A package of recreational drugs disguised in "bath salts" packaging.
A designer drug is a structural or functional analog of a controlled substance
 that has been designed to mimic the pharmacological effects of the 
original drug, while avoiding classification as illegal and/or detection
 in standard drug tests. Designer drugs include psychoactive substances that have been designated by the European Union as new psychoactive substances (NPS) as well as analogs of performance-enhancing drugs such as designer steroids.
 Some of these were originally synthesized by academic or industrial 
researchers in an effort to discover more potent derivatives with fewer 
side effects and were later co-opted for recreational use. Other 
designer drugs were prepared for the first time in clandestine laboratories.
 Because the efficacy and safety of these substances have not been 
thoroughly evaluated in animal and human trials, the use of some of 
these drugs may result in unexpected side effects.
The development of designer drugs may be considered a subfield of drug design. The exploration of modifications to known active drugs—such as their structural analogues, stereoisomers, and derivatives—yields drugs that may differ significantly in effects from their "parent" drug (e.g., showing increased potency, or decreased side effects).
 In some instances, designer drugs have similar effects to other known 
drugs, but have completely dissimilar chemical structures (e.g. JWH-018 vs THC).
 Despite being a very broad term, applicable to almost every synthetic 
drug, it is often used to connote synthetic recreational drugs, 
sometimes even those which have not been designed at all (e.g. LSD, the 
psychedelic side effects of which were discovered unintentionally). 
In some jurisdictions, drugs that are highly similar in structure
 to a prohibited drug are illegal to trade regardless of that drug's 
legal status. In other jurisdictions, their trade is a legal grey area, 
making them grey market
 goods. Some jurisdictions may have analogue laws which ban drugs 
similar in chemical structure to other prohibited drugs, while some 
designer drugs may be prohibited irrespective of the legal status of 
structurally similar drugs; in both cases, their trade may take place on
 the black market.
History
United States of America
1920s–1930s
Following the passage of the second International Opium Convention in 1925, which specifically banned morphine, the diacetyl ester of morphine, heroin, and a number of alternative esters of morphine quickly started to be manufactured and sold. The most notable of these were dibenzoylmorphine and acetylpropionylmorphine,
 which have virtually identical effects to heroin but were not covered 
by the Opium Convention. This then led the Health Committee of the League of Nations
 to pass several resolutions attempting to bring these new drugs under 
control, ultimately leading in 1930 to the first broad analogues 
provisions extending legal control to all esters of morphine, oxycodone,
 and hydromorphone. Another early example of what could loosely be termed designer drug use, was during the Prohibition era in the 1930s, when diethyl ether was sold and used as an alternative to illegal alcoholic beverages in a number of countries.
1960s–1970s
During
 the 1960s and 1970s, a number of new synthetic hallucinogens were 
introduced, with a notable example being the sale of highly potent 
tablets of DOM in San Francisco in 1967.
 There was little scope to prosecute people over drug analogues at this 
time, with new compounds instead being added to the controlled drug 
schedules one by one as they became a problem, but one significant court
 case from this period was in 1973, when Tim Scully and Nicholas Sand were prosecuted for making the acetyl amide of LSD, known as ALD-52.
 At this time ALD-52 was not a controlled drug, but they were convicted 
on the grounds that in order to make ALD-52, they would have had to be 
in possession of LSD, which was illegal. The late 1970s also saw the 
introduction of various analogues of phencyclidine (PCP) to the illicit market.
1980s–early 1990s
The modern use of the term designer drug was coined in the 1980s to refer to various synthetic opioid drugs, based mostly on the fentanyl molecule (such as α-methylfentanyl). The term gained widespread popularity when MDMA (ecstasy) experienced a popularity boom in the mid-1980s. When the term was coined in the 1980s, a wide range of narcotics were being sold as heroin on the black market. Many were based on fentanyl or meperidine. One, MPPP, was found in some cases to contain an impurity called MPTP, which caused brain damage that could result in a syndrome identical to full-blown Parkinson's disease, from only a single dose. Other problems were highly potent fentanyl analogues, which were sold as China White, that caused many accidental overdoses.
