There are various definitions of what constitutes a drug. These definitions have changed over time. For our purposes, a drug is often described as any substance, solid, liquid or gas that changes the functions or structures of the body. This excludes food and water, which are required to maintain normal body functioning.
The drugs of most concern to the community are those that affect a personís central nervous system. These are the psychoactive drugs. They act on the brain and can change the way a person thinks, feels or behaves.