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Ligand-Free Signaling of G-Protein-Coupled Receptors: Relevance to μ Opioid Receptors in Analgesia and Addiction. Molecules 2022; 27:molecules27185826. [PMID: 36144565 PMCID: PMC9503102 DOI: 10.3390/molecules27185826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 09/04/2022] [Accepted: 09/06/2022] [Indexed: 11/17/2022] Open
Abstract
Numerous G-protein-coupled receptors (GPCRs) display ligand-free basal signaling with potential physiological functions, a target in drug development. As an example, the μ opioid receptor (MOR) signals in ligand-free form (MOR-μ*), influencing opioid responses. In addition, agonists bind to MOR but can dissociate upon MOR activation, with ligand-free MOR-μ* carrying out signaling. Opioid pain therapy is effective but incurs adverse effects (ADRs) and risk of opioid use disorder (OUD). Sustained opioid agonist exposure increases persistent basal MOR-μ* activity, which could be a driving force for OUD and ADRs. Antagonists competitively prevent resting MOR (MOR-μ) activation to MOR-μ*, while common antagonists, such as naloxone and naltrexone, also bind to and block ligand-free MOR-μ*, acting as potent inverse agonists. A neutral antagonist, 6β-naltrexol (6BN), binds to but does not block MOR-μ*, preventing MOR-μ activation only competitively with reduced potency. We hypothesize that 6BN gradually accelerates MOR-μ* reversal to resting-state MOR-μ. Thus, 6BN potently prevents opioid dependence in rodents, at doses well below those blocking antinociception or causing withdrawal. Acting as a ‘retrograde addiction modulator’, 6BN could represent a novel class of therapeutics for OUD. Further studies need to address regulation of MOR-μ* and, more broadly, the physiological and pharmacological significance of ligand-free signaling in GPCRs.
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Osborn MD, Lowery JJ, Skorput AGJ, Giuvelis D, Bilsky EJ. In vivo characterization of the opioid antagonist nalmefene in mice. Life Sci 2010; 86:624-30. [PMID: 20159022 DOI: 10.1016/j.lfs.2010.02.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 02/02/2010] [Accepted: 02/08/2010] [Indexed: 10/19/2022]
Abstract
AIMS The current study assessed the in vivo antagonist properties of nalmefene using procedures previously used to characterize the opioid antagonists naloxone, naltrexone, 6beta-naltrexol and nalbuphine. MAIN METHODS ICR mice were used to generate antagonist dose-response curves with intraperitoneal (i.p.) nalmefene against fixed A(90) doses of morphine in models of morphine-stimulated hyperlocomotion and antinociception. Additional dose-response curves for antagonist precipitated opioid withdrawal were run in mice treated acutely (100mg/kg, s.c., -4h) or chronically (75mg pellet, s.c., -72h) with morphine. Comparisons were made between antagonist potency and degree of precipitated withdrawal. KEY FINDINGS Nalmefene produced dose- and time-related antagonism of morphine-induced increases in locomotor activity with a calculated ID(50) (and 95% confidence interval) of 0.014 (0.007-0.027)mg/kg. Nalmefene produced rapid reversal of morphine-induced locomotor activity (5.1min for 50% reduction in morphine effect). A 0.32mg/kg dose of nalmefene produced blockade of morphine-induced antinociception in the 55 degrees C tail-flick test that lasted approximately 2h. Nalmefene was able to potently precipitate withdrawal in mice treated acutely or chronically with morphine. SIGNIFICANCE These results demonstrate that nalmefene is similar to naloxone and naltrexone with respect to its in vivo pharmacology in mice. Specifically, nalmefene produces potent antagonism of morphine agonist effects while precipitating severe withdrawal. The compound has a slower onset and longer duration of action compared to naloxone and naltrexone. The data allows for a more complete preclinical comparison of nalmefene against other opioid antagonists including the putative opioid neutral antagonist 6beta-naltrexol.