Because the government was powerless to prosecute people for 
these drugs until after they had been marketed successfully, laws were 
passed to give the DEA
 power to emergency schedule chemicals for a year, with an optional 
6-month extension, while gathering evidence to justify permanent 
scheduling, as well as the analogue laws mentioned previously. 
Emergency-scheduling power was used for the first time for MDMA.
 In this case, the DEA scheduled MDMA as a Schedule I drug and retained 
this classification after review, even though their own judge ruled that
 MDMA should be classified Schedule III on the basis of its demonstrated
 uses in medicine. The emergency scheduling power has subsequently been used for a variety of other drugs including 2C-B, AMT, and BZP. In 2004, a piperazine drug, TFMPP, became the first drug that had been emergency-scheduled to be denied permanent scheduling and revert to legal status. 
The late 1980s and early 1990s also saw the re-emergence of methamphetamine
 in the United States as a widespread public health issue, leading to 
increasing controls on precursor chemicals in an attempt to cut down on 
domestic manufacture of the drug. This led to several alternative 
stimulant drugs emerging, the most notable ones being methcathinone and 4-methylaminorex,
 but, despite attracting enough attention from authorities to provoke 
legal scheduling of these compounds, their distribution was relatively 
limited in extent and methamphetamine continued to dominate the illicit 
synthetic stimulant market overall.
Late 1990s–2004
In the late 1990s and early 2000s, there was a huge explosion in designer drugs being sold over the internet. The term and concept of "research chemicals" was coined by some marketers of designer drugs (in particular, of psychedelic drugs in the tryptamine and phenethylamine family). The idea was that, by selling the chemicals as for "scientific research" rather than human consumption, the intent clause of the U.S. analogue drug
 laws would be avoided. Nonetheless, the DEA raided multiple suppliers, 
first JLF Primary Materials, and then multiple vendors (such as RAC Research) several years later in Operation Web Tryp. This process was accelerated greatly when vendors began advertising via search engines like Google by linking their sites to searches on key words such as chemical names and terms like psychedelic or hallucinogen.
 Widespread discussion of consumptive use and the sources for the 
chemicals in public forums also drew the attention of the media and 
authorities. 
In 2004, the US Drug Enforcement Administration raided and shut 
down several Internet-based research chemical vendors in an operation 
called Web Tryp. With help from the authorities in India and 
China, two chemical manufacturers were also closed. Many other 
internet-based vendors promptly stopped doing business, even though 
their products were still legal throughout much of the world. 
Most substances that were sold as "research chemicals" in this 
period of time are hallucinogens and bear a chemical resemblance to 
drugs such as psilocybin and mescaline. As with other hallucinogens, these substances are often taken for the purposes of facilitating spiritual processes, mental reflection or recreation. Some research chemicals on the market were not psychoactive, but can be used as precursors in the synthesis of other potentially psychoactive substances, for example, 2C-H, which could be used to make 2C-B and 2C-I
 among others. Extensive surveys of structural variations have been 
conducted by pharmaceutical corporations, universities and independent 
researchers over the last century, from which some of the presently 
available research chemicals derive. One particularly notable researcher
 is Dr. Alexander Shulgin, who presented syntheses and pharmacological explorations of hundreds of substances in the books TiHKAL and PiHKAL (co-authored with Ann Shulgin), and has served as an expert witness for the defense in several court cases against manufacturers of psychoactive drugs. 
