1
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Benner JD, Cohen SM, Hollenbaugh JA, Fishman M. Fentanyl-induced respiratory depression in rodents is inhibited by bioabsorbable, subcutaneous naltrexone implants at 3.5 months. Addict Biol 2023; 28:e13350. [PMID: 38017645 DOI: 10.1111/adb.13350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/24/2023] [Accepted: 09/28/2023] [Indexed: 11/30/2023]
Abstract
The aim of this study is to determine if extended-release, bioabsorbable, subcutaneous naltrexone (NTX) implants inhibit respiratory depression after an IV injection of fentanyl. Bioabsorbable implants fabricated from two different release-controlling polymers, poly-D-L-lactide (PDLLA) and polycaprolactone (PCL), alone (placebo) or containing NTX, were subcutaneously implanted in Sprague Dawley rats. After 3.5 months of implantation, the rodents were administered an IV bolus of fentanyl through the tail vein. The placebo implant rats received a dose of 4 micrograms (mcg) - (10 mcg/kg/dose), while the NTX implanted animals received a dose of 8 mcg (20 mcg/kg/dose). The minimum active dose of fentanyl that caused a > 50 ± 2% depression in the respiration rate in the placebo implanted rodents was 4 mcg. The respiration rate of the placebo implanted rats dropped from 208 ± 14 breaths/minute at predose, to 84 ± 12 breaths/minute (p = 0.0003) at 2 min. In contrast, all NTX implanted animals easily tolerated twice the dose of 8 mcg of fentanyl without any significant reduction in respiration rate. The mean respiration rate = increased from 164 ± 22 breaths/minute at predose to 178 ± 17 breaths/minute (p = 0.24) at 2 min. The mean plasma concentrations of NTX, 3.5 months after implantation, ranged from 7.4 (±1.1) ng/mL to 80.3 (±37.5) ng/mL. Bioabsorbable implants containing NTX effectively blocked fentanyl-induced respiratory depression in rodents as compared with placebo implants, 3.5 months after implantation.
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Affiliation(s)
- Jeffrey D Benner
- The Drug Delivery Company, LLC dba Akyso, Salisbury, MD (JDB and SMC), LabCorp Drug Development Greenfield, IN (JAH), The Department of Psychiatry, Johns Hopkins School of Medicine and Maryland Treatment Centers, Baltimore, Maryland, USA
| | - Steven M Cohen
- The Drug Delivery Company, LLC dba Akyso, Salisbury, MD (JDB and SMC), LabCorp Drug Development Greenfield, IN (JAH), The Department of Psychiatry, Johns Hopkins School of Medicine and Maryland Treatment Centers, Baltimore, Maryland, USA
| | - Joseph A Hollenbaugh
- The Drug Delivery Company, LLC dba Akyso, Salisbury, MD (JDB and SMC), LabCorp Drug Development Greenfield, IN (JAH), The Department of Psychiatry, Johns Hopkins School of Medicine and Maryland Treatment Centers, Baltimore, Maryland, USA
| | - Marc Fishman
- The Drug Delivery Company, LLC dba Akyso, Salisbury, MD (JDB and SMC), LabCorp Drug Development Greenfield, IN (JAH), The Department of Psychiatry, Johns Hopkins School of Medicine and Maryland Treatment Centers, Baltimore, Maryland, USA
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2
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Essmat N, Karádi DÁ, Zádor F, Király K, Fürst S, Al-Khrasani M. Insights into the Current and Possible Future Use of Opioid Antagonists in Relation to Opioid-Induced Constipation and Dysbiosis. Molecules 2023; 28:7766. [PMID: 38067494 PMCID: PMC10708112 DOI: 10.3390/molecules28237766] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/21/2023] [Accepted: 11/22/2023] [Indexed: 12/18/2023] Open
Abstract
Opioid receptor agonists, particularly those that activate µ-opioid receptors (MORs), are essential analgesic agents for acute or chronic mild to severe pain treatment. However, their use has raised concerns including, among others, intestinal dysbiosis. In addition, growing data on constipation-evoked intestinal dysbiosis have been reported. Opioid-induced constipation (OIC) creates an obstacle to continuing treatment with opioid analgesics. When non-opioid therapies fail to overcome the OIC, opioid antagonists with peripheral, fast first-pass metabolism, and gastrointestinal localized effects remain the drug of choice for OIC, which are discussed here. At first glance, their use seems to only be restricted to constipation, however, recent data on OIC-related dysbiosis and its contribution to the appearance of several opioid side effects has garnered a great of attention from researchers. Peripheral MORs have also been considered as a future target for opioid analgesics with limited central side effects. The properties of MOR antagonists counteracting OIC, and with limited influence on central and possibly peripheral MOR-mediated antinociception, will be highlighted. A new concept is also proposed for developing gut-selective MOR antagonists to treat or restore OIC while keeping peripheral antinociception unaffected. The impact of opioid antagonists on OIC in relation to changes in the gut microbiome is included.
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Affiliation(s)
- Nariman Essmat
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad tér 4, H-1445 Budapest, Hungary; (N.E.); (D.Á.K.); (F.Z.); (K.K.); (S.F.)