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Affiliation(s)
- Melissa D Osborn
- Department of Nurse Anesthesia, Westbrook College of Health Professions, University of New England, Portland, ME 04103, United States
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Divin MF, Holden Ko MC, Traynor JR. Comparison of the opioid receptor antagonist properties of naltrexone and 6 beta-naltrexol in morphine-naïve and morphine-dependent mice. Eur J Pharmacol 2008; 583:48-55. [PMID: 18275956 DOI: 10.1016/j.ejphar.2008.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Revised: 12/20/2007] [Accepted: 01/15/2008] [Indexed: 11/17/2022]
Abstract
It has been proposed that on chronic morphine treatment the micro-opioid receptor becomes constitutively active, and as a consequence, the opioid withdrawal response arises from a reduction in the level of this constitutively active receptor. In support of this, the putative micro-opioid receptor inverse agonist naltrexone has been shown to precipitate more severe withdrawal behavior in mice than the putative neutral receptor antagonist 6 beta-naltrexol. In the present study naltrexone and 6 beta-naltrexol were compared in NIH Swiss mice to test the hypothesis that their differential ability to precipitate withdrawal is due to differences in their in vivo opioid receptor antagonist potencies caused by differential access to micro-opioid receptors in the central nervous system and not necessarily by intrinsic differences in their opioid receptor activity. In naïve mice both compounds had similar potencies to antagonize morphine-induced antinociception in the hot plate and warm-water tail-withdrawal assays when measured under equilibrium conditions and afforded similar calculated apparent in vivo micro-opioid receptor affinities. In morphine-dependent mice both compounds precipitated withdrawal jumping but naltrexone was between 10- and 100-fold more potent than 6 beta-naltrexol. A similar potency difference was seen for other withdrawal behaviors. Both naltrexone and 6 beta-naltrexol at 1 mg/kg reversed antinociception induced by the long-lasting micro-opioid receptor agonist BU72 in the warm-water tail-withdrawal assay, but antagonism by naltrexone was 6-fold more rapid in onset at equal doses. Since the compounds have similar affinity for the micro-opioid receptor in vivo, the results suggest that the differences observed between the ability of naltrexone and 6 beta-naltrexol to precipitate withdrawal in the mouse may be explained by differential onset of receptor antagonist action.
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MESH Headings
- Animals
- Binding, Competitive/drug effects
- Data Interpretation, Statistical
- Dose-Response Relationship, Drug
- Male
- Mice
- Mice, Inbred ICR
- Morphinans/antagonists & inhibitors
- Morphinans/pharmacology
- Morphine/pharmacology
- Morphine Dependence/metabolism
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Narcotic Antagonists/pharmacology
- Narcotics/pharmacology
- Pain Measurement/drug effects
- Pyrroles/antagonists & inhibitors
- Pyrroles/pharmacology
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Substance Withdrawal Syndrome/psychology
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Affiliation(s)
- Mary F Divin
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109-5632, USA
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Ko MCH, Divin MF, Lee H, Woods JH, Traynor JR. Differential in Vivo Potencies of Naltrexone and 6β-Naltrexol in the Monkey. J Pharmacol Exp Ther 2005; 316:772-9. [PMID: 16258020 DOI: 10.1124/jpet.105.094409] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
6beta-Naltrexol is the major metabolite of the opioid receptor antagonist, naltrexone, in humans. However, there are no functional studies of 6beta-naltrexol in primates. The aim of this study was to compare the in vitro and in vivo potencies of naltrexone and 6beta-naltrexol in rhesus monkeys. Affinity and potency were determined using radioligand displacement and stimulation of 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) binding in monkey brain membranes. In vivo apparent pA(2) analysis was applied to compare the mu-opioid receptor (MOR) antagonist potency of both compounds in nondependent monkeys. In addition, the potencies of both compounds were determined in precipitating withdrawal manifested by increased respiratory parameters in acute morphine-dependent monkeys. In vitro assays revealed that naltrexone displayed 2-fold higher affinity and potency than 6beta-naltrexol for the MOR binding site and for MOR agonist-stimulated [(35)S]GTPgammaS binding, respectively. 6beta-Naltrexol (0.32-3.2 mg/kg) dose-dependently produced parallel rightward shifts of the dose-response curve of alfentanil-induced antinociception. Nevertheless, the apparent pA(2) value of 6beta-naltrexol (6.5) was 100-fold less potent than that of naltrexone (8.5) determined previously. 6beta-Naltrexol was also less potent than naltrexone in antagonizing other MOR-mediated effects including respiratory depression and itch/scratching. Naltrexone (0.0032-0.032 mg/kg) and 6beta-naltrexol (0.32-3.2 mg/kg) retained the same potency difference in precipitating withdrawal to a similar degree. Furthermore, 6beta-naltrexol failed to block naltrexone-precipitated withdrawal in morphine-dependent monkeys. These results indicate that naltrexone and 6beta-naltrexol display similar pharmacological actions with a large in vivo potency difference in monkeys such that 6beta-naltrexol may play a minimal role in the therapeutic or antagonist effects of naltrexone in primates.
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Affiliation(s)
- M C Holden Ko
- Department of Pharmacology, University of Michigan, Ann Arbor, 48109-0632, USA.
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Paudel KS, Nalluri BN, Hammell DC, Valiveti S, Kiptoo P, Hamad MO, Crooks PA, Stinchcomb AL. Transdermal Delivery of Naltrexone and its Active Metabolite 6-β-Naltrexol in Human Skin in Vitro and Guinea Pigs in Vivo. J Pharm Sci 2005; 94:1965-75. [PMID: 16052561 DOI: 10.1002/jps.20398] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The aim of the present study was to evaluate the transdermal delivery of 6-beta-naltrexol (NTXOL), the active metabolite of naltrexone (NTX), across human skin and guinea pig skin in vitro and in hairless guinea pigs in vivo. NTXOL may be responsible for much of NTX's pharmacologic activity. In vitro diffusion studies on NTXOL were compared with similar studies on NTX using a formulation of propylene glycol and buffer in a flow-through diffusion cell system. In vivo guinea pig studies were carried out involving topical application of both drugs in patches containing identical formulations. The in vitro flux of NTX was about 2.3- and 5.6-fold higher than for NTXOL across guinea pig skin and human skin, respectively. NTXOL lag times were longer than NTX in both skin types. In vivo studies in guinea pigs showed that the steady-state plasma level of NTX was twofold greater than NTXOL, which correlated well with in vitro data. The results of the present study indicated that substantial levels of NTX and NTXOL could be delivered via the transdermal route, although the plasma levels of NTXOL were significantly less than NTX. Further transdermal formulation development will be investigated for permeation enhancement.
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Affiliation(s)
- Kalpana S Paudel
- Department of Pharmaceutical Sciences, University of Kentucky College of Pharmacy, Lexington, Kentucky 40536-0082, USA
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Stromberg MF, Rukstalis MR, Mackler SA, Volpicelli JR, O'Brien CP. A comparison of the effects of 6-beta naltrexol and naltrexone on the consumption of ethanol or sucrose using a limited-access procedure in rats. Pharmacol Biochem Behav 2002; 72:483-90. [PMID: 11900823 DOI: 10.1016/s0091-3057(02)00721-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We recently reported that 6-beta naltrexol, the major metabolite of naltrexone in humans, reduced ethanol consumption in rats. Two new experiments were designed to compare 6-beta naltrexol and naltrexone across three dose levels on an ethanol or sucrose baseline using a limited-access procedure in Wistar rats. The results of Experiment 1 showed that both 6-beta naltrexol and naltrexone reduced ethanol consumption across a range of doses. An in vivo assay showed that naltrexone was approximately 25 times more potent than 6-beta naltrexol at comparable ED50 doses. In addition, there was no indication of systematic development of tolerance to the effect of either drug across the 4 days of drug administration. In Experiment 2, both 6-beta naltrexol and naltrexone reduced the consumption of a sucrose solution using a limited-access procedure. The implications of these data for the development of pharmacotherapeutic agents capable of reducing drinking in recovering alcoholics are discussed.
