An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist.
Ohmefentanyl is an extremely potent opioid analgesic drug which selectively binds to the µ-opioid receptor.
3-Methylfentanyl is an opioid analgesic that is an analog of fentanyl. 3-Methylfentanyl is one of the most potent opioids, estimated to be between 400 and 6000 times stronger than morphine, depending on which isomer is used.
Dimethylthiambutene is an opioid analgesic drug, most often used in veterinary medicine in Japan and to a lesser extent in other countries in the region and around the world. It is the most prominent and widely used of the thiambutenes, a series of open-chain opioids structurally related to methadone which are also called the thienyl derivative opioids which also includes diethylthiambutene and ethylmethylthiambutene, as well as the non-opioid cough suppressant tipepidine.
Ethylmethylthiambutene is an opioid analgesic drug from the thiambutene family, around 1.3x the potency of morphine. It is under international control under Schedule I of the UN Single Convention On Narcotic Drugs 1961, presumably due to high abuse potential.
Oripavine is an opioid and the major metabolite of thebaine. It is the parent compound from which a series of semi-synthetic opioids are derived, which includes the compounds etorphine and buprenorphine. Although its analgesic potency is comparable to morphine, it is not used clinically due to its severe toxicity and low therapeutic index. Due to its use in manufacture of strong opioids, oripavine is a controlled substance in some jurisdictions.
Cyprenorphine (M285), N-cyclo-propylmethyl-6,14-endoetheno-7α-(1-hydroxy-1-methylethyl)-6,7,8,14-tetrahydronororipavine, is an opioid drug. It is related to more well-known opioids such as buprenorphine, which is used as an analgesic and for the treatment of opioid addiction, and diprenorphine, which is used as an antidote to reverse the effects of other opioids. It is roughly 35 times as strong as nalorphine.
Allylprodine is an opioid analgesic that is an analog of prodine. It was discovered by Hoffman-La Roche in 1957 during research into the related drug pethidine. Derivatives were tested to prove the theory that phenolic & non-phenolic opioids bind at different sites of the opiate receptor.
Trimeperidine (Promedol) is an opioid analgesic that is an analogue of prodine. It was developed in the early 1950s in the USSR during research into the related drug pethidine.
Phenazocine is an opioid analgesic drug, which is related to pentazocine and has a similar profile of effects.
Propiram is a partial mu opioid receptor agonist and weak mu antagonist analgesic from the ampromide family of drugs related to other drugs such as phenampromide and diampromide. It was invented in 1963 in the United Kingdom by Bayer but was not widely marketed, although it saw some limited clinical use, especially in dentistry. Propiram reached Phase III clinical trials in the United States and Canada.
Phenampromide is an opioid analgesic from the ampromide family of drugs, related to other drugs such as propiram and diampromide. It was invented in the 1960s by American Cyanamid Co. Although never given a general release, it was trialled and 50mg codeine ≈ 60mg phenampromide. Tests on the 2 isomers showed that all of the analgesic effects were caused by the (S) isomer. In the book a 4-phenyl group added to the piperidine-ring produces a drug some x60 morphine. The potency derives from the fact that it overlays fentanyl. Like fentanyl, the addition of a 4-hydroxy group to the 4-piperidylphenyl derivative increases potency to x150 morphine for the racemic compound
7-PET is an opioid analgesic drug that has 300 times the potency of morphine by weight. It was discovered by K.W. Bentley and is related to the more well known oripavine derivative etorphine, which is used as a veterinary painkiller and anesthetic medication for the sedation of large animals such as elephants, giraffes, and rhinos. 7-PET itself has a 3-O-methyl ether which reduces potency, but the 3-OH derivative is around 2200 times more potent than morphine, almost the same potency as etorphine as a μ agonist, and unexpectedly the 3-hydrogen compound is also around the same potency of 2000 times morphine.
Viminol is an opioid analgesic developed by a team at the drug company Zambon in the 1960s. Viminol is based on the α-pyrryl-2-aminoethanol structure, unlike any other class of opioids.
C-8813 (thiobromadol) is a potent μ-opioid receptor agonist with a distinctive chemical structure which is not closely related to other established families of opioid drugs. The trans-isomer was found to be around 591 times more potent than morphine in animal studies. The same study assigned a potency of 504 times that of morphine to the related compound BDPC.
Piperidylthiambutene (Piperidinohton) is a synthetic opioid analgesic drug from the thiambutene family, which has around the same potency as morphine. Piperidylthiambutene is structurally distinct from fentanyl, its analogues, and other synthetic opioids previously reported. If sold or obtained for the purpose of human consumption it could be considered a controlled substance analogue in some countries such as the US, Australia and New Zealand. Piperidylthiambutene has been sold as a designer drug, first appearing in late 2018.
Pyrrolidinylthiambutene is an opioid analgesic drug from the thiambutene family with around 3/4 of the potency of morphine. It would be considered an illegal controlled substance analogue in some countries such as the US, Australia and New Zealand, but is legal in countries not possessing a controlled-substances-analog-act equivalent.
The Bentley compounds are a class of semi-synthetic opioids that were first synthesized by K. W. Bentley by Diels-Alder reaction of thebaine with various dienophiles. The compounds are also known as thevinols, orvinols, or bridged oripavine derivatives, due to the characteristic 6,14-endo-ethano- or etheno-bridge and substitution at the 7α position. Buprenorphine and etorphine are perhaps the best known of the family, which was the first series of extremely potent μ-opioid agonists, with some compounds in the series having over many thousands of times the analgesic potency of morphine.
PZM21 is an experimental opioid analgesic drug that is being researched for the treatment of pain. It is claimed to be a functionally selective μ-opioid receptor agonist which produces μ-opioid receptor mediated G protein signaling, with potency and efficacy similar to morphine, but with less β-arrestin 2 recruitment. However, recent reports highlight that this might be due to its low intrinsic efficacy, rather than functional selectivity or 'G protein bias' as initially reported. In tests on mice, PZM21 was slightly less potent than morphine or TRV130 as an analgesic, but also had significantly reduced adverse effects, with less constipation than morphine, and very little respiratory depression, even at high doses. This research was described as a compelling example of how modern high-throughput screening techniques can be used to discover new chemotypes with specific activity profiles, even at targets such as the μ-opioid receptor which have already been thoroughly investigated. More recent research has suggested however that at higher doses, PZM21 is capable of producing classic opioid side effects such as respiratory depression and development of tolerance and may have only limited functional selectivity.
Diphenpipenol is an opioid analgesic drug invented in the 1970s by Dainippon Pharmaceutical Co. It is chemically a 1-substituted-4-(1,2-diphenylethyl)piperazine derivative related to compounds such as MT-45 and AD-1211, but diphenpipenol is the most potent compound in the series, with the more active (S) enantiomer being around 105 times the potency of morphine in animal studies. This makes it a similar strength to fentanyl and its analogues, and consequently diphenpipenol can be expected to pose a significant risk of producing life-threatening respiratory depression, as well as other typical opioid side effects such as sedation, itching, nausea and vomiting.