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig 44519, Egypt
| | - Dávid Árpád Karádi
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad tér 4, H-1445 Budapest, Hungary; (N.E.); (D.Á.K.); (F.Z.); (K.K.); (S.F.)
| | - Ferenc Zádor
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad tér 4, H-1445 Budapest, Hungary; (N.E.); (D.Á.K.); (F.Z.); (K.K.); (S.F.)
| | - Kornél Király
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad tér 4, H-1445 Budapest, Hungary; (N.E.); (D.Á.K.); (F.Z.); (K.K.); (S.F.)
| | - Susanna Fürst
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad tér 4, H-1445 Budapest, Hungary; (N.E.); (D.Á.K.); (F.Z.); (K.K.); (S.F.)
| | - Mahmoud Al-Khrasani
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad tér 4, H-1445 Budapest, Hungary; (N.E.); (D.Á.K.); (F.Z.); (K.K.); (S.F.)
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3
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Jepkes S, Josee-Lemoy M, Knych H, de Lucena T, Ardeshir A, Stockinger DE. The Pharmacokinetics of Subcutaneous Methylnaltrexone Bromide in Rhesus Macaques ( Macaca mulatta). JOURNAL OF THE AMERICAN ASSOCIATION FOR LABORATORY ANIMAL SCIENCE : JAALAS 2023; 62:260-266. [PMID: 37080736 PMCID: PMC10230534 DOI: 10.30802/aalas-jaalas-22-000111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Revised: 01/13/2023] [Accepted: 01/23/2023] [Indexed: 04/22/2023]
Abstract
Opioids are an integral component of pain management for nonhuman primates. These potent analgesics also adverse gastrointestinal (GI) effects that include constipation, bloating, and delayed gastric emptying. Methylnaltrexone bromide (MNTX) is a selective, peripherally acting μ- and κ-opioid receptor antagonist that can be used to mitigate the GI effects associated with opioid administration. Unlike naltrexone, a similar drug in this class, MNTX possesses an N-methyl-quaternary amine group that prevents it from crossing the blood brain barrier. This blockage allows inhibition of peripheral GI opioid receptors without affecting opioid-mediated analgesia in the central nervous system. We conducted a pharmacokinetic analysis of MNTX in serum and CSF of 6 healthy juvenile male rhesus macaques after subcutaneous administration of a 0.15-mg/kg dose. We hypothesized that the macaques would demonstrate a Tmax of 0.5 h, similar to that of humans, and that no MNTX would be detected in the CSF. This treatment resulted in a peak serum concentration of 114 ± 44 ng/mL at 0.25 ± 0.00 h; peak CSF at concentrations were 0.34 ± 0.07 ng/mL at the Tmax. These data show that subcutaneous administration of MNTX to rhesus macaques may block peripheral adverse effects of opioids without interfering with their central analgesic effects.
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Affiliation(s)
- Sarah Jepkes
- Primate Medicine Services, California National Primate Research Center, University of California, Davis, California
| | - Marie Josee-Lemoy
- Primate Medicine Services, California National Primate Research Center, University of California, Davis, California
| | - Heather Knych
- California Animal Health and Food Safety Lab Molecular Biosciences, University of California, Davis, California
| | - Thiago de Lucena
- Division of Economics, San Diego State University, San Diego, California; and
| | - Amir Ardeshir
- Infectious Disease Unit, California National Primate Research Center, University of California, Davis, California
| | - Diane E Stockinger
- Primate Medicine Services, California National Primate Research Center, University of California, Davis, California
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4
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Huang B, Li M, Klongkumnuankarn P, Mendez RE, Gillespie JC, Stevens DL, Dewey WL, Selley DE, Zhang Y. Rational Design, Chemical Syntheses, and Biological Evaluations of Peripherally Selective Mu Opioid Receptor Ligands as Potential Opioid Induced Constipation Treatment. J Med Chem 2022; 65:4991-5003. [PMID: 35255683 PMCID: PMC10546485 DOI: 10.1021/acs.jmedchem.1c02185] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Opioid-induced constipation (OIC) is a common adverse effect of opioid analgesics. Peripherally acting μ opioid receptor antagonists (PAMORAs) can be applied in the treatment of OIC without compromising the analgesic effects. NAP, a 6β-N-4-pyridyl-substituted naltrexamine derivative, was previously identified as a potent and selective MOR antagonist mainly acting peripherally but with some CNS effects. Herein, we introduced a highly polar aromatic moiety, for example, a pyrazolyl or imidazolyl ring to decrease CNS MPO scores in order to reduce passive BBB permeability. Four compounds 2, 5, 17, and 19, when administered orally, were able to increase intestinal motility during morphine-induced constipation in the carmine red dye assays. Among them, compound 19 (p.o.) improved GI tract motility by 75% while orally administered NAP and methylnaltrexone showed no significant effects at the same dose. Thus, this compound seemed a promising agent to be further developed as an oral treatment for OIC.
