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Chemical Nomenclature
Common names W-18
Systematic name 1-(4-Nitrophenylethyl)piperidylidene-2-(4-chlorophenyl)sulfonamide
Class Membership
Psychoactive class Unknown; sigma and TSPO (PBR) agonist
Chemical class Piperidine containing a sulfonamide group
Routes of Administration

WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.

Common W-18 has little to no dosing information.
Total W-18 has little to no duration information.

DISCLAIMER: PW's dosage information is gathered from users and resources for educational purposes only. It is not a recommendation and should be verified with other sources for accuracy.

Summary sheet: W-18

W-18, or 1-(4-Nitrophenylethyl)piperidylidene-2-(4-chlorophenyl)sulfonamide, is an extremely potent opioid analgesic with little to no history of human use. This compound is claimed to be 10,000x more potent than morphine and 1000x more potent than fentanyl.[1] Although commonly reported as an opioid in the popular press, it is not known how the drug works as its distinctive structure differs somewhat to known opioid drugs.[2] It was invented at the University of Alberta[3] by the chemists Edward Knaus, Brent Warren and Theodore Ondrus in 1981.[4][5]

However, recent information suggests that W-18, a street drug feared to be stronger than any opioid known to science, turns out not be an opioid at all. W-18, an experimental pain medicine first developed at the University of Alberta in Edmonton in the 1980s, doesn’t even appear to provide relief in animal pain models. These findings appeared July 24, 2016 in a preprint report (PDF) in bioRxiv (pronounced “Bioarchive”), a non-peer-reviewed resource of Cold Spring Harbor Laboratories designed to rapidly disseminate critical research findings.

The comprehensive study not only showed the lack of opioid effects of W-18 or a related chemical called W-15, but also showed that human or mouse metabolites of the chemicals had no effect on human or mouse opioid receptors. More surprisingly, a receptorome-wide screen showed no substantial effect of the compounds or metabolites on any psychoactive drug receptor. The study marks a rare case where a potentially lethal drug of abuse is likely to be far less of a public health risk than originally believed.[6]

The compound's toxicity is not fully characterized, but its potency gives it potential for fatal abuse.



This chemistry section is incomplete.

You can help by adding to it.


Due to the lack of research regarding the substance, all discussion regarding the pharmacology of it is purely based on its subjective similarities to other opioids such as fentanyl and heroin.

The recreational effects of this compound likely occurs because opioids structurally mimic endogenous endorphins which are naturally found within the body and also work upon the μ-opioid receptor set. The way in which opioids structurally mimic these natural endorphins results in their euphoria, pain relief and anxiolytic effects. This is because endorphins are responsible for reducing pain, causing sleepiness, and feelings of pleasure. They can be released in response to pain, strenuous exercise, orgasm, or general excitement.

Subjective effects

This subjective effects section is a stub.

As such, it is still in progress and may contain incomplete or wrong information.

You can help by expanding or correcting it.

Toxicity and harm potential

Non-medical use of W-18 by individuals without opiate tolerance is extremely dangerous and has resulted in numerous deaths.[7] It is potentially fatal at heavy dosages and even those with opiate tolerances are at high risk for overdoses. Once the W-18 is in the user's system, it is likely extremely difficult to stop its course because it is still not yet known if naloxone, the standard emergency antidote for opioids, is effective against W-18.[8].

Due to the extremely high strength of pure W-18 powder, it is very difficult to dilute appropriately, and often the resulting mixture may be far too strong and, therefore, very dangerous. If one has decided to consume this compound despite the risks, they should use volumetric liquid dosing to measure the desired amount as milligram scales cannot weigh such a potent compound with accuracy. It is important to consider that particular care must be taken with W-18 due to its extreme potency and ability to be absorbed through the skin. This means that simply unintentionally spilling a very small amount of the drug on one's skin could result in a fatal overdose.

Heavy dosages of W-18 can result in respiratory depression, leading onto fatal or dangerous levels of anoxia (oxygen deprivation). This occurs because the breathing reflex is suppressed by agonism of µ-opioid receptors proportional to the dosage consumed. It is also potentially lethal when mixed with depressants like alcohol or benzodiazepines.

