Drugs whose manufacture, importation, possession, use and distribution are regulated by the government are considered controlled substances, states Drugs.com. As of 2015, controlled substances are classified into five schedules: Schedule 1, Schedule 2, Schedule 3, Schedule 4 and Schedule 5. The classification of drugs into each schedule is dependent on whether they are currently acceptable for medical treatment in the United States, their potential for abuse and the probability of dependence when abused, according to the Drug Enforcement Administration.
Schedule 1 drugs have a high likelihood for abuse and are unacceptable for medical use in the United States. Examples of drugs classified as schedule 1 include peyote, marijuana, heroin, methaqualone and LSD, as listed by the Drug Enforcement Administration.
Schedule 2 drugs have a high possibility for abuse, but they are acceptable for use in medical treatment under strict limits, according to Drugs.com, and drugs under this category can lead to acute physical or psychological dependence. Examples of Schedule 2 drugs include methadone, oxycodone, hydrocodone, amphetamine and glutethimide, as noted by the Drug Enforcement Administration.
Schedule 3 drugs have a lower potential for abuse in comparison to Schedule 1 and Schedule 2 drugs. Their abuse can lead to a high psychological dependence and a low or moderate physical dependence, according to Drugs.com. Examples of Schedule 3 drugs include methyltestosterone, buprenorphine, phendimetrazine and nandrolone. Schedule 4 and Schedule 5 drugs are accepted for medical treatment in the United States, and they have a much lower likelihood for abuse and can cause limited psychological and physical dependence.