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Affiliation(s)
- Boshi Huang
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, 800 East Leigh Street, Richmond, Virginia 23298, United States
| | - Mengchu Li
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, 800 East Leigh Street, Richmond, Virginia 23298, United States
| | - Pornprom Klongkumnuankarn
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, 800 East Leigh Street, Richmond, Virginia 23298, United States
| | - Rolando E Mendez
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, 410 North 12th Street, Richmond, Virginia 23298, United States
| | - James C Gillespie
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, 410 North 12th Street, Richmond, Virginia 23298, United States
| | - David L Stevens
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, 410 North 12th Street, Richmond, Virginia 23298, United States
| | - William L Dewey
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, 410 North 12th Street, Richmond, Virginia 23298, United States
| | - Dana E Selley
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, 410 North 12th Street, Richmond, Virginia 23298, United States
| | - Yan Zhang
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, 800 East Leigh Street, Richmond, Virginia 23298, United States
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5
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Atigari DV, Paton KF, Uprety R, Váradi A, Alder AF, Scouller B, Miller JH, Majumdar S, Kivell BM. The mixed kappa and delta opioid receptor agonist, MP1104, attenuates chemotherapy-induced neuropathic pain. Neuropharmacology 2021; 185:108445. [PMID: 33383089 PMCID: PMC8344368 DOI: 10.1016/j.neuropharm.2020.108445] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 11/20/2020] [Accepted: 12/20/2020] [Indexed: 01/04/2023]
Abstract
Effective treatments for chronic pain without abuse liability are urgently needed. One in 5 adults suffer chronic pain and half of these patients report inefficient treatment. Mu opioid receptor agonists (MOP), including oxycodone, tramadol and morphine, are often prescribed to treat chronic pain, however, use of drugs targeting MOP can lead to drug dependency, tolerance and overdose deaths. Kappa opioid receptor (KOP) agonists have antinociceptive effects without abuse potential; however, they have not been utilised clinically due to dysphoria and sedation. We hypothesise that mixed opioid receptor agonists targeting the KOP and delta opioid receptor (DOP) would have a wider therapeutic index, with the rewarding effects of DOP negating the negative effects of KOP. MP1104, an analogue of 3-Iodobenzoyl naltrexamine, is a novel mixed opioid receptor agonist with potent antinociceptive effects mediated via KOP and DOP in mice without rewarding or aversive effects. In this study, we show MP1104 has potent, long-acting antinociceptive effects in the warm-water tail-withdrawal assay in male and female mice and rats; and is longer acting than morphine. In the paclitaxel-induced neuropathic pain model in mice, MP1104 reduced both mechanical and cold allodynia and unlike morphine, did not produce tolerance when administered daily for 23 days. Moreover, MP1104 did not induce sedative effects in the open-field locomotor activity test, respiratory depression in mice using whole-body plethysmography, or have cross-tolerance with morphine. This data supports the therapeutic development of mixed opioid receptor agonists, particularly mixed KOP/DOP agonists, as non-addictive pain medications with reduced tolerance.
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Affiliation(s)
- Diana Vivian Atigari
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | - Kelly Frances Paton
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | - Rajendra Uprety
- Molecular Pharmacology Program and Department of Neurology, Memorial Sloan Kettering Cancer Centre, New York, USA
| | - András Váradi
- Molecular Pharmacology Program and Department of Neurology, Memorial Sloan Kettering Cancer Centre, New York, USA
| | - Amy Frances Alder
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | - Brittany Scouller
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | - John H Miller
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | - Susruta Majumdar
- Center of Clinical Pharmacology, St. Louis College of Pharmacy and Washington University School of Medicine, St. Louis, MO, USA
| | - Bronwyn Maree Kivell
- School of Biological Sciences, Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand.
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6
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Walentiny DM, Komla E, Moisa LT, Mustafa MA, Poklis JL, Akbarali HI, Beardsley PM. Methylnaltrexone crosses the blood-brain barrier and attenuates centrally-mediated behavioral effects of morphine and oxycodone in mice. Neuropharmacology 2020; 185:108437. [PMID: 33316279 DOI: 10.1016/j.neuropharm.2020.108437] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/27/2020] [Accepted: 12/04/2020] [Indexed: 11/18/2022]
Abstract
BACKGROUND Antagonism of peripheral opioid receptors by methylnaltrexone (MNTX) was recently proposed as a potential mechanism to attenuate the development of opioid analgesic tolerance based on experiments conducted in mice. However, reports indicate that MNTX is demethylated to naltrexone (NTX) in mice, and NTX may subsequently cross the blood-brain barrier to antagonize centrally-mediated opioid effects. The goal of this study was to determine whether MNTX alters centrally-mediated behaviors elicited by the opioid analgesics, morphine and oxycodone, and to quantify concentrations of MNTX and NTX in blood and brain following their administration in mice. METHODS Combinations of MNTX and morphine were tested under acute and chronic conditions in thermal nociceptive assays. Effects of MNTX and NTX pretreatment were assessed in an oxycodone discrimination operant procedure. Blood and brain concentrations of these antagonists were quantified after their administration using liquid chromatography-mass spectrometry. RESULTS MNTX dose-dependently attenuated acute and chronic morphine antinociception. MNTX and NTX dose-dependently antagonized the discriminative stimulus effects of oxycodone. MNTX and NTX were detected in both blood and brain after administration of MNTX, confirming its demethylation and demonstrating that MNTX itself can cross the blood-brain barrier. CONCLUSIONS These results provide converging behavioral and analytical evidence that MNTX administration in mice attenuates centrally-mediated effects produced by opioid analgesics and results in functional concentrations of MNTX and NTX in blood and brain. Collectively, these findings indicate that MNTX cannot be administered systemically in mice for making inferences that its effects are peripherally restricted.
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Affiliation(s)
- D Matthew Walentiny
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, 1217 E. Marshall Street, Richmond, VA, 23298-0613, USA.
| | - Essie Komla
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, 1217 E. Marshall Street, Richmond, VA, 23298-0613, USA
| | - Léa T Moisa
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, 1217 E. Marshall Street, Richmond, VA, 23298-0613, USA
| | - Mohammed A Mustafa
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, 1217 E. Marshall Street, Richmond, VA, 23298-0613, USA
| | - Justin L Poklis
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, 1217 E. Marshall Street, Richmond, VA, 23298-0613, USA
| | - Hamid I Akbarali
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, 1217 E. Marshall Street, Richmond, VA, 23298-0613, USA
| | - Patrick M Beardsley
- Department of Pharmacology & Toxicology, Virginia Commonwealth University, 1217 E. Marshall Street, Richmond, VA, 23298-0613, USA; Institute for Drug and Alcohol Studies & Center for Biomarker Research and Precision Medicine, Virginia Commonwealth University, 410 N. 12th Street, PO Box 980613, Richmond, VA, 23298-0613, USA
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7
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Blomqvist KJ, Dudek KA, Viisanen H, Mätlik K, Ahlström FHG, Laitila J, Kalso EA, Rauhala PV, Lilius TO. Antagonism of peripheral opioid receptors by methylnaltrexone does not prevent morphine tolerance in rats. J Neurosci Res 2020; 100:329-338. [PMID: 32459013 DOI: 10.1002/jnr.24638] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/16/2020] [Accepted: 04/20/2020] [Indexed: 11/10/2022]
Abstract
Opioids are effective analgesics in the management of severe pain. However, tolerance, leading to dose escalation and adverse effects are significant limiting factors in their use. The role of peripheral opioid receptors in analgesia has been discussed especially under inflammatory conditions. The results from pharmacological and conditional knockout studies together do not provide a clear picture of the contribution of peripheral opioid receptors on antinociceptive tolerance and this needs to be evaluated. Therefore, we studied whether the peripherally restricted opioid receptor antagonist, methylnaltrexone (MNTX), could prevent morphine tolerance without attenuating the antinociceptive effect of morphine. Male Sprague-Dawley rats were treated for 7 days with increasing subcutaneous doses of morphine (5-30 mg/kg) and were coadministered saline, MNTX (0.5 or 2 mg/kg), or naltrexone (NTX; 2 mg/kg). Nociception was assessed with tail-flick, hotplate, and von Frey tests. Morphine, MNTX, and NTX concentrations in the plasma, brain, and spinal cord were measured by liquid chromatography-tandem mass spectrometry. In acute coadministration, NTX, but not MNTX, abolished the acute antinociceptive effects of morphine in all nociceptive tests. The antinociceptive tolerance after repeated morphine administration was also prevented by NTX but not by MNTX. MNTX penetrated to the spinal cord and the brain to some extent after repeated administration. The results do not support the use of MNTX for preventing opioid tolerance and also suggest that morphine tolerance is mediated by central rather than peripheral opioid receptors in the rat.
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Affiliation(s)
- Kim Juhani Blomqvist
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Katarzyna Anna Dudek
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Hanna Viisanen
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Kert Mätlik
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Fredrik Harry Gustav Ahlström
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jouko Laitila
- Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Department of Clinical Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki University Hospital, Finland
| | - Eija Anneli Kalso
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Department of Anaesthesiology, Intensive Care Medicine, and Pain Medicine, University of Helsinki, Helsinki University Hospital, Helsinki, Finland
| | - Pekka Veli Rauhala
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Tuomas Olavi Lilius
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Department of Clinical Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki University Hospital, Finland.,Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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8
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Komla E, Stevens DL, Zheng Y, Zhang Y, Dewey WL, Akbarali HI. Experimental Colitis Enhances the Rate of Antinociceptive Tolerance to Morphine via Peripheral Opioid Receptors. J Pharmacol Exp Ther 2019; 370:504-513. [PMID: 31248978 PMCID: PMC6806632 DOI: 10.1124/jpet.119.256941] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 06/24/2019] [Indexed: 01/21/2023] Open
Abstract
Opioids are highly effective analgesics, however, their therapeutic use is limited by adverse effects that include respiratory depression, dependence, and tolerance. Inflammation has been implicated as a significant driver for the development of tolerance to opioids. Recent studies show that chronic morphine in mice results in gut microbial dysbiosis and inflammation in the colon. In the present study, we examined whether colonic inflammation results in tolerance to the antinociceptive effects of morphine. Colonic inflammation was induced in mice by intrarectal administration of 2,4,6-trinitro-benzene sulfonic acid. The development of antinociceptive tolerance was determined by warm-water tail-immersion assay in mice implanted with 25-, 50-, or 75-mg morphine pellet. Colonic inflammation significantly enhanced the rate at which tolerance developed in each cohort of chronic morphine-treated mice. At the lowest dose of morphine pellet (25 mg), antinociceptive tolerance only developed in the presence of colonic inflammation, whereas in 50- and 75-mg pelleted mice, tolerance developed faster in the inflamed animals than in the noninflamed mice. The enhanced antinociceptive tolerance was attenuated with daily administration of peripheral opioid receptor antagonist, 6β-N-heterocyclic-substituted naltrexamine derivative [17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6β-[(4'pyridyl)acetamido]morphinan (NAP)], irrespective of colonic inflammation. Collectively, these findings show that the rate of tolerance to morphine antinociception is exaggerated in the presence of colonic inflammation, and tolerance is prevented by a peripheral μ-opioid receptor antagonist. These studies suggest a peripheral component to the development of antinociceptive tolerance to opioids. Furthermore, peripherally selective opioid antagonists may be useful adjuncts in opioid-based pain management. SIGNIFICANCE STATEMENT: This study supports the notion that inflammation influences the development of antinociceptive tolerance to chronic morphine exposure. We found that, in the presence of colonic inflammation, the rate of development of tolerance to the antinociceptive effects of morphine increased. We also found that treatment with a peripheral opioid receptor antagonist prevented morphine antinociceptive tolerance. Increasing opioid intake during an inflammatory state would result in decreased analgesia and enhanced analgesic tolerance, which puts patients with inflammatory bowel diseases, inflammatory joint diseases, and sickle cell anemia at risk for heavy opioid use.
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Affiliation(s)
- Essie Komla
- Departments of Pharmacology and Toxicology (E.K., D.L.S., W.L.D., H.I.A.) and Medicinal Chemistry (Y.Zhe., Y.Zha.), Virginia Commonwealth University, Richmond, Virginia
| | - David L Stevens
- Departments of Pharmacology and Toxicology (E.K., D.L.S., W.L.D., H.I.A.) and Medicinal Chemistry (Y.Zhe., Y.Zha.), Virginia Commonwealth University, Richmond, Virginia
| | - Yi Zheng
- Departments of Pharmacology and Toxicology (E.K., D.L.S., W.L.D., H.I.A.) and Medicinal Chemistry (Y.Zhe., Y.Zha.), Virginia Commonwealth University, Richmond, Virginia
| | - Yan Zhang
- Departments of Pharmacology and Toxicology (E.K., D.L.S., W.L.D., H.I.A.) and Medicinal Chemistry (Y.Zhe., Y.Zha.), Virginia Commonwealth University, Richmond, Virginia
| | - William L Dewey
- Departments of Pharmacology and Toxicology (E.K., D.L.S., W.L.D., H.I.A.) and Medicinal Chemistry (Y.Zhe., Y.Zha.), Virginia Commonwealth University, Richmond, Virginia
| | - Hamid I Akbarali
- Departments of Pharmacology and Toxicology (E.K., D.L.S., W.L.D., H.I.A.) and Medicinal Chemistry (Y.Zhe., Y.Zha.), Virginia Commonwealth University, Richmond, Virginia
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9
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Raffa RB, Taylor R, Pergolizzi JV. Treating opioid‐induced constipation in patients taking other medications: Avoiding CYP450 drug interactions. J Clin Pharm Ther 2019; 44:361-371. [DOI: 10.1111/jcpt.12812] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/15/2019] [Accepted: 01/18/2019] [Indexed: 02/06/2023]
Affiliation(s)
- Robert B. Raffa
- University of Arizona College of Pharmacy Tucson Arizona
- Temple University School of Pharmacy Philadelphia Pennsylvania
- Neumentum Inc Palo Alto California
- The NEMA Research Group Naples Florida
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10
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Mozaffari S, Nikfar S, Abdollahi M. Methylnaltrexone bromide for the treatment of opioid-induced constipation. Expert Opin Pharmacother 2018; 19:1127-1135. [DOI: 10.1080/14656566.2018.1491549] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Shilan Mozaffari
- Division of Pharmaceutical and Narcotic Affaire, Vice Chancellor for Food and Drug, Kurdistan University of Medical Sciences, Sanandaj, Iran
| | - Shekoufeh Nikfar
- Department of Pharmacoeconomics and Pharmaceutical Administration, Faculty of Pharmacy and Pharmaceutical Policy Research Center, Tehran University of Medical Sciences, Tehran, Iran
- The Institute of Pharmaceutical Sciences (TIPS), Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Abdollahi
- The Institute of Pharmaceutical Sciences (TIPS), Tehran University of Medical Sciences, Tehran, Iran
- Department of Toxicology and Pharmacology, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
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Sobolevsky T, Kucherova Y, Ahrens B. Identification of oxymorphone as decomposition product of the permitted drug methylnaltrexone. Drug Test Anal 2018; 10:892-895. [DOI: 10.1002/dta.2353] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/13/2017] [Accepted: 12/14/2017] [Indexed: 11/08/2022]
Affiliation(s)
- T. Sobolevsky
- UCLA Olympic Analytical Laboratory, Department of Pathology & Laboratory Medicine; Geffen School of Medicine; Los Angeles California USA
| | - Y. Kucherova
- UCLA Olympic Analytical Laboratory, Department of Pathology & Laboratory Medicine; Geffen School of Medicine; Los Angeles California USA
| | - B. Ahrens
- UCLA Olympic Analytical Laboratory, Department of Pathology & Laboratory Medicine; Geffen School of Medicine; Los Angeles California USA
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Drinovac Vlah V, Filipović B, Bach-Rojecky L, Lacković Z. Role of central versus peripheral opioid system in antinociceptive and anti-inflammatory effect of botulinum toxin type A in trigeminal region. Eur J Pain 2017; 22:583-591. [PMID: 29134730 DOI: 10.1002/ejp.1146] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/12/2017] [Indexed: 12/12/2022]
Abstract
BACKGROUND Although botulinum toxin type A (BT-A) is approved for chronic migraine treatment, its site and mechanism of action are still elusive. Recently our group discovered that suppression of CGRP release from dural nerve endings might account for antimigraine action of pericranially injected BT-A. We demonstrated that central antinociceptive effect of BT-A in sciatic region involves endogenous opioid system as well. Here we investigated possible interaction of BT-A with endogenous opioid system within the trigeminal region. METHODS In orofacial formalin test we investigated the influence of centrally acting opioid antagonist naltrexone (2 mg/kg, s.c.) versus peripherally acting methylnaltrexone (2 mg/kg, s.c.) on BT-A's (5 U/kg, s.c. into whisker pad) or morphine's (6 mg/kg, s.c.) antinociceptive effect and the effect on dural neurogenic inflammation (DNI). DNI was assessed by Evans blue-plasma protein extravasation. RESULTS Naltrexone abolished the effect of BT-A on pain and dural plasma protein