W-18 can cause nausea and vomiting; a significant number of deaths attributed to opioid overdose are caused by aspiration of vomit by an unconscious victim. This is when an unconscious or semi-conscious user who is lying on their back vomits into their mouth and unknowingly suffocates. It can be prevented by ensuring that one is lying on their side with their head tilted downwards so that the airways cannot be blocked in the event of vomiting while unconscious (also known as the recovery position). In case of an overdose, it is advised to administer a dose of naloxone intravenously or intramuscularly to reverse the effects of opioid agonism (however, it is still not yet known if naloxone is effective against W-18).[9].

It is strongly recommended that one use harm reduction practices when using this drug.

Tolerance and addiction potential

As with other opioids, the chronic use of W-18 can likely be considered extremely addictive with a high potential for abuse and is probably capable of causing psychological dependence among certain users. When addiction has developed, cravings and withdrawal symptoms may occur if a person suddenly stops their usage.

Tolerance to many of the effects of W-18 likely develop with prolonged and repeated use. This results in users having to administer increasingly large doses to achieve the same effects. After that, it likely takes about 3 - 7 days for the tolerance to be reduced to half and 1 - 2 weeks to be back at baseline (in the absence of further consumption). W-18 likely presents cross-tolerance with all other opioids, meaning that after the consumption of W-18 all opioids will have a reduced effect.

Dangerous interactions

Although many drugs are safe on their own, they can become dangerous and even life-threatening when combined with other substances. The list below contains some common potentially dangerous combinations, but may not include all of them. Certain combinations may be safe in low doses of each but still increase the potential risk of death. Independent research should always be done to ensure that a combination of two or more substances is safe before consumption.

  • Depressants (1,4-Butanediol, 2m2b, alcohol, barbiturates, benzodiazepines, GHB/GBL, methaqualone) - This combination can result in dangerous or even fatal levels of respiratory depression. These substances potentiate the muscle relaxation, sedation and amnesia caused by one another and can lead to unexpected loss of consciousness at high doses. There is also an increased risk of vomiting during unconsciousness and death from the resulting suffocation. If this occurs, users should attempt to fall asleep in the recovery position or have a friend move them into it.
  • Dissociatives - This combination can result in an increased risk of vomiting during unconsciousness and death from the resulting suffocation. If this occurs, users should attempt to fall asleep in the recovery position or have a friend move them into it.
  • Stimulants - It is dangerous to combine W-18, a depressant, with stimulants due to the risk of excessive intoxication. Stimulants decrease the sedative effect of W-18, which is the main factor most people consider when determining their level of intoxication. Once the stimulant wears off, the effects of W-18 will be significantly increased, leading to intensified disinhibition as well as other effects. If combined, one should strictly limit themselves to taking a certain amount of W-18.

Legal issues


This legality section is a stub.

As such, it may contain incomplete or wrong information. You can help by expanding it.

  • Sweden - W-18 is illegal as of 26 January 2016.[10]
  • Canada - Health Canada proposed in February 2016 to list W-18 in Schedule I of the Controlled Drugs and Substances Act, which would make it illegal except for authorized prescription use, similar to fentanyl and other opioids.[11] Details of the proposal are in the Canada Gazette.[12]
  • USA - W-18 is not currently regulated under the Controlled Drug and Substances Act and can be manufactured and bought freely according to the B.C. Centre for Disease Control.
  • United Kingdom - It is illegal to produce, supply, or import this drug under the Psychoactive Substance Act, which came into effect on May 26th, 2016.[13]

External links


  1. Everything We Know So Far About W-18, the Drug That’s 10,000 Times More Powerful Than Morphine (Vice) |
  2. W-18, The High-Potency Research Chemical Making News: What It Is And What It Isn't (Forbes) |
  3. Street drug W-18 is highly lethal, and still legal (CBC News) |
  4. "Patent US 4468403 - Analgesic substituted piperidylidene-2-sulfon(cyan)amide derivatives" |
  7. Everything We Know So Far About W-18, the Drug That’s 10,000 Times More Powerful Than Morphine |
  8. What we know about W-18, a drug ‘100 times more powerful than fentanyl’ (Global News) |
  9. What we know about W-18, a drug ‘100 times more powerful than fentanyl’ (Global News) |
  10. 31 nya ämnen kan klassas som narkotika eller hälsofarlig vara |
  11. Consultation - Proposal regarding the scheduling of W-18 under the Controlled Drugs and Substances Act and its Regulations |
  13. Psychoactive Substances Act 2016 ( |