Endorphins are peptides produced in the brain that block the perception of pain and increase feelings of wellbeing. They are produced and stored in the pituitary gland of the brain. Endorphins are endogenous painkillers often produced in the brain and adrenal medulla during physical exercise or orgasm and inhibit pain, muscle cramps, and relieve stress.
Carfentanil or carfentanyl, sold under the brand name Wildnil, is an extremely potent opioid analgesic used in veterinary medicine to anesthetize large animals such as elephants and rhinoceroses. It is typically administered in this context by tranquilizer dart. Carfentanil has also been used in humans to image opioid receptors. It has additionally been used as a recreational drug, typically by injection, insufflation, or inhalation. Deaths have been reported in association with carfentanil.
Nalbuphine, sold under the brand names Nubain among others, is an opioid analgesic which is used in the treatment of pain. It is given by injection into a vein, muscle, or fat.
The nociceptin opioid peptide receptor (NOP), also known as the nociceptin/orphanin FQ (N/OFQ) receptor or kappa-type 3 opioid receptor, is a protein that in humans is encoded by the OPRL1 gene. The nociceptin receptor is a member of the opioid subfamily of G protein-coupled receptors whose natural ligand is the 17 amino acid neuropeptide known as nociceptin (N/OFQ). This receptor is involved in the regulation of numerous brain activities, particularly instinctive and emotional behaviors. Antagonists targeting NOP are under investigation for their role as treatments for depression and Parkinson's disease, whereas NOP agonists have been shown to act as powerful, non-addictive painkillers in non-human primates.
Dihydroetorphine was developed by K. W. Bentley at McFarlan-Smith in the 1960s and is a potent opioid analgesic used mainly in China. It is a derivative of the better-known opioid etorphine, a very potent veterinary painkiller and anesthetic medication used primarily for the sedation of large animals such as elephants, giraffes, and rhinos.
Dezocine, sold under the brand name Dalgan, is an atypical opioid analgesic which is used in the treatment of pain. It is used by intravenous infusion and intramuscular injection.
Proglumide, sold under the brand name Milid, is a drug that inhibits gastrointestinal motility and reduces gastric secretions. It acts as a cholecystokinin antagonist, which blocks both the CCKA and CCKB subtypes. It was used mainly in the treatment of stomach ulcers, although it has now been largely replaced by newer drugs for this application.
RB-101 is a drug that acts as an enkephalinase inhibitor, which is used in scientific research.
14-Methoxymetopon is an experimental opioid drug developed by a team led by Professor Helmut Schmidhammer at the University of Innsbruck in the mid-1990s. It is a derivative of metopon in which a methoxy group has been inserted at the 14-position. It is a highly potent analgesic drug that is around 500 times stronger than morphine when administered systemically; however, when given spinally or supraspinally, it exhibits analgesic activity up to a million fold greater than morphine. It binds strongly to the μ-opioid receptor and activates it to a greater extent than most similar opioid drugs. This produces an unusual pharmacological profile, and although 14-methoxymetopon acts as a potent μ-opioid full agonist in regard to some effects such as analgesia, a ceiling effect is seen on other effects such as constipation and respiratory depression which is believed to involve interaction with the κ-opioid receptor
Azaprocin is a drug which is an opioid analgesic with approximately ten times the potency of morphine, and a fast onset and short duration of action. It was discovered in 1963, but has never been marketed.
SC-17599 is a steroid derivative drug discovered in 1968 which acts as a selective μ-opioid receptor agonist, with little or no affinity for the δ-opioid or κ-opioid receptors. It is an active analgesic in vivo, more potent than codeine or pethidine but slightly less potent than morphine, and produces similar effects to morphine in animals but with less sedation
Oxymorphazone is an opioid analgesic drug related to oxymorphone. Oxymorphazone is a potent and long acting μ-opioid agonist which binds irreversibly to the receptor, forming a covalent bond which prevents it from detaching once bound. This gives it an unusual pharmacological profile, and while oxymorphazone is only around half the potency of oxymorphone, with higher doses the analgesic effect becomes extremely long lasting, with a duration of up to 48 hours. However, tolerance to analgesia develops rapidly with repeated doses, as chronically activated opioid receptors are rapidly internalised by β-arrestins, similar to the results of non-covalent binding by repeated doses of agonists with extremely high binding affinity such as lofentanil.
Alazocine, also known more commonly as N-allylnormetazocine (NANM), is a synthetic opioid analgesic of the benzomorphan family related to metazocine, which was never marketed. In addition to its opioid activity, the drug is a sigma receptor agonist, and has been used widely in scientific research in studies of this receptor. Alazocine is described as a potent analgesic, psychotomimetic or hallucinogen, and opioid antagonist. Moreover, one of its enantiomers was the first compound that was found to selectively label the σ1 receptor, and led to the discovery and characterization of the receptor.
An opiate is an alkaloid substance derived from opium. It differs from the similar term opioid in that the latter is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain. Opiates are alkaloid compounds naturally found in the opium poppy plant Papaver somniferum. The psychoactive compounds found in the opium plant include morphine, codeine, and thebaine. Opiates have long been used for a variety of medical conditions, with evidence of opiate trade and use for pain relief as early as the eighth century AD. Most opiates are considered drugs with moderate to high abuse potential and are listed on various "Substance-Control Schedules" under the Uniform Controlled Substances Act of the United States of America.
U-69,593 is a drug which acts as a potent and selective κ1-opioid receptor agonist. In animal studies it has been shown to produce antinociception, anti-inflammation, anxiolysis, respiratory depression, and diuresis, while having little effect on gastrointestinal motility. It also inhibits the peripheral, though not central secretion of oxytocin and vasopressin in rats.
MT-45 (IC-6) 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, which is structurally unrelated to most other opioid drugs. Racemic MT-45 has around 80% the potency of morphine, with almost all opioid activity residing in the (S) enantiomer. It has been used as a lead compound from which a large family of potent opioid drugs have been developed, including full agonists, partial agonists, and antagonists at the three main opioid receptor subtypes. Fluorinated derivatives of MT-45 such as 2F-MT-45 are significantly more potent as μ-opioid receptor agonists, and one of its main metabolites 1,2-diphenylethylpiperazine also blocks NMDA receptors.
IBNtxA, or 3-iodobenzoyl naltrexamine, is an atypical opioid analgesic drug derived from naltrexone. In animal studies it produces potent analgesic effects that are blocked by levallorphan and so appear to be μ-opioid mediated, but it fails to produce constipation or respiratory depression, and is neither rewarding or aversive in conditioned place preference protocols. These unusual properties are thought to result from agonist action at a splice variant or heterodimer of the μ-opioid receptor, rather than at the classical full length form targeted by conventional opioid drugs.
Cebranopadol is an opioid analgesic of the benzenoid class which is currently under development internationally by Grünenthal, a German pharmaceutical company, and its partner Depomed, a pharmaceutical company in the United States, for the treatment of a variety of different acute and chronic pain states. As of November 2014, it is in phase III clinical trials.
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.
Bucinnazine is an opioid analgesic drug that was widely used in China to treat pain in cancer patients as of 1986. It is one of the most potent compounds among a series of piperazine-amides first synthesized and reported in Japan in the 1970s. Bucinnazine has analgesic potency comparable to that of morphine, but with a relatively higher therapeutic index.
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