Definitions and Information A drug is a substance which, when introduced to the body, changes actions or reactions in body functions or structures. Drugs may be taken medically to alter states of the body or assist the body in fighting disease. Drugs rarely impact on only one part of the body or one body function. Aspirin, as an example, is a pain reliever. Aspirin also impacts on the body by thinning the blood.
Drugs travel through the entire body, and impact on several parts of the body.
A drug abuser is not concerned with the impact the drug may have on the blood system, the immune system, or in its ability to relieve pain. The drug abuser is focused solely on the changes the substance creates to the brain. A depressant drug is one which depresses the central nervous system. A depressant drug will cause the activity in the brain to slow down. The rate of breathing, as well as the heart rate, will also slow down.