extravasation, whereas peripherally acting methylnaltrexone did not change either BT-A's effect on pain or its effect on dural extravasation. Naltrexone abolished the antinociceptive and anti-inflammatory effects of morphine, as well. However, methylnaltrexone decreased the antinociceptive effect of morphine only partially in the second phase of the test and had no significant effect on morphine-mediated reduction in DNI. CONCLUSIONS Morphine acts on pain in trigeminal region both peripherally and centrally, whereas the effect on dural plasma protein extravasation seems to be only centrally mediated. However, the interaction of BT-A with endogenous opioid system, with consequent inhibition of nociceptive transmission as well as the DNI, occurs primarily centrally. SIGNIFICANCE Botulinum toxin type A (BT-A)'s axonal transport and potential transcytosis suggest that its antinociceptive effect might involve diverse neurotransmitters at different sites of trigeminal system. Here we discovered that the reduction in pain and accompanying DNI involves the interaction of BT-A with central endogenous opioid system (probably at the level of trigeminal nucleus caudalis).
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Affiliation(s)
- V Drinovac Vlah
- Department of Pharmacology, University of Zagreb Faculty of Pharmacy and Biochemistry, Croatia
| | - B Filipović
- Laboratory of Molecular Neuropharmacology, Department of Pharmacology, University of Zagreb School of Medicine, Croatia.,Department of Otorhinolaryngology & Head and Neck Surgery, University Hospital Sveti Duh, Zagreb, Croatia
| | - L Bach-Rojecky
- Department of Pharmacology, University of Zagreb Faculty of Pharmacy and Biochemistry, Croatia
| | - Z Lacković
- Laboratory of Molecular Neuropharmacology, Department of Pharmacology, University of Zagreb School of Medicine, Croatia
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Zhang D, Ma JY, Yang M, Deng M, Liu H. Pharmacokinetic study of methylnaltrexone after single and multiple subcutaneous administrations in healthy Chinese subjects. Xenobiotica 2017; 48:804-808. [PMID: 28776489 DOI: 10.1080/00498254.2017.1364449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Dan Zhang
- Department of Clinical Pharmacology, Aerospace Center Hospital, Beijing, China
| | - Jing-Yi Ma
- Department of Clinical Pharmacology, Aerospace Center Hospital, Beijing, China
| | - Man Yang
- Department of Clinical Pharmacology, Aerospace Center Hospital, Beijing, China
| | - Ming Deng
- Department of Clinical Pharmacology, Aerospace Center Hospital, Beijing, China
| | - Huichen Liu
- Department of Clinical Pharmacology, Aerospace Center Hospital, Beijing, China
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14
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Leppert W. Emerging therapies for patients with symptoms of opioid-induced bowel dysfunction. DRUG DESIGN DEVELOPMENT AND THERAPY 2015; 9:2215-31. [PMID: 25931815 PMCID: PMC4404965 DOI: 10.2147/dddt.s32684] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Opioid-induced bowel dysfunction (OIBD) comprises gastrointestinal (GI) symptoms, including dry mouth, nausea, vomiting, gastric stasis, bloating, abdominal pain, and opioid-induced constipation, which significantly impair patients’ quality of life and may lead to undertreatment of pain. Traditional laxatives are often prescribed for OIBD symptoms, although they display limited efficacy and exert adverse effects. Other strategies include prokinetics and change of opioids or their administration route. However, these approaches do not address underlying causes of OIBD associated with opioid effects on mostly peripheral opioid receptors located in the GI tract. Targeted management of OIBD comprises purely peripherally acting opioid receptor antagonists and a combination of opioid receptor agonist and antagonist. Methylnaltrexone induces laxation in 50%–60% of patients with advanced diseases and OIBD who do not respond to traditional oral laxatives without inducing opioid withdrawal symptoms with similar response (45%–50%) after an oral administration of naloxegol. A combination of prolonged-release oxycodone with prolonged-release naloxone (OXN) in one tablet (a ratio of 2:1) provides analgesia with limited negative effect on the bowel function, as oxycodone displays high oral bioavailability and naloxone demonstrates local antagonist effect on opioid receptors in the GI tract and is totally inactivated in the liver. OXN in daily doses of up to 80 mg/40 mg provides equally effective analgesia with improved bowel function compared to oxycodone administered alone in patients with chronic non-malignant and cancer-related pain. OIBD is a common complication of long-term opioid therapy and may lead to quality of life deterioration and undertreatment of pain. Thus, a complex assessment and management that addresses underlying causes and patomechanisms of OIBD is recommended. Newer strategies comprise methylnaltrexone or OXN administration in the management of OIBD, and OXN may be also considered as a preventive measure of OIBD development in patients who require opioid administration.
