A drug is any substance, natural or synthetic, that is used to alter the workings of the body. They are most commonly used in the diagnosis and treatment of disease and its symptoms. This use of drugs is more commonly referred to as medicine. Drugs and their effects are also used recreationally to achieve pleasure and altered bodily states. This use of drugs is often illegal and is referred to as narcotics.

All drugs, whether medicine or narcotic, carry the risk of addiction or dependence. Dependence can be physical or psychological and once established will be very difficult to break out of. This is where drug treatment is used. The treatment aims at assisting the dependent user to break the addiction and get safely through the side effects associated with quitting the drug. These side effects can include nausea, headache and vomiting.

As drug addiction becomes ever more prevalent, drug treatment is growing in importance.