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In Vitro and In Vivo Pharmaco-Toxicological Characterization of 1-Cyclohexyl-x-methoxybenzene Derivatives in Mice: Comparison with Tramadol and PCP. Int J Mol Sci 2021; 22:ijms22147659. [PMID: 34299276 PMCID: PMC8306156 DOI: 10.3390/ijms22147659] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/02/2021] [Accepted: 07/15/2021] [Indexed: 11/17/2022] Open
Abstract
1-cyclohexyl-x-methoxybenzene is a novel psychoactive substance (NPS), first discovered in Europe in 2012 as unknown racemic mixture of its three stereoisomers: ortho, meta and para. Each of these has structural similarities with the analgesic tramadol and the dissociative anesthetic phencyclidine. In light of these structural analogies, and based on the fact that both tramadol and phencyclidine are substances that cause toxic effects in humans, the aim of this study was to investigate the in vitro and in vivo pharmacodynamic profile of these molecules, and to compare them with those caused by tramadol and phencyclidine. In vitro studies demonstrated that tramadol, ortho, meta and para were inactive at mu, kappa and delta opioid receptors. Systemic administration of the three stereoisomers impairs sensorimotor responses, modulates spontaneous motor activity, induces modest analgesia, and alters thermoregulation and cardiorespiratory responses in the mouse in some cases, with a similar profile to that of tramadol and phencyclidine. Naloxone partially prevents only the visual sensorimotor impairments caused by three stereoisomers, without preventing other effects. The present data show that 1-cyclohexyl-x-methoxybenzene derivatives cause pharmaco-toxicological effects by activating both opioid and non-opioid mechanisms and suggest that their use could potentially lead to abuse and bodily harm.
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Abstract
Abstract
Aims
As an analgesic that acts upon the central nervous system (CNS), tramadol has gained popularity in treating moderate to severe pain. Recently, it has been increasingly reported as a drug of misuse with intentional overdoses or intoxications. This review focuses on tramadol intoxication in humans and its effects on different systems.
Subject and method
This narrative review provides a comprehensive view of the pharmacokinetics, mechanism of action, and incidence of tramadol toxicity with an in-depth look at its side effects. In addition, the main approaches to the management of tramadol poisoning are described.
Results
Tramadol poisoning can affect multiple organ systems: gastrointestinal, central nervous system (seizure, CNS depression, low-grade coma, anxiety, and over time anoxic brain damage), cardiovascular system (palpitation, mild hypertension to life-threatening complications such as cardiopulmonary arrest), respiratory system, renal system (renal failure with higher doses of tramadol intoxication), musculoskeletal system (rhabdomyolysis), endocrine system (hypoglycemia), as well as, cause serotonin syndrome. Seizure, a serious nervous disturbance, is more common in tramadol intoxication than with other opioids. Fatal tramadol intoxications are uncommon, except in ingestion cases concurrent with other medications, particularly CNS depressants, most commonly benzodiazepines, and ethanol.
Conclusion
With the increasing popularity of tramadol, physicians must be aware of its adverse effects, substantial abuse potential, and drug interactions, to weigh its risk–benefit ratio for pain management. Alternative therapies might be considered in patients with a previous overdose history to reduce risks for adverse outcomes.
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Ahmadimanesh M, Shadnia S, Rouini MR, Sheikholeslami B, Ahsani Nasab S, Ghazi-Khansari M. Correlation between plasma concentrations of tramadol and its metabolites and the incidence of seizure in tramadol-intoxicated patients. Drug Metab Pers Ther 2018; 33:75-83. [PMID: 29727299 DOI: 10.1515/dmpt-2017-0040] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 02/12/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Seizure is one of the important symptoms of tramadol poisoning, but its causes are still unknown. The aim of this study is to find a relationship between tramadol and the concentrations of its metabolites versus the incidence of seizures following the consumption of high doses of tramadol. METHODS For this purpose, the blood samples of 120 tramadol-intoxicated patients were collected. The patients were divided in two groups (seizure and non-seizure). The concentrations of tramadol and its metabolites (M1, M2 and M5) were measured by using a high-performance liquid chromatography method. The relationship between tramadol and the levels of its metabolites and seizure incidences was also investigated. RESULTS In 72% of the patients, seizures occurred in the first 3 h after the ingestion of tramadol. The seizure incidences were significantly correlated with the patients' gender, concentrations of tramadol, M1 and M2 and the history of previous seizures (p<0.001). The average concentration of M2 was significantly higher in males (p=0.003). A previous history of the use of sedative-hypnotics and the co-ingestion of benzodiazepines and other opioids were shown to significantly decrease the rate of seizure. The rate of seizure was directly related to the concentrations of tramadol and its metabolites. Higher M2 concentration in males can be considered a reason for increased incidences of seizures in males. The plasma concentration of M1 affected the onset of seizure. CONCLUSIONS Therefore, it can be concluded that differences in the levels of the metabolites can affect the threshold of seizure in tramadol-intoxicated patients.