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Affiliation(s)
- Wojciech Leppert
- Chair and Department of Palliative Medicine, Poznan University of Medical Sciences, Poznan, Poland
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16
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Tang C, Tang C, Zhan W, Du J, Wang Z, Peng X. Strategies for ascertaining the interference of phase II metabolites co-eluting with parent compounds using LC-MS/MS. J Sep Sci 2013; 36:2584-92. [PMID: 23868670 DOI: 10.1002/jssc.201300235] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 05/05/2013] [Accepted: 05/29/2013] [Indexed: 11/10/2022]
Abstract
LC-MS/MS is currently the most selective and efficient tool for the quantitative analysis of drugs and metabolites in the pharmaceutical industry and in clinical assays. However, phase II metabolites sometimes negatively affect the selectivity and efficiency of the LC-MS/MS method, especially for the metabolites that possess similar physicochemical characteristics and generate the same precursor ions as their parent compounds due to the in-source collision-induced dissociation during the ionization process. This paper proposes some strategies for examining co-eluting metabolites existing in real samples, and further assuring whether these metabolites could affect the selectivity and accuracy of the analytical methods. Strategies using precursor-ion scans and product-ion scans were applied in this study. An example drug, namely, caffeic acid phenethyl ester, which can generate many endogenous phase II metabolites, was selected to conduct this work. These metabolites, generated during the in vivo metabolic processes, can be in-source-dissociated to the precursor ions of their parent compounds. If these metabolites are not separated from their parent compounds, the quantification of the target analytes (parent compounds) would be influenced. Some metabolites were eluted closely to caffeic acid phenethyl ester on LC columns, although long columns and relatively long elution programs were used. The strategies can be utilized in quantitative methodologies that apply LC-MS/MS to assure the performance of selectivity, thus enhancing the reliability of the experimental data.
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Affiliation(s)
- Caiming Tang
- State key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China.
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17
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Bader S, Dürk T, Becker G. Methylnaltrexone for the treatment of opioid-induced constipation. Expert Rev Gastroenterol Hepatol 2013; 7:13-26. [PMID: 23265145 DOI: 10.1586/egh.12.63] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Opioids are the drugs of choice for treating moderate-to-severe pain, especially for patients in the end stage of cancer or other advanced illnesses, and also in critical care or for the treatment of chronic pain. Side effects such as nausea, pruritus, dizziness and constipation have to be controlled in order to use these drugs to their full potential. Opioid-induced bowel syndrome and constipation caused by activation of μ-receptors in the gut can have such distressing effects that some patients prefer to forego adequate pain control. Methylnaltrexone is a μ-opioid receptor antagonist that, unlike naltrexone or naloxone, does not pass the blood-brain barrier, and therefore does not impair the centrally mediated analgesic effect of opioids. It is licensed for the treatment of opioid-induced constipation in palliative care in more than 50 countries. This article presents practically relevant pharmacological data, basic research results and evidence from clinical research about methylnaltrexone, and outlines potential future therapeutic options for this promising drug.
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Affiliation(s)
- Sabine Bader
- Department of Palliative Care, University Medical Center Freiburg, Robert-Koch-Str. 3, D-79106 Freiburg, Germany.
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Oswald S, Schumacher G, Siegmund W. Quantitative determination of methylnaltrexone in human serum using liquid chromatography-tandem mass spectrometry. J Pharm Biomed Anal 2011; 56:1079-84. [PMID: 21880450 DOI: 10.1016/j.jpba.2011.08.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 08/04/2011] [Accepted: 08/05/2011] [Indexed: 11/15/2022]
Abstract
Methylnaltrexone (MNTX) is a novel peripherally acting μ-opioid antagonist that prevents peripheral side effects of opioid drugs such as constipation without affecting the analgesia. We developed a selective and sensitive assay to measure MTNX concentrations in human serum. The drug was measured after protein precipitation with perchloric acid using naltrexone as internal standard and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for detection. The chromatography was performed isocratically on a RP18 column using 25 mM ammonium acetate buffer (pH 4)/acetonitrile (90%/10%; flow rate 200 μl/min) as mobile phase. The MS/MS analysis was performed in positive ionization mode monitoring the m/z transitions 356.4/284.2 for MNTX and 342.4/324.2 for naltrexone. The method was validated according to selectivity, linearity, accuracy, precision, recovery, matrix effects and stability. The validation range for MNTX in serum was 0.5-250 ng/ml. The developed LC-MS/MS was shown to be valid and successfully applied to measure serum-concentration-time curves of MNTX in a pilot study in healthy volunteers.