The majority of chemical suppliers sold research chemicals in 
bulk form as powder, not as pills, as selling in pill form would 
invalidate the claims that they were being sold for non-consumptive 
research. Active dosages vary widely from substance to substance, 
ranging from micrograms to hundreds of milligrams, but while it is 
critical for the end user to weigh doses with a precision scale, instead
 of guessing ("eyeballing"), many users did not do this and this led to 
many emergency room visits and several deaths, which were a prominent 
factor leading to the emergency scheduling of several substances and 
eventually Operation Web Tryp. Some compounds such as 2C-B and 5-Meo-DiPT
 did eventually increase in popularity to the point that they were sold 
in pill form to reach a wider market, and acquired popular street names 
("Nexus" and "Foxy," respectively). Once a chemical reaches this kind of
 popularity, it is usually just a matter of time before it is added to 
the list of scheduled (i.e., illegal) drugs.
The late 1990s and early 2000s also saw the first widespread use of novel anabolic steroids by athletes in competition. Steroids had been banned by the International Olympic Committee
 since 1976, but due to the large number of different anabolic agents 
available for human and veterinary use, the ability of laboratories to 
test for all available drugs had always lagged behind the ability of 
athletes to find new compounds to use. The introduction of increasingly 
formalised testing procedures, especially with the creation of the World Anti-Doping Agency
 in 1999, made it much more difficult for athletes to get away with 
using these drugs without detection, which then led to the synthesis of 
novel and potent anabolic steroid drugs such as tetrahydrogestrinone (THG), which were not detectable by the standard tests.
2005–2016
Popular designer drugs, 1990s-2016
While through recent history most designer drugs had been either 
opioids, hallucinogens, or anabolic steroids, the range of possible 
compounds is limited only by the scientific and patent literature, and 
recent years have been characterised by a broadening of the range of 
compounds sold as designer drugs. These have included a wide variety of 
designer stimulants such as geranamine, mephedrone, MDPV and desoxypipradrol, several designer sedatives such as methylmethaqualone and premazepam, and designer analogues of sildenafil (Viagra), which have been reported as active compounds in "herbal" aphrodisiac products. Designer cannabinoids are another recent development, with two compounds JWH-018 and (C8)-CP 47,497 initially found in December 2008 as active components of "herbal smoking blends" sold as legal alternatives to marijuana. Subsequently, a growing range of synthetic cannabinoid agonists have continued to appear, including by 2010, novel compounds such as RCS-4, RCS-8, and AB-001,
 which had never been reported in the literature, and appear to have 
been invented by designer drug manufacturers themselves. Another novel 
development is the use of research ligands for cosmetic rather than strictly recreational purposes, such as grey-market internet sales of the non-approved alpha-melanocyte-stimulating hormone tanning drugs known as melanotan peptides.
...what is new is the wide range of substances now being explored, the aggressive marketing of products that have been intentionally mislabelled, the growing use of the internet, and the speed at which the market reacts to control measures."
— EMCDDA director Wolfgang Goetz (November 2009).
Mephedrone and the cathinones marked somewhat of a turning point for designer drugs, turning them from little known, ineffective substances sold in head shops
 to powerful substances able to compete with classical drugs on the 
black market. Mephedrone especially experienced a somewhat meteoric rise
 in popularity in 2009
 and the resulting media panic resulted in its prohibition in multiple 
countries. Following this there was a considerable emergence of other 
cathinones which attempted to mimic the effects of mephedrone, and with a
 newly attracted customer base, plenty of money to drive innovation.
Subsequently, the market rapidly expanded, with more and more 
substances being detected every year. In 2009, the EMCDDA's early 
warning system discovered 24 new drugs. In 2010, it found another 41; in
 2011, another 49; and in 2012, there were 73 more. In 2013, a further 81 were identified:
 a total of 268 new drugs in just four years. These have not been 
limited to cathinones, with 35% being cannabinoids and the rest being 
composed of stimulants, benzodiazepines, psychedelics, dissociatives and
 to a lesser extent, every other class of drugs, even ibogoids and nootropics. As of 2017, the largest group of drugs being monitored by the EMCDDA is synthetic cannabinoids, with 169 different synthetic cannabinoids reported by December 2016.
Safety
The safety of research chemicals is untested and little if any research has been done on the toxicology or pharmacology of most of these drugs. Few, if any, human or animal studies
 have been done. Many research compounds have produced unexpected 
side-effects and adverse incidents due to the lack of screening for 
off-target effects prior to marketing; both bromo-dragonfly and mephedrone seem to be capable of producing pronounced vasoconstriction under some circumstances, which has resulted in several deaths, although the mechanism remains unclear. Substituted phenethylamines such as the 2C family and substituted amphetamines such as the DOx family have also caused a limited number of deaths.
Law
Due to the recent development of many designer drugs, laws banning or
 regulating their use have not been developed yet, and in recent cases 
novel drugs have appeared directly in response to legislative action, to
 replace a similar compound that had recently been banned.
 Many of the chemicals fall under the various drug analogue legislations
 in certain countries, but most countries have no general analogue act 
or equivalent legislation and so novel compounds may fall outside of the
 law after only minor structural modifications.
In the United States, the Controlled Substances Act was amended by the Controlled Substance Analogue Enforcement of 1986,
 which attempted to ban designer drugs pre-emptively by making it 
illegal to manufacture, sell, or possess chemicals that were 
substantially similar in chemistry and pharmacology to Schedule I or Schedule II drugs. 
Other countries have dealt with the issue differently. In some, 
the new drugs are banned as they become a concern, as in Germany, 
Canada, the United Kingdom, and Sweden. In Sweden, the police and 
customs from April 2011 may also seize drugs that are not on the list of
 drugs covered by the anti-drug laws if the police suspect that the 
purpose of the holding is related to drug abuse. Following a decision by
 a prosecutor, the police may destroy the seized drugs.
In Ireland, the Criminal Justice (Psychoactive Substances) Act 
2010 bans substances based on their psychoactive effect, and was 
introduced as a catch-all to address the time lag between new substances
 appearing and their being banned individually. Draft legislation before the UK parliament as of July 2015 (the Psychoactive Substances Bill 2015-16) adopts a similar approach.
Some countries, such as Australia, have enacted generic bans but 
based on chemical structure rather than psychoactive effect: if a 
chemical fits a set of rules regarding substitutions and alterations of 
an already-banned drug, then it too is banned.
 Brazil adopted the same model as Australia, in a recent ruling from 
ANVISA, which is responsible to define what constitute drugs. 
Temporary class drug
A temporary class drug is a relatively new status for controlled drugs, which has been adopted in some jurisdictions, notably New Zealand and the United Kingdom,
 to attempt to bring newly synthesized designer drugs under legal 
control. The controlled drug legislation in these jurisdictions requires
 drug scheduling decisions to follow an evidence-based process, where 
the harms of the drug are assessed and reviewed so that an appropriate 
legal status can be assigned. Since many designer drugs sold in recent 
years have had little or no published research that could help inform 
such a decision, they have been widely sold as "legal highs", often for 
months, before sufficient evidence accumulates to justify placing them 
on the controlled drug schedules.
Common names
In the UK to avoid being controlled by the Medicines Act, designer drugs such as mephedrone have been described as "plant food," despite the compounds having no history of being used for these purposes.
In the USA, similar descriptions ("bath salts" is the most common) have been used to describe mephedrone as well as methylone and methylenedioxypyrovalerone (MDPV). Combined with labeling that they are "not for human consumption," these descriptions are an attempt to skirt the Federal Analog Act which forbids drugs that are “substantially similar” to already classified drugs from being sold for human use.
Synthetic cannabinoids are known under a variety of names including K2, Spice, Black Mamba, Bombay Blue, Genie, Zohai, Banana Cream Nuke, Krypton, and Lava Red.
 They are often called “synthetic marijuana,” “herbal incense,” or 
“herbal smoking blends” and often labeled “not for human consumption.”


