Psychoactive substances are regulated in the United States in a system of schedules. There are five schedules with Schedule I the most rigorously controlled and Schedule V the least controlled. Schedule I drugs may not be prescribed while schedules II - V may be prescribed by a physician with varying amounts of paperwork and reporting requirements.

Schedule I - [Full Text and Listing]

Examples : LSD, MDMA, Marihuana, DMT, Peyote, Psilocybin, Mescaline, Heroin


• The drug or other substance has a high potential for abuse.
• The drug or other substance has no currently accepted medical use in treatment in the United States.
• There is a lack of accepted safety for use of the drug or other substance under medical supervision.
  
  Schedule I drugs may not be prescribed.
  
  

Schedule II - [Full Text and Listing]

Examples : Cocaine, Hydrocodone, Morphine, Opium, Amphetamine, PCP


• The drug or other substance has a high potential for abuse.
• The drug or other substance has a currently accepted medical use in treatment in the United States or a currently accepted medical use with severe restrictions.
• Abuse of the drug or other substance may lead to severe psychological or physical dependence.
  
  Schedule II drugs may be prescribed with a written prescription from a licensed physician or nurse practitioner.
  
  

Schedule III - [Full Text and Listing]

Examples : Anabolic Steroids, Marinol (Synthetic THC), Ketamine, LSA


• The drug or other substance has a potential for abuse less than the drugs or other substances in Schedules I and II.
• The drug or other substance has a currently accepted medical use in treatment in the United States.
• Abuse of the drug or other substance may lead to moderte or low physical dependence or high psychological dependence.
  
  Schedule III drugs may be prescribed by a licensed physician or nurse practitioner. Prescriptions may be refilled using phoned-in prescriptions.
  
  

Schedule IV - [Full Text and Listing]

Examples : Valium, Xanax, Librium, Rohypnol, Klonopin


• The drug or other substance has a low potential for abuse relative to the drugs or other substances in Schedule III.
• The drug or other substance has a currently accepted medical use in treatment in the United States.
• Abuse of the drug or other substance may lead to limited physical dependence or psychological dependence relative to the drugs or other substances in Schedule III.
  
  Schedule IV drugs may be prescribed by a licensed physician or nurse practitioner. Prescriptions may be refilled using phoned-in prescriptions.
  
  

Schedule V - [Full Text and Listing]

Examples : Buprenorphine, Pyrovalerone, Prescription Meds containing low quanitites of Codeine, Opium, etc.


• The drug or other substance has a low potential for abuse relative to the drugs or other substances in Schedule IV.
• The drug or other substance has a currently accepted medical use in treatment in the United States.
• Abuse of the drug or other substance may lead to limited physical dependence or psychological dependence relative to the drugs or other substances in Schedule IV.
  
  Schedule V drugs may be prescribed by a licensed physician or nurse practitioner. Prescriptions may be refilled using phoned-in prescriptions. There are some drugs and preparations in Schedule V that are exempted from prescription requirements. Although not specifically allowed by the federal government, some states allow certain Schedule V drug preparations to be sold without prescriptions by pharmacists.
  
  

The complete CSA can be found here.