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Affiliation(s)
- Mahnaz Ahmadimanesh
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
- Biopharmaceutics and Pharmacokinetic Division, Department of Pharmaceutics, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | - Shahin Shadnia
- Department of Clinical Toxicology, Loghman-Hakim Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Excellent Center of Clinical Toxicology, Ministry of Health and Medical Education, Tehran, Iran
| | - Mohammad Reza Rouini
- Biopharmaceutics and Pharmacokinetic Division, Department of Pharmaceutics, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Sara Ahsani Nasab
- Epidemiology and Biostatistics Department, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Mahmoud Ghazi-Khansari
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, P.O. Box 1416753955, Tehran, Iran, Tel/Fax: +9821-6640-2569, E-mail:
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Mahmoud MF, Gamal S, Shaheen MA, El-Fayoumi HM. The effects of tramadol on hepatic ischemia/reperfusion injury in rats. Indian J Pharmacol 2017; 48:275-80. [PMID: 27298497 PMCID: PMC4900000 DOI: 10.4103/0253-7613.182882] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Objectives: Tramadol is a centrally acting synthetic analgesic. It has a cardioprotective effect against myocardial ischemia-reperfusion (I/R) injury in isolated rat heart. We hypothesized that tramadol may exert a similar protective effect on hepatic I/R injury. Hence, the current investigation was designed to study the possible protective effects of tramadol on experimentally-induced hepatic I/R injury in rats. Materials and Methods: Tramadol was administered 30 min before ischemia following which the rats were subjected to 45 min of ischemia followed by 1 h of reperfusion. Results: Tramadol attenuated hepatic injury induced by I/R as evidenced by the reduction of transaminases, structural changes, and apoptotic cell death. It decreased the level of inflammatory markers such as tumor necrosis factor-alpha (TNF-α), TNF-α/interleukin-10 (IL-10) ratio, and nuclear factor-κB gene expression. It also increased the anti-inflammatory cytokine, IL-10 levels in hepatic tissues. Furthermore, it reduced oxidative stress parameters except manganese superoxide dismutase activity. Conclusion: The results suggest that tramadol has hepatoprotective effects against hepatic I/R injury via anti-inflammatory, antiapoptotic, and antioxidant effects.
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Affiliation(s)
- Mona F Mahmoud
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Samar Gamal
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Mohamed A Shaheen
- Department of Histology and Cell Biology, Faculty of Medicine, Zagazig University, Zagazig, Egypt
| | - Hassan M El-Fayoumi
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
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Tverdohleb T, Dinc B, Knezevic I, Candido KD, Knezevic NN. The role of cytochrome P450 pharmacogenomics in chronic non-cancer pain patients. Expert Opin Drug Metab Toxicol 2016; 12:1303-1311. [PMID: 27388970 DOI: 10.1080/17425255.2016.1209482] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
INTRODUCTION Pharmacogenomics is the field that studies an individualized treatment approach for patients' medication regimen that can impact drug safety, productivity, and personalized health care. Pharmacogenomics characterizes the genetic differences in metabolic pathways which can affect a patient's individual responses to drug treatments. Areas covered: The various responses to pharmacological agents are mainly determined by the different types of genetic variants of the CYP450. CYP2D6 polymorphism is well known for its variation in the metabolism of drugs from many therapeutic arenas, including some analgesic drugs such as codeine, hydromorphone, oxycodone and tramadol. Allele combinations determine the phenotypic expression, characterized as either: extensive metabolizer, intermediate metabolizer, ultra-rapid metabolizer and poor metabolizer. Expert opinion: The Human Genome Project (HGP) revolutionized the future of medicine and the way health care providers approach individualized patient treatment, and chronic pain management is one of those areas. The key findings in the literature appear to be related to the CYP2D6 expression and its high polymorphism influencing the metabolism of opioid medications, and the impact of that on the patient's therapeutic outcome thus exemplifying the importance of genetic testing for CYP2D6 in the process of physician therapeutic decision making.
