Schedule I drugs are those with a high potential for abuse, with an absence of any medical use, that are dangerous to the user even under medical supervision. The more commonly recognized types of these drugs are: heroin, LSD, mescaline, marijuana, and peyote.
Schedule II drugs have a high potential for abuse and a high potential for severe psychological or physical dependency, but are currently accepted for medical use. Schedule II drugs include opium, cocaine, methadone, amphetamines, and methamphetamines.
Schedule III drugs, by comparison have less potential for abuse than Schedule II drugs, a potential for moderate psychological or physical dependency, and an accepted medical use. The most well known Schedule III drug is naline, which is used to detect narcotic use.
Schedule IV drugs have less potential for abuse than Schedule III drugs, they have a limited potential for dependency, and they are accepted in medical treatment. These drugs include tranquilizers, meprobamate, chloral hydrate, most drugs that cause sleep, and sedatives.