The U.S. Drug Enforcement Administration classifies controlled substances as substances that have a potential for abuse or dependence, such as heroin, methamphetamine and cocaine. The DEA categorizes controlled substances by schedules, with Schedule I controlled substances being those with no current accepted medical use in the United States and the highest abuse potential and Schedule V controlled substances having the least potential for abuse or dependence.
Schedule I narcotics include drugs such as peyote, heroin, Ecstasy and methaqualone. The federal government does not sanction doctors to prescribe these substances, and they have a high potential for causing dependence and abuse in users.
Schedule II/IIN controlled substances include narcotics such as methadone, oxycodone, hydromorphone and hydrocodone. It also includes stimulants such as amphetamines, methylphenidate and methamphetamine. Pentobarbital, glutethimide and amobarbital are other Schedule II/IIN substances. Substances in this schedule have a high potential for severe physical or psychological dependence and abuse.
Schedule III/IIIN substances pose a lower potential for abuse and dependence. These drugs include narcotics containing no more than 90 milligrams of codeine per dose. Also included are buprenorphine, phendimetrazine and anabolic steroids.
Schedule IV controlled substances have a low abuse potential. These drugs include alprazolam, clonazepam, lorazepam and triazolam, among others.
Schedule V controlled substances have an even lower potential for abuse. These substances include cough medicines containing codeine.