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Affiliation(s)
- Stefan Oswald
- Department of Clinical Pharmacology, Ernst-Moritz-Arndt University Greifswald, Friedrich-Loeffler-Str. 23d, 17487 Greifswald, Germany.
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Rotshteyn Y, Boyd TA, Yuan CS. Methylnaltrexone bromide: research update of pharmacokinetics following parenteral administration. Expert Opin Drug Metab Toxicol 2011; 7:227-35. [DOI: 10.1517/17425255.2011.549824] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Opioid antagonists for prevention and treatment of opioid-induced gastrointestinal effects. Curr Opin Anaesthesiol 2010; 23:616-22. [PMID: 20543677 DOI: 10.1097/aco.0b013e32833c3473] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE OF REVIEW The therapeutic action of opioid analgesics is compromised by peripheral adverse effects, among which constipation is the most disabling as laxatives often fail to provide satisfactory relief. This review highlights recent advances in the specific control of opioid-induced constipation by opioid receptor antagonists with limited systemic bioavailability or a peripherally restricted site of action. RECENT FINDINGS The specific management of opioid-induced bowel dysfunction is currently based on three drug entities: oral alvimopan for the shortening of postoperative ileus associated with opioid-induced pain control after bowel resection, subcutaneous methylnaltrexone for the reduction of opioid-induced constipation in patients with advanced illness, and a fixed combination of oral prolonged-release naloxone with prolonged-release oxycodone for the treatment of noncancer and cancer pain. All three drug entities have been shown to attenuate opioid-induced motor stasis in the gut with a favorable adverse effect profile, while the analgesic effect of opioids remains unabated. SUMMARY The availability of opioid receptor antagonists with restricted access to the central nervous system provides a novel opportunity to specifically control opioid-induced constipation and other peripheral adverse effects of opioid analgesics. Further studies are needed to evaluate the long-term efficacy, safety and cost-effectiveness of this approach.
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Current world literature. Neuroanaesthesia. Pain medicine. Regional anaesthesia. Curr Opin Anaesthesiol 2010; 23:671-8. [PMID: 20811177 DOI: 10.1097/aco.0b013e32833f3f68] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Tong Z, Chandrasekaran A, Li H, Rotshteyn Y, Erve JCL, Demaio W, Talaat R, Hultin T, Scatina J. In vitro metabolism and identification of human enzymes involved in the metabolism of methylnaltrexone. Drug Metab Dispos 2010; 38:801-7. [PMID: 20173089 DOI: 10.1124/dmd.110.032169] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Methylnaltrexone (MNTX) is a peripherally acting mu-opioid receptor antagonist and is currently indicated for the treatment of opioid-induced constipation in patients with advanced illness who are receiving palliative care, when response to laxative therapy has not been sufficient. Sulfation to MNTX-3-sulfate (M2) and carbonyl reduction to methyl-6alpha-naltrexol (M4) and methyl-6beta-naltrexol (M5) are the primary metabolic pathways for MNTX in humans. The objectives of this study were to investigate MNTX in vitro metabolism in human and nonclinical species and to identify the human enzymes involved in MNTX metabolism. Of the five commercially available sulfotransferases investigated, only SULT2A1 and SULT1E1 catalyzed M2 formation. Formation of M4 and M5 was catalyzed by NADPH-dependent hepatic cytosolic enzymes, which were identified using selective chemical inhibitors (10 and 100 microM) for aldo-keto reductase (AKR) isoforms, short-chain dehydrogenase/reductase including carbonyl reductase, alcohol dehydrogenase, and quinone oxidoreductase. The results were then compared with the effects of the same inhibitors on 6beta-naltrexol formation from naltrexone, a structural analog of MNTX, which is catalyzed mainly by AKR1C4. The AKR1C inhibitor phenolphthalein inhibited MNTX and naltrexone reduction up to 98%. 5beta-Cholanic acid 3alpha,7alpha-diol, the AKR1C2 inhibitor, and medroxyprogesterone acetate, an inhibitor of AKR1C1, AKR1C2, and AKR1C4, inhibited MNTX reduction up to 67%. Other inhibitors were less potent. In conclusion, the carbonyl reduction of MNTX to M4 and M5 in hepatic cytosol was consistent with previous in vivo observations. AKR1C4 appeared to play a major role in the carbonyl reduction of MNTX, although multiple enzymes in the AKR1C subfamily may be involved. Human SULT2A1 and SULT1E1 were involved in MNTX sulfation.
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Affiliation(s)
- Zeen Tong
- Pfizer Inc., Collegeville, PA 19426, USA
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