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Affiliation(s)
- Tatiana Tverdohleb
- a Department of Anesthesiology , Advocate Illinois Masonic Medical Center , Chicago , IL , USA
| | - Bora Dinc
- a Department of Anesthesiology , Advocate Illinois Masonic Medical Center , Chicago , IL , USA
| | - Ivana Knezevic
- a Department of Anesthesiology , Advocate Illinois Masonic Medical Center , Chicago , IL , USA
| | - Kenneth D Candido
- a Department of Anesthesiology , Advocate Illinois Masonic Medical Center , Chicago , IL , USA.,b Department of Anesthesiology, College of Medicine , University of Illinois , Chicago , IL , USA.,c Department of Surgery, College of Medicine , University of Illinois , Chicago , IL , USA
| | - Nebojsa Nick Knezevic
- a Department of Anesthesiology , Advocate Illinois Masonic Medical Center , Chicago , IL , USA.,b Department of Anesthesiology, College of Medicine , University of Illinois , Chicago , IL , USA.,c Department of Surgery, College of Medicine , University of Illinois , Chicago , IL , USA
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Aguirre JA, Lucchinetti E, Clanachan AS, Plane F, Zaugg M. Unraveling Interactions Between Anesthetics and the Endothelium. Anesth Analg 2016; 122:330-48. [DOI: 10.1213/ane.0000000000001053] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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de Fátima Leão V, Raimundo JM, Ferreira LLDM, Santos-Silva JC, Vettorazzi JF, Bonfleur ML, Carneiro EM, Ribeiro RA. Effects of Paternal Hypothalamic Obesity and Taurine Supplementation on Adiposity and Vascular Reactivity in Rat Offspring. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 803:749-63. [DOI: 10.1007/978-3-319-15126-7_60] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Aboul-Enein MN, El-Azzouny AA, Maklad YA, Ismail MA, Ismail NSM, Hassan RM. Design and synthesis of certain substituted cycloalkanecarboxamides structurally related to safinamide with anticonvulsant potential. RESEARCH ON CHEMICAL INTERMEDIATES 2013. [DOI: 10.1007/s11164-013-1488-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Side-effects of analgesic kyotorphin derivatives: advantages over clinical opioid drugs. Amino Acids 2013; 45:171-8. [PMID: 23471674 DOI: 10.1007/s00726-013-1484-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 02/23/2013] [Indexed: 01/23/2023]
Abstract
The adverse side-effects associated with opioid administration restrain their use as analgesic drugs and call for new solutions to treat pain. Two kyotorphin derivatives, kyotorphin-amide (KTP-NH₂) and ibuprofen-KTP-NH₂ (IbKTP-NH₂) are promising alternatives to opioids: they trigger analgesia via an indirect opioid mechanism and are highly effective in several pain models following systemic delivery. In vivo side-effects of KTP-NH₂ and IbKTP-NH₂ are, however, unknown and were evaluated in the present study using male adult Wistar rats. For comparison purposes, morphine and tramadol, two clinically relevant opioids, were also studied. Results showed that KTP-derivatives do not cause constipation after systemic administration, in contrast to morphine. Also, no alterations were observed in blood pressure or in food and water intake, which were only affected by tramadol. A reduction in micturition was detected after KTP-NH₂ or tramadol administrations. A moderate locomotion decline was detected after IbKTP-NH₂-treatment. The side-effect profile of KTP-NH₂ and IbKTP-NH₂ support the existence of opioid-based mechanisms in their analgesic actions. The conjugation of a strong analgesic activity with the absence of the major side-effects associated to opioids highlights the potential of both KTP-NH₂ and IbKTP-NH₂ as advantageous alternatives over current opioids.
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Lee WJ, Chung HH, Cheng YZ, Lin HJ, Cheng JT. Rhodiola-water extract induces β-endorphin secretion to lower blood pressure in spontaneously hypertensive rats. Phytother Res 2012. [PMID: 23192943 DOI: 10.1002/ptr.4900] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Rhodiola rosea (Rhodiola) is grown at high altitudes and northern latitudes. It is mainly used clinically as an adaptogen, but antihypertensive effects have been reported for the extract. These have not been well investigated, so in the present study, we evaluated the effect of Rhodiola-water extract on blood pressure in spontaneously hypertensive rats (SHRs) and investigated the potential mechanism(s) for this action. In conscious male SHRs, systolic blood pressure (SBP) and heart rate were recorded using the tail-cuff method. Plasma β-endorphin was measured by enzyme-linked immunosorbent assay. Rhodiola-water extract decreased SBP in SHRs in a dose-dependent manner, and this action was more significant than that in normal group named Wistar-Kyoto (WKY) rats. This reduction of SBP in SHRs was inhibited by pretreatment with the selective opioid μ-receptor antagonist, cyprodime, but not by naloxonazine, an antagonist specific to opioid μ1-receptor. Also, the SBP-lowering action of Rhodiola-water extract was attenuated in adrenalectomized SHRs. Moreover, Rhodiola-water extract dose-dependently increased β-endorphin release in SHRs, and the elevation of β-endorphin in SHRs was higher than that in WKY. Thus, we suggest that Rhodiola-water extract can induce release of β-endorphin to lower SBP in SHRs.
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Affiliation(s)
- Wei-Jing Lee
- Department of Emergency Medicine, Chi-Mei Medical Center, Yong Kang, Tainan City, 73101, Taiwan
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Pereira SL, Kummerle AE, Fraga CAM, Barreiro EJ, Sudo RT, Zapata-Sudo G. Vasodilator and antihypertensive effects of a novelN-acylhydrazone derivative mediated by the inhibition of L-type Ca2+channels. Fundam Clin Pharmacol 2012; 28:29-41. [DOI: 10.1111/j.1472-8206.2012.01076.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 06/25/2012] [Accepted: 08/07/2012] [Indexed: 11/29/2022]
Affiliation(s)
- Sharlene Lopes Pereira
- Programa de Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
| | - Arthur Eugen Kummerle
- Instituto de Ciências Exatas, Universidade Federal Rural do Rio de Janeiro; Seropédica RJ 23890-000 Brazil
| | - Carlos Alberto Manssour Fraga
- Programa de Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
- Programa de Pós-Graduação em Farmacologia e Química Medicinal, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
| | - Eliezer Jesus Barreiro
- Programa de Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
- Programa de Pós-Graduação em Farmacologia e Química Medicinal, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
| | - Roberto Takashi Sudo
- Programa de Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
- Programa de Pós-Graduação em Farmacologia e Química Medicinal, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
| | - Gisele Zapata-Sudo
- Programa de Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
- Programa de Pós-Graduação em Farmacologia e Química Medicinal, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ 21941-590 Brazil
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Bi YF, Wang ZJ, Guan RF, Ye YT, Chen YY, Zhang YB, Liu HM. Design, synthesis and vasodilative activity of tanshinone IIA derivatives. Bioorg Med Chem Lett 2012; 22:5141-3. [DOI: 10.1016/j.bmcl.2012.05.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Revised: 04/23/2012] [Accepted: 05/07/2012] [Indexed: 11/26/2022]
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Chen W, Chung HH, Cheng JT. Opiate-induced constipation related to activation of small intestine opioid μ2-receptors. World J Gastroenterol 2012; 18:1391-6. [PMID: 22493554 PMCID: PMC3319967 DOI: 10.3748/wjg.v18.i12.1391] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 09/24/2011] [Accepted: 01/18/2012] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the role of opioid μ-receptor subtype in opiate-induced constipation (OIC).
METHODS: The effect of loperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension. The ileum strips were precontracted with 1 μmol/L acetylcholine (ACh). Then, decrease in muscle tone (relaxation) was characterized after cumulative administration of 0.1-10 μmol/L loperamide into the organ bath, for a concentration-dependent study. Specific blockers or antagonists were used for pretreatment to compare the changes in loperamide-induced relaxation.
RESULTS: In addition to the delay in intestinal transit, loperamide produced a marked relaxation in isolated ileum precontracted with ACh, in a dose-dependent manner. This relaxation was abolished by cyprodime, a selective opioid μ-receptor antagonist, but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors. Also, treatment with opioid μ-1 receptor agonist failed to modify the muscle tone. Moreover, the relaxation by loperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K+ (KATP) channels, and by protein kinase A (PKA) inhibitor, but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate (cAMP).
CONCLUSION: Loperamide induces intestinal relaxation by activation of opioid μ-2 receptors via the cAMP-PKA pathway to open KATP channels, relates to OIC.
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Elkalioubie A, Allorge D, Robriquet L, Wiart JF, Garat A, Broly F, Fourrier F. Near-fatal tramadol cardiotoxicity in a CYP2D6 ultrarapid metabolizer. Eur J Clin Pharmacol 2011; 67:855-8. [PMID: 21691803 DOI: 10.1007/s00228-011-1080-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 05/31/2011] [Indexed: 11/29/2022]
Abstract
BACKGROUND Tramadol is a synthetic, centrally acting analgesic for the treatment of moderate to severe pain. The marketed tramadol is a racemic mixture containing 50% (+)tramadol and 50% (-)tramadol and is mainly metabolized to O-desmethyltramadol (M1) by the cytochrome P450 CYP2D6. Tramadol is generally considered to be devoid of any serious adverse effects of traditional opioid receptor agonists, such as respiratory depression and drug dependence. CASE REPORT A 22-year-old Caucasian female patient was admitted to our ICU in refractory cardiac arrest requiring extracorporeal membrane oxygenation. This aggressive support allowed resolution of multi-organ dysfunction syndrome. Repeated blood analyses using liquid chromatography-tandem mass spectrometry confirmed high concentrations of both tramadol and its main metabolite O-desmethyltramadol. Genotyping of CYP2D6 revealed the patient to be heterozygous for a duplicated wild-type allele, predictive of a CYP2D6 ultrarapid metabolizer (UM) phenotype, confirmed by calculation of the tramadol/M1 (MR1) metabolic ratio at all time points. DISCUSSION We here report a case of near-fatal isolated tramadol cardiotoxicity. Because of the inhibition of norepinephrine reuptake, excessive blood epinephrine levels in this CYP2D6R UM patient following excessive tramadol ingestion could explain the observed strong myocardial stunning. This patient admitted intermittent tramadol consumption to gain a "high" sensation. In patients with excessive morphinomimetic effects, levels of tramadol and its main metabolite M1could be measured, ideally combined with CYP2D6 genotyping, to identify individuals at risk of tramadol-related cardiotoxicity. Tramadol treatment could be optimized in these at-risk individuals, consequently improving patient outcome and safety.
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Affiliation(s)
- Ahmed Elkalioubie
- Service de Réanimation Polyvalente, Hôpital Roger Salengro, CHRU Lille, Rue Emile Laine, 59037, Lille Cedex, France.
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Girgis AS, Ismail NS, Farag H. Facile synthesis, vasorelaxant properties and molecular modeling studies of 2-amino-8a-methoxy-4H-pyrano[3,2-c]pyridine-3-carbonitriles. Eur J Med Chem 2011; 46:2397-407. [DOI: 10.1016/j.ejmech.2011.03.023] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 03/06/2011] [Accepted: 03/12/2011] [Indexed: 11/25/2022]
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Pharmacological activity of novel 2-hydroxyacetophenone isatin derivatives on cardiac and vascular smooth muscles in rats. J Cardiovasc Pharmacol 2011; 57:20-7. [PMID: 21233640 DOI: 10.1097/fjc.0b013e3181fd341c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Isatin (1H-indole-2,3 dione) is an endogenous compound with biological activities. Many of its derivatives have pharmacological effects, including inhibition of cyclic guanosine monophosphate levels in cardiac tissue; sedative-hypnotic profiles; anticonvulsant, analgesic, antithermic, and anti-inflammatory activities; and anxiolytic, antimicrobial, and proapoptotic effects. Carbamates derived from isatin have a vasorelaxant profile. This study investigated the activity of 2 novel 2-hydroxyacetophenone derivatives of isatin (named MB101 and MB130) on the contractility of rat aorta and papillary muscles. Both compounds induced a concentration-dependent relaxation (5-100 μM) in the endothelium-intact aorta that was abolished by N-nitro-L-arginine methyl ester. Atropine, a muscarinic receptor antagonist, significantly prevented vasodilatation of 100 μM MB101. In contrast, atropine caused no significant alteration in MB130-induced vasorelaxation. Naloxone, a nonselective opioid receptor antagonist, completely prevented the relaxing effect of MB101 and MB130 at all concentrations. In papillary muscles, only MB130 induced a significant depression, and this contractile response was not altered by propranolol and atropine. Both the compounds reduced systolic and diastolic pressures in a dose-dependent manner in anesthetized rats. The 2-hydroxyacetophenones produced direct effects on vascular tonus through either muscarinic or opioid pathways. MB130 produced cardiac depression by opioid receptors and bradykinin because pretreatment HOE140 or with naloxone, an antagonist of type-2, bradykinin were able to partially block the decrease in twitch amplitude in papillary muscles induced by MB130. These findings provide information for designing new strategies for the treatment of cardiovascular disorders.
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Chen ZC, Shieh JP, Chung HH, Hung CH, Lin HJ, Cheng JT. Activation of peripheral opioid µ-receptors in blood vessel may lower blood pressure in spontaneously hypertensive rats. Pharmacology 2011; 87:257-64. [PMID: 21494057 DOI: 10.1159/000326084] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 02/14/2011] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS The role of opioid receptors in the regulation of vascular function remains unclear. In the current study, we evaluated the ability of loperamide, a peripheral opioid receptor agonist, to regulate blood pressure in spontaneously hypertensive rats (SHRs) and examined the mechanism(s) by which loperamide exerts its effects. METHODS In male SHRs, mean arterial pressure (MAP) was measured and hemodynamic analysis was recorded. Additionally, the isometric tension of aortic rings isolated from SHRs was determined. RESULTS Loperamide dose-dependently decreased MAP in SHRs but not in the normal group of Wistar-Kyoto rats. This reduction of MAP in conscious SHRs was abolished by the selective opioid μ-receptor antagonist cyprodime, but not by naloxonazine, the μ(1)-opioid receptor antagonist. However, cardiac output was not altered by loperamide in anesthetized SHRs. Moreover, loperamide-induced relaxation in isolated aortic rings precontracted with phenylephrine or vasopressin. This relaxation was abolished by cyprodime, but not by naloxonazine. Loperamide-induced relaxation was also attenuated by glibenclamide, an ATP-sensitive potassium (K(ATP)) channel blocker. Additionally, vasodilatation by loperamide was reduced by an inhibitor of protein kinase A (PKA) and enhanced by an inhibitor of phosphodiesterases. CONCLUSION We suggest that loperamide can lower MAP in SHRs via μ(2)-opioid receptor-dependent cAMP-PKA pathway that induces vascular relaxation by opening K(ATP) channels.
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Affiliation(s)
- Zhih-Cherng Chen
- Department of Cardiology, Chi-Mei Medical Center, Yong Kang, Tainan City, Taiwan, ROC
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Lu CC, Chung HH, Cheng JT. Prostatic relaxation induced by loperamide is mediated through activation of opioid μ-2 receptors in vitro. Exp Ther Med 2011; 2:281-285. [PMID: 22977498 DOI: 10.3892/etm.2011.201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 12/06/2010] [Indexed: 11/06/2022] Open
Abstract
The merit of opioid μ-receptor activation in the improvement of benign prostatic hyperplasia (BPH) remains obscure. In the present study, we used loperamide to identify the subtype of opioid μ-receptors involved in prostatic relaxation and investigate the possible mechanism of this relaxation. Prostate strips were isolated from 12-week-old male Wistar rats for identification of isometric tension. The prostate strips were precontracted with either 1 μmol/l phenylephrine or 50 mmol/l KCl. The decrease in muscle tone (relaxation) was then characterized after cumulative administration of loperamide (0.1 to 10 μmol/l) into the organ bath for the concentration-dependent study. Pretreatment with specific blockers or antagonists was carried out to compare the changes in loperamide-induced relaxation. Loperamide produced a marked relaxation in the isolated prostates precontracted with phenylephrine or KCl in a dose-dependent manner. This relaxation was abolished by cyprodime, a selective opioid μ-receptor antagonist, but was not modified by naloxonazine at a dose sufficient to block the opioid μ-1 receptors. Treatment with an agonist for opioid μ-1 receptors also failed to modify the muscle tone. Moreover, the relaxation by loperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K(+) channels. In addition, this action of loperamide was abolished by protein kinase A (PKA) inhibitor and enhanced by the inhibitor of phosphodiesterase for cyclic AMP (cAMP). Our results suggest that loperamide induces prostatic relaxation through activation of opioid μ-2 receptors via the cAMP-PKA pathway to open ATP-sensitive K(+) channels.
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Affiliation(s)
- Chih-Cheng Lu
- Department of Surgery, Chi-Mei Medical Center, Liou-Ying
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Synthesis and vasodilation activity of some novel bis(3-pyridinecarbonitrile) derivatives. Eur J Med Chem 2010; 45:5176-82. [DOI: 10.1016/j.ejmech.2010.08.032] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 08/03/2010] [Accepted: 08/10/2010] [Indexed: 11/22/2022]
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Hamad Elgazwy ASS, Ismail NS, Elzahabi HS. A convenient synthesis and molecular modeling study of novel purine and pyrimidine derivatives as CDK2/cyclin A3 inhibitors. Bioorg Med Chem 2010; 18:7639-50. [DOI: 10.1016/j.bmc.2010.08.033] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2010] [Revised: 08/10/2010] [Accepted: 08/16/2010] [Indexed: 11/29/2022]
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Bi YF, Xu HW, Liu XQ, Zhang XJ, Wang ZJ, Liu HM. Synthesis and vasodilative activity of tanshinone IIA derivatives. Bioorg Med Chem Lett 2010; 20:4892-4. [DOI: 10.1016/j.bmcl.2010.06.076] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 06/09/2010] [Accepted: 06/14/2010] [Indexed: 10/19/2022]
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Raimundo JM, Pontes LB, Antunes F, Sudo RT, Trachez MM, Zapata-Sudo G. COMPARATIVE EFFECTS OF TRAMADOL ON VASCULAR REACTIVITY IN NORMOTENSIVE AND SPONTANEOUSLY HYPERTENSIVE RATS. Clin Exp Pharmacol Physiol 2008; 35:1197-203. [DOI: 10.1111/j.1440-1681.2008.04979.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Liu YC, Wang YJ, Wu PY, Wu SN. Tramadol-induced block of hyperpolarization-activated cation current in rat pituitary lactotrophs. Naunyn Schmiedebergs Arch Pharmacol 2008; 379:127-35. [PMID: 18818902 DOI: 10.1007/s00210-008-0353-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 09/09/2008] [Indexed: 01/08/2023]
Abstract
The hyperpolarization-activated cation current (I (h)) in rat pituitary lactotrophs (GH(3) cells) was characterized. Tramadol-induced block of this current was investigated. Effects of various related compounds on I (h) in GH(3) cells were also compared. Tramadol caused a time- and concentration-dependent reduction in the amplitude of I (h) with an IC(50) value of 13.6 microM. ZD7288 (30 microM), CsCl (2 mM), and propofol (30 microM) were effective in suppressing the amplitude of I (h). 2',5'-dideoxyadenosine (100 microM) suppressed I (h), while sp-cAMPS (100 microM) had no effect on it. Tramadol (10 microM) shifted the activation curve of I (h) to a more negative potential by approximately -20 mV, although no change in the slope factor was observed. Under current-clamp configuration, tramadol (10 microM) could reduce the firing frequency of action potentials. Intracellular Ca(2+) measurements revealed its ability to reduce spontaneous Ca(2+) oscillations in GH(3) cells. The results suggests that during cell exposure to tramadol used at clinically relevant concentration, the tramadol-mediated inhibition of I (h) could be direct and mediated via a non-opioid mechanism and would be one of the ionic mechanisms underlying reduced cell excitability.
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Affiliation(s)
- Yen-Chin Liu
- Department of Anesthesiology, National Cheng Kung University Medical College, Tainan, Taiwan
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Maroñas PA, Sudo RT, Corrêa MB, Pinto ÂC, Garden SJ, Trachez MM, Zapata-Sudo G. VASODILATORY ACTIVITY OF NOVEL CARBAMATE DERIVATIVES OF ISATIN. Clin Exp Pharmacol Physiol 2008; 35:1091-6. [DOI: 10.1111/j.1440-1681.2008.04959.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Daubin C, Quentin C, Goullé JP, Guillotin D, Lehoux P, Lepage O, Charbonneau P. Refractory shock and asystole related to tramadol overdose. Clin Toxicol (Phila) 2008; 45:961-4. [PMID: 17852155 DOI: 10.1080/15563650701438847] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Tramadol use is largely considered safe. However, several lethal cases of tramadol intoxication were reported, suggesting an underestimated toxicity. We report for a tramadol overdose case in combination with other central nervous system depressants, leading to refractory shock requiring extracorporeal life support. CASE REPORT A 33-year-old man was admitted in our intensive care unit for drug intoxication with coma, seizures, and hypotension without signs of heart failure. A few hours later, he developed a ventricular tachycardia, followed by a brief cardiac arrest in asystole with refractory shock requiring an extracorporeal life support, vasopressors, and hemofiltration. With this aggressive support, his overall status gradually improved. Repeated echocardiography showed an improvement in the cardiac function. The patient was weaned off extracorporeal life support on day eight and discharged on day 12. On admission, a urine analysis, using gas chromatography-mass spectrometry, showed high peaks of tramadol and desmethyltramadol with the presence of hydroxyzine, gabapentine, and clonazepam. The tramadol blood concentration measured by the high-performance liquid chromatography method-diode array detector was 23.9 mg/L, much higher than many previously reported fatal overdoses. No other drugs with potential cardiac toxicity, such as beta-blockers, calcium antagonists, antiarrythmic, antidepressants, meprobamate, or other xenobiotics were detected. CONCLUSION This case illustrates that tramadol overdose may cause refractory shock and asystole when taken in combination with CNS depressants, and reminds all physicians to be vigilant with regard to the potential toxic effects of tramadol.
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Affiliation(s)
- Cédric Daubin
- Department of Medical Intensive Care, Caen University Hospital, Caen Cedex, France.
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Abstract
This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, CUNY, 65-30 Kissena Blvd., Flushing, NY 11367, United States.
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Cho HC, Sohn JT, Park KE, Shin IW, Chang KC, Lee JW, Lee HK, Chung YK. Inhibitory effect of tramadol on vasorelaxation mediated by ATP-sensitive K+ channels in rat aorta. Can J Anaesth 2007; 54:453-60. [PMID: 17541074 DOI: 10.1007/bf03022031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE Tramadol produces a conduction block similar to lidocaine by exerting a local anesthetic-like effect. The aims of this in vitro study were to determine the effects of tramadol on the vasorelaxant response induced by the adenosine triphosphate-sensitive K(+) (K(ATP)) channel opener, levcromakalim, in an endothelium-denuded rat aorta, and to determine whether this effect of tramadol is stereoselective. METHODS The effects of tramadol (racemic, R(-) and S(+): 10(-6), 10(-5), 5 x 10(-5) M), and glibenclamide on the levcromakalim dose-response curve were assessed in aortic rings that had been pre-contracted with phenylephrine. In the rings pretreated independently with naloxone, and glibenclamide, the levcromakalim dose-response curves were generated in the presence or absence of tramadol. The effect of tramadol on the dose-response curve of diltiazem was assessed. RESULTS Racemic, R(-) and S(+) tramadol (10(-5), 5 x 10(-5) M) attenuated (P < 0.0001) levcromakalim-induced relaxation in the ring with or without naloxone in a dose-dependent manner. The magnitude of the R(-)-tramadol-induced attenuation of vasorelaxant response induced by levcromakalim was greater (P < 0.05) than that induced by S(+)-tramadol. Glibenclamide almost abolished the levcromakalim-induced relaxation. Tramadol, 5 x 10(-5) M, did not significantly alter the diltiazem-induced relaxation. CONCLUSION These results suggest that a supraclinical dose (10(-5) M) of tramadol [racemic, R(-) and S(+)] attenuates the vasorelaxation mediated by the K(ATP) channels in the rat aorta. The R(-) tramadol-induced attenuation of vasorelaxation induced by levcromaklim was more potent than that induced by S(+) tramadol. This attenuation is independent of opioid receptor activation.
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Affiliation(s)
- Hyoung-Chan Cho
- Department of Anesthesia and Pain Medicine, Gyeongsang National University Hospital, 90 Chilam-dong, Jinju, Gyeongnam, Republic of Korea
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Ali I, Gupta VK, Aboul-Enein HY, Singh P, Sharma B. Role of racemization in optically active drugs development. Chirality 2007; 19:453-63. [PMID: 17393472 DOI: 10.1002/chir.20397] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
U.S. Food and Drug Administration issues certain guidelines for marketing of optically active drugs as some enantiomers racemize into human body, leading to the generation of other antipodes, which may be toxic or ballast to the human beings. Moreover, racemization reduces the administrated dosage concentration as optically active enantiomer converted into its inactive counter part. Therefore, the study of racemization of such type of drugs is an important and urgent need of today. This article describes in vitro and in vivo racemization of optically active drugs. The racemization process of various optically active drugs has been discussed considering the effect of different variables i.e. pH, temperature, concentration of the drug, ionic concentration, etc. Attempts have also been made to discuss the mechanisms of racemization. Besides, efforts have been made to suggest the safe dosages of such type of drugs too.
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Affiliation(s)
- Imran Ali
- Department of Chemistry, Faculty of Natural Sciences, Jamia Millia Islamia University, Jamia Nagar, New Delhi, India
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Girgis AS, Kalmouch A, Ellithey M. Synthesis of novel vasodilatory active nicotinate esters with amino acid function. Bioorg Med Chem 2006; 14:8488-94. [PMID: 16973365 DOI: 10.1016/j.bmc.2006.08.041] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2006] [Revised: 08/24/2006] [Accepted: 08/28/2006] [Indexed: 11/26/2022]
Abstract
A variety of N-[(ethyl-4,6-diaryl-3-pyridinecarboxylate)-2-yl]amino acid esters 6a-h were synthesized through the reaction of 2-bromonicotinates 4 with a number of primary amino acid ester hydrochlorides 5 in refluxing tetrahydrofuran in the presence of triethylamine as dehydrohalogenating agent. Similarly, reaction of 4 with N-glycylglycine ethyl ester hydrochloride 7 'as a representative example of dipeptide derivative' afforded smoothly the corresponding N-[(ethyl-4,6-diaryl-3-pyridinecarboxylate)-2-yl]-N'-glycylglycine ethyl ester analogues 8. However, reaction of 4 with 5 in refluxing pyridine yielded the unexpected 2-aminonicotinate esters 9. Vasodilation activity screening for the synthesized nicotinate esters was investigated in vitro on the contractile response of vascular thoracic aorta smooth muscle from Wistar rats, where all the tested compounds exhibit considerable vasodilatory properties. In addition, few prepared compounds especially, 6b, 6h and 9b reveal remarkable vasodilation potency (IC(50)).
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Affiliation(s)
- Adel S Girgis
- Pesticide Chemistry Department, National Research Centre, Dokki, 12622 Cairo, Egypt.
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Shin IW, Sohn JT, Park KE, Chang KC, Choi JY, Lee HK, Chung YK. A Supraclinical Dose of Tramadol Stereoselectively Attenuates Endothelium-Dependent Relaxation in Isolated Rat Aorta. Anesth Analg 2006; 103:366-71, table of contents. [PMID: 16861418 DOI: 10.1213/01.ane.0000225913.64876.d2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Tramadol, a combination of R(-) and S(+) enantiomers, inhibits both the acetylcholine-mediated response of muscarinic receptors and the muscarine-induced accumulation of cyclic guanosine monophosphate. Our goals in this in vitro study were to investigate the effects of tramadol on endothelium-dependent relaxation induced by acetylcholine, to determine whether this effect of tramadol is stereoselective, and to elucidate the associated cellular mechanism in rat aorta. In endothelium-intact rings precontracted with phenylephrine with or without naloxone, dose-response curves for acetylcholine, histamine, and calcium ionophore A23187 were generated in the presence and absence of tramadol (racemic, R(-) and S(+)). Sodium nitroprusside dose-response curves were generated in the presence and absence of racemic tramadol. Racemic tramadol (5 x 10(-5) 10(-4) M) attenuated acetylcholine-induced relaