A controlled substance is a drug or chemical whose manufacture, distribution, possession, and use are regulated by law. These substances are classified into schedules based on their potential for abuse, medical use, and safety. For example, substances like heroin and cocaine are considered highly addictive and are placed in the stricter schedules. The regulation of controlled substances is intended to prevent misuse and protect public health. Agencies like the Drug Enforcement Administration (DEA) in the United States oversee these regulations, ensuring that medications such as opioids and benzodiazepines are prescribed and dispensed safely.