxybutyrate (GHB). Although GHB is legal in Europe for anesthetic uses and in the United States for government-approved clinical trials for treating narcolepsy, it has been otherwise illegal in the United States since 1990.
The effects of illegal drugs can be unpredictable because: