You may have been prescribed a pain, anxiety, insomnia or stimulant medication that is monitored by the Drug Enforcement Administration (DEA). These medications are called ‘controlled substances’ as they require your Doctor to have a specific prescription license to write for these. The reason why the have to have this special certificate is these medications have potential for causing problems with abuse, dependence and addiction. Definitions: Drug abuse is the deliberate use of a medication beyond a Doctor’s prescription. Drug dependence occurs when the body develops tolerance to the drug meaning higher doses are needed for the same effect. Drug addiction occurs when a person has drug dependence but also.