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Affiliation(s)
- Michael F Stromberg
- Department of Psychiatry, Center For Studies of Addiction, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Porter SJ, Somogyi AA, White JM. In vivo and in vitro potency studies of 6beta-naltrexol, the major human metabolite of naltrexone. Addict Biol 2002; 7:219-25. [PMID: 12006217 DOI: 10.1080/135562102200120442] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Naltrexone, a mu opioid receptor antagonist, is used in the treatment of opioid and alcohol dependence. Naltrexone's longer duration of action compared to naloxone has been considered to be due partly to its major human metabolite, 6beta-naltrexol. To date, no studies have examined the in vitro or in vivo potency of 6beta-naltrexol compared to naltrexone and naloxone. In the electrically-stimulated guinea pig ileum, 6beta-naltrexol was more potent (K(i) = 94 +/- 25 pM), than naloxone (420 +/- 150 pM), and naltrexone (265 +/- 101 pM). In vivo comparative potencies were assessed using the mouse hotplate test and morphine (agonist), with doses of the antagonists from 0.001 to 30 mg/kg. The order of potency was naltrexone (ID(50) 7 microg/kg), naloxone (ID(50) 16 microg/kg) and 6beta-naltrexol (ID(50) 1300 microg/kg). Antagonist ID(50) doses were then administered at 45, 90, 120, 180 and 1080 minutes prior to morphine administration. The duration of antagonist activity to decrease by 50% was 80, 125 and 340 minutes for naltrexone, naloxone and 6beta-naltrexol, respectively. 6beta-naltrexol is highly potent in the guinea pig ileum, but much less so in vivo after an acute dose. However, the potency of 6beta-naltrexol in vivo is time-dependent, and it has a longer duration of action than naloxone and naltrexone, consistent with a pharmacokinetic longer terminal half-life. Therefore, 6beta-naltrexol is likely to contribute to the efficacy of naltrexone in humans.
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Affiliation(s)
- Susan J Porter
- Department of Clinical and Experimental Pharmacology, Adelaide University, Adelaide 5005, Australia.
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Wang D, Raehal KM, Bilsky EJ, Sadée W. Inverse agonists and neutral antagonists at mu opioid receptor (MOR): possible role of basal receptor signaling in narcotic dependence. J Neurochem 2001; 77:1590-600. [PMID: 11413242 DOI: 10.1046/j.1471-4159.2001.00362.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mu opioid receptor, MOR, displays spontaneous agonist-independent (basal) G protein coupling in vitro. To determine whether basal MOR signaling contributes to narcotic dependence, antagonists were tested for intrinsic effects on basal MOR signaling in vitro and in vivo, before and after morphine pretreatment. Intrinsic effects of MOR ligands were tested by measuring GTPgammaS binding to cell membranes and cAMP levels in intact cells. beta-CNA, C-CAM, BNTX, and nalmefene were identified as inverse agonists (suppressing basal MOR signaling). Naloxone and naltrexone were neutral antagonists (not affecting basal signaling) in untreated cells, whereas inverse agonistic effects became apparent only after morphine pretreatment. In contrast, 6alpha- and 6beta-naltrexol and -naloxol, and 6beta-naltrexamine were neutral antagonists regardless of morphine pretreatment. In an acute and chronic mouse model of morphine-induced dependence, 6beta-naltrexol caused significantly reduced withdrawal jumping compared to naloxone and naltrexone, at doses effective in blocking morphine antinociception. This supports the hypothesis that naloxone-induced withdrawal symptoms result at least in part from suppression of basal signaling activity of MOR in morphine-dependent animals. Neutral antagonists have promise in treatment of narcotic addiction.
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Affiliation(s)
- D Wang
- Department of Biopharmaceutical Sciences and Pharmaceutical Chemistry, and Wheeler Center for Neurobiology of Addiction, University of California San Francisco, 94143-0446, USA
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Abstract
Several psychotropic and neurotropic agents are useful in treating patients with skin diseases such as obsessive compulsive skin manipulation, delusions of parasitosis, generalized pruritus, and post-herpetic neuralgia. The mechanism of action of these agents is based on their interaction with central and peripheral neuronal receptors. The medications discussed in this article include the tricyclic antidepressants, serotonin reuptake inhibitors, naltrexone, pimozide, and gabapentin. The pharmacology, mechanism of action, adverse effects, drug interactions, and monitoring guidelines are outlined for each of these drugs.
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Affiliation(s)
- H Tennyson
- Section of Dermatology, University of Arizona College of Medicine, Tucson, Arizona, USA
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Rukstalis MR, Stromberg MF, O'Brien CP, Volpicelli JR. 6-beta-Naltrexol Reduces Alcohol Consumption in Rats. Alcohol Clin Exp Res 2000. [DOI: 10.1111/j.1530-0277.2000.tb04580.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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6-??-Naltrexol Reduces Alcohol Consumption in Rats. Alcohol Clin Exp Res 2000. [DOI: 10.1097/00000374-200010000-00019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Hanes SD, Franklin M, Kuhl DA, Headley AS. Prolonged opioid antagonism with naloxone in chronic renal failure. Pharmacotherapy 1999; 19:897-901. [PMID: 10417042 DOI: 10.1592/phco.19.10.897.31557] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Respiratory depression secondary to morphine intoxication occurred in an elderly patient with chronic renal failure (CRF). It was reversed with a continuous infusion of naloxone. Approximately 11 hours after the infusion was discontinued, the patient relapsed into respiratory depression consistent with opioid intoxication. He was rechallenged with a naloxone infusion with resolution of the opioid effects. This case suggests prolonged antagonism of opioid effects inconsistent with naloxone's reported pharmacologic effects. Serum naloxone concentrations measured after the end of the infusion suggest that the drug's pharmacokinetics were significantly altered. Further research is necessary to characterize pharmacokinetic changes that occur in CRF. In the absence of this information, similar patients should be closely monitored for relapse of respiratory depression after naloxone is discontinued.
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Affiliation(s)
- S D Hanes
- Department of Clinical Pharmacy, University of Tennessee, Memphis 38163, USA
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King AC, Volpicelli JR, Gunduz M, O'Brien CP, Kreek MJ. Naltrexone Biotransformation and Incidence of Subjective Side Effects: A Preliminary Study. Alcohol Res 1997. [DOI: 10.1111/j.1530-0277.1997.tb03856.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Bradberry JC, Raebel MA. Continuous infusion of naloxone in the treatment of narcotic overdose. DRUG INTELLIGENCE & CLINICAL PHARMACY 1981; 15:945-50. [PMID: 7338189 DOI: 10.1177/106002808101501205] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Based on the pharmacokinetic parameters of naloxone and the clinical studies discussed in this paper, it is evident that naloxone infusion may be useful in cases of opiate overdose. The infusion protocol presented in Appendix I was formulated based on the pharmacokinetic data available from the literature including Nelson's animal data. An infusion of naloxone was used with apparent success in the two cases presented. Both patients presented with narcotic overdose; although immediate patient history could not be obtained, the presentations were classic for narcotic overdose. It is of note that it may be possible to keep a patient from relapsing into narcosis after overdose by the use of naloxone infusion. Additionally, the extreme safety of naloxone is certainly an advantage with any administration technique. We feel that the administration of continuous infusion of naloxone is an especially important advance in the overdose treatment of longer-acting agents such as methadone, as well as of other narcotics. Therefore, it is recommended that further clinical trials of naloxone by infusion be undertaken, as suggested by J. Nelson, et al. (A protocol for treatment with continuous infusion of naloxone [Narcan] in selected cases of opiate [narcotic] overdose. Austin: University of Texas; May, 1976, unpublished), to further document the effectiveness of an infusion of naloxone in narcotic overdose.
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Cone EJ. General procedure for the isolation and identification of 6-alpha- and 6-beta-hydroxy metabolites of narcotic agonists and antagonists with a hydromorphone structure. J Chromatogr A 1976; 129:355-61. [PMID: 1002794 DOI: 10.1016/s0021-9673(00)87795-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In order to aid in the elucidation of the metabolism of drugs containing the hydromorphone structure, a method is described for isolation from urine, separation and identification of the 6-alpha- and 6-beta-hydroxy metabolites. The samples were acid-hydrolyzed, extracted, and separated by thin-layer chromatography. The zone containing the hydroxy metabolites was removed and the compounds were re-extracted and analyzed by gas-liquid chromatography (GLC). Silylation of the extract was necessary in most cases for optimum GLC resolution of the alpha- and beta-hydroxy epimers. To demonstrate application of this method, the urine of guinea-pigs and rats which had received a single 40-mg dose of naloxone subcutaneously was analyzed. Analysis indicated a alpha/beta ratio of 0.41 for the guinea-pig. In contrast, the amount of 6-alpha-naloxol found in the urine of the rat was negligible in comparison with the 6-beta-hydroxy metabolite, indicating a species difference in the stereospecificity of the drug-metabolizing enzyme.
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Chapter 3: Narcotic Antagonists and Analgesics. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1976. [DOI: 10.1016/s0065-7743(08)61386-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Verebey K, Mulé SJ. Naltrexone pharmacology, pharmacokinetics, and metabolism: current status. THE AMERICAN JOURNAL OF DRUG AND ALCOHOL ABUSE 1975; 2:357-63. [PMID: 1227297 DOI: 10.3109/00952997509005661] [Citation(s) in RCA: 43] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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