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Dezocine (DalganTM WY16225) is an opioid analgesic. First synthesized in 1970, it acts at mu-, delta-, and kappa-opioid receptors. Dezocine acts as a mixed agonist/antagonist of opioid receptors. It is related to other benzomorphans such as pentazocine, with a similar profile of effects that include analgesic action and euphoria. Unlike many other benzomorphans however, it is a silent antagonist of the κ-opioid receptor, and in accordance, does not produce side effects such as dysphoria or hallucinations at any dose.
Dezocine was patented by American Home Products Corp. in 1978. Clinical trials ran from 1979-1985, before its approval by the U.S. Food and Drug Administration (FDA) in 1986. As of 2011, dezocine's usage is discontinued in the United States.
Dezocine [(−)-13β-amino-5,6,7,8,9,10,11,12-octahydro-5α-methyl-5,11-methanobenxocyclodecen-31-ol, hydrobromide] is a pale white crystal powder. It has no apparent odor. The salt is soluble at 20 mg/ml, and a 2% solution has a pH of 4.6.
The synthesis of dezocine begins with the condensation of 1-methyl-7-methoxy-2-tetralone with 1,5-dibromopentane through use of NaH or potassium tertbutylate. This yields 1-(5-bromopentyl)-1-methyl-7-methoxy-2-tetralone, which is then cyclized with NaH to produce 5-methyl-3-methoxy-5,6,7,8,9,10,11,12-octahydro-5,11-methanobenzocyclodecen-13-one. The product is then treated with hydroxylamide hydrochloride, to yield an oxime. A reduction reaction in hydrogen gas produces an isomeric mixture, from which the final product (XII) is crystallized and cleaved with HBr.
Legal status in United States
As of 2011, dezocine is not used in the United States or Canada. It is not commercially available, nor is it offered as a prescribed analgesic for postoperative care. In China, it is commonly used after surgery.
Dezocine has an intramuscular bioavailability of 97%. It has a mean t1/2 α of fewer than two minutes, and its half-life is 2.2 hours. Its binding affinity varies with regards to the receptor type, as it acts as a partial agonist primarily on mu-opioid receptors. At kappa-opioid receptors, it acts as an antagonist. Overall, it has a high efficacy as an analgesic. With regards to its potency, it has a Bmax of 3326 fmol/mg of protein in HEK cells. Dezocine is five times as potent as pethidine and one-fifth as potent as butorphanol.
Dezocine is unusual among opiates as it is one of the only primary amines known to be an active opioid (along with bisnortilidine, an active metabolite of tilidine). It is a mixed agonist–antagonist as with other drugs in this class, and despite having a stronger respiratory depressant effect than morphine, dezocine shows a ceiling effect on its respiratory depressive action so above a certain dose this effect does not get any more severe.
Dezocine is generally administered intravenously. It can also be administered in intramuscular doses, and is given singularly rather than continuously. Dezocine has been found to be an effective painkiller comparable to meperidine (pethidine), and so is a more effective analgesic than pentazocine, but causes relatively more respiratory depression than pentazocine. It is a useful drug for the treatment of pain, but side effects such as dizziness limit its clinical application, and it can produce opioid withdrawal syndrome in patients already dependent on other opioids.
Dezocine is generally administered intravenously (as Dalgan™) to relieve post-operative pain in patients. Because of its high efficacy, it is often administered at a base dose of 0.1 mg/kg. Respiratory depression, a side-effect of dezocine, reaches a ceiling at 0.3-0.4 mg/kg. It has potent analgesic results, and greater pain-relieving ability than morphine, codeine, and pethidine.
Because decozine has mixed agonist/antagonist effects on mu-, delta-, and kappa-opioid receptors, it has a lowered dependence potential than purely agonistic opiates. It can be prescribed, therefore, in small doses over an extended period of time without causing patients to develop and sustain an addiction. Its efficacy as an analgesic is dose-dependent; however, it displays a ceiling effect in induced respiratory depression at 0.3-0.4 mg/kg.
Side effects at lower doses include mild gastrointestinal discomfort and dizziness. At relatively high doses, it has been found to produce hallucinations.[contradiction] It is often administered in post-operative laproscopy patients as an alternative to fentanyl.
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