A drug is a chemical substance that can change how your body and mind work. Drugs that can be dangerous are ones that people use to get high and change the way they feel. They can be drugs like marijuana, cocaine, or heroin. Or they may be drugs legally sold to adults everywhere, like alcohol and tobacco.
Medicines can also be misused when people take them to get high instead of the way their doctor advises. People can even misuse cough or cold medicines from the store if they ignore the directions and take too much at one time.
People use drugs for many reasons:
Source: National Institute of Health