The Controlled Substances Act (CSA) is a United States federal law.  It controls what drugs American people and companies can have, make, import, and use.  It also controls what drugs doctors can prescribe.

"Controlled substances" include illegal drugs, chemicals that are used to make illegal drugs, and some medications.  If a government has rules or laws about a certain drug, then that drug is called a controlled substance.

The United States Congress passed the law as part of the Comprehensive Drug Abuse Prevention and Control Act of 1970.  President Richard Nixon signed the bill into law on October 27, 1970.

Summary
The Controlled Substances Act (CSA) sets laws about:
 Which drugs are controlled substances
 When it is illegal to make, sell, or have controlled substances
 What kinds of importation and exportation of controlled substances is illegal
 The punishments for breaking these laws

The CSA does not include alcohol or tobacco as "controlled substances."

Schedules
The CSA divides controlled substances up into five groups, called Schedules.  Drugs are put into these categories based mostly on:
 How easily and commonly they are abused;
 Whether they have any accepted medical uses;
 International treaties
 For example, the United Nations may make a treaty to control a new drug.  If the United States agrees to that treaty, then the CSA has to be amended (changed) to add that drug to one of the Schedules

Amendments

Since the CSA was created in 1970, many new illegal drugs and medications have been developed.  Because of this, the Act has been amended many times to add on new types of drugs.

For example, since 1970, the CSA has been amended:
 In 1978, to include barbiturates, benzodiazepines, psychedelic drugs like LSD, and amphetamine-type stimulants
 In 1986, to add designer drugs like MDMA (Ecstasy)
 In 1988, to include chemicals and machines that were being used to make cocaine
 In 1990, to add anabolic steroids (man-made steroids that act like testosterone in the body)
 In 1993, to try to control methamphetamine trafficking
 In 2008, to prevent people from getting drugs from online pharmacies without having prescriptions

The Schedules

There are five different Schedules of controlled substances, numbered IV (one through five in Roman numerals).  The CSA describes the different Schedules based on three things:
 Potential for abuse: How likely is this drug to be abused?
 Accepted medical use: Is this drug used as a treatment in the United States?
 Safety and potential for addiction: Is this drug safe?  How likely is this drug to cause addiction?  What kinds of addiction?

This table gives a summary of the differences between the different Schedules.

Schedule I

The CSA says that no doctor in the United States can write a prescription for a Schedule I drug.  Some states have passed laws allowing doctors to prescribe marijuana for diseases like cancer and AIDS.  Even though those prescriptions are legal in those states, they are still illegal under the CSA.

Here are some examples of Schedule I drugs:
 GHB
 Heroin
 LSD
 Marijuana
 Synthetic cannabis
 MDMA ("Ecstasy")
 Mescaline
 Peyote
 Psilocybin

Schedule II

Schedule II drugs are the most-controlled type of drugs that a doctor can write a prescription for.  Some drugs that are usually illegal are on Schedule II.  They are on Schedule II instead of Schedule I because sometimes, they can be used for medical reasons.  For example, Schedule II includes cocaine, because it can stop bleeding and kill pain in the mouth, throat, and nose.  Schedule II also includes methamphetamine, because it is sometimes used to treat Attention-Deficit Hyperactivity Disorder (ADHD) and severe obesity.

Other drugs on Schedule II include:
 Amphetamine, Adderall, and other medications used to treat ADHD
 Methylphenidate (also called Ritalin or Concerta): Used to treat ADHD
 Opiate painkillers: fentanyl, oxycodone, morphine, hydromorphone, hydrocodone, and pure codeine
 Methadone, which is used to treat severe pain or opiate addiction
 Phencyclidine (PCP), which used to be used as an anesthetic for people and animals
 Short-acting barbiturates, like pentobarbital (a sedative and strong anti-seizure medication)

The CSA puts limits on prescriptions for Schedule II drugs.  For example, prescriptions for these drugs cannot be refilled.  The patient cannot get more of the medication at the pharmacy without getting a new prescription.  Also, the doctor must write the prescription  they cannot call or fax the prescription to the pharmacy.  The pharmacy needs an original copy of the prescription.

Schedule III

Schedule III drugs are less controlled than Schedule II drugs.  Doctors can send these prescriptions to a pharmacy by fax or phone.  These prescriptions can be refilled five times in six months without the patient needing a new prescription.

Drugs in Schedule III include:
 Anabolic steroids: Used to treat many medical problems, like growth failure (when a child does not grow normally)
 Buprenorphine (also called Suboxone or Subutex): Used to treat opiate addiction
 Ketamine: Used as an anesthetic
 Marinol: Man-made tetrahydrocannabinol (THC, a chemical in marijuana): Used to treat nausea and vomiting from chemotherapy, and loss of appetite from AIDS

Schedule IV
Schedule IV drugs have the same rules for prescriptions and refills that Schedule III drugs do.  Examples of Schedule IV drugs include:
 Benzodiazepines, like clonazepam (Klonopin), diazepam (Valium), and lorazepam (Ativan): Used to treat anxiety
 Benzodiazepine-like drugs used for insomnia, like zolpidem (Ambien)
 Long-acting barbiturates like phenobarbital: Used to control seizures

Schedule V

Schedule V drugs are the least strictly controlled of all the controlled substances.  A doctor can call or fax the prescription to the pharmacy.  There is no limit on the number of times a prescription can be refilled.

Examples of Schedule V drugs include:
 Cough medicines with small amounts of codeine in them
 Mixtures with a small amount of opium in them (used to treat diarrhea)
 Some anti-seizure medications, like pregabalin (Lyrica)

Enforcement
The United States Drug Enforcement Administration (DEA) is in charge of enforcing the CSA.  The DEA is part of the United States Department of Justice.

Usually, only two government agencies can add or remove drugs from a Schedule.  These agencies are the (DEA) and the United States Food and Drug Administration (FDA).  However, sometimes Congress passes special laws to add a drug to the CSA.

Anyone can ask the DEA to add a drug, remove a drug, or change a drug to a different Schedule in the CSA.  Even a regular person can petition the DEA for a change.  After it gets a petition, the DEA starts an investigation of the drug.

During these investigations, the DEA gathers a lot of information, talks to different government agencies, gets the FDA's opinion, and does research.  Because all of this takes time, a federal law allows the Attorney General of the United States to put a drug on Schedule I for a year.  The law only allows this when there is "an imminent hazard" (an immediate threat) "to the public safety."  For example, in 2011, the Attorney General used this law to put synthetic cannabinoids on Schedule I.

Notes

References

1970 in the United States
Drugs
United States federal legislation
1970s in law