Drug diversion
In the terminology of the Drug Enforcement Administration, diversion is the use of prescription drugs for recreational purposes. The term comes from the "diverting" of the drugs from their original purposes.
note: Drug Diversion may also refer to programs available to first time drug law infractors which "divert" them from the criminal system to a program of education and rehabilitation.

# Drugs that are diverted, in an approximate order of popularity
- Opioids (opium analogues) such as hydrocodone and OxyContin. These have similar effects to opium and heroin.
- Pseudoephedrine-containing drugs sold over the counter are used as an ingredient to make methamphetamine.
- DXM, the active ingredient of Robitussin, is abused for its effects which are similar to Ketamine and PCP.
- Depressants such as Valium.
- Antidepressants, which may be stimulants, Tricyclics, SSRIs or other medications and may be snorted by abusers.
The DEA has implemented various measures against drug diversion in the United States. For example, retail sales of pseudoephedrine are limited in certain stores to specified amounts.  In addition, several States have enacted legislation requiring retail sales of pseudoephedrine products to be recorded, with proof of identification required.
Some critics feel that the importance of drug diversion is glossed over in the media and popular discussion. For example, in the recent Florida case of Rush Limbaugh being accused of abusing pain-killers, some argued that the similarity between the pain killers and heroin was not made clear. The higher dose pills of prescription pain killers are often stronger than the street rock heroin sold in most cities, and are preferred or at least used indiscriminately by opiate drug abusers.  It is also important to remember that while street drug purity can vary widely, including the environmental conditions under which street drugs are produced, pharmaceutical-grade controlled substances are produced under government supervision using the best manufacturing technology available.
In another recent Florida case, Richard Paey, also in chronic pain after botched back surgery, was sent to prison for 25 years after the DEA told Paey's New Jersey doctor that Paey was selling his pills. Then the doctor abandoned him and Paey committed prescription fraud to get relief, primarily from Percocet. Technically the Percocet was "diverted" since Paey obtained it illegally. Paey never sold any of it or attempted to use any of the so-called "street drugs". The Paey case has been widely reported as an example of how well-intentioned law can have devastating effects on patients of modest means.
Some critics go so far as to contend that drug diversion has been purposely allowed to happen, primarily by opioid manufacturers who profit off of the addiction of their customers. They also point to new products such as "dex-alone" which is a pill marketed specifically that it contains pure DXM without other compounds which would have an adverse effect at the levels of abuse.

# Registration of drug suppliers and dispensers
21 U.S.C.  823 of the Controlled Substances Act provides for registration of manufacturers and distributors of controlled substances. The criteria for registering manufacturers of Schedule I and II drugs are particularly strict and call for "limiting the importation and bulk manufacture of such controlled substances to a number of establishments which can produce an adequate and uninterrupted supply of these substances under adequately competitive conditions for legitimate medical, scientific, research, and industrial purposes." The Attorney General must make a positive determination that the registration would be "consistent with the public interest."
For manufacturers of other drugs, and for drug distributors, the regulations are substantially less strict: "The Attorney General shall register an applicant... unless he determines that the issuance of such registration is inconsistent with the public interest." The criteria for both manufacture and distribution is somewhat biased in favor of established industries, favoring "past experience" and a record of compliance with drug laws.
The Controlled Substances Act also provides for the registration of medical practitioners (i.e., physicians, dentists, veterinarians, etc.), pharmacies and hospitals that prescribe, administer, or dispense controlled substances directly to patients, as well as individuals conducting approved research involving controlled substances.  This category also includes narcotic treatment programs that administer and dispense primarily Methadone for narcotic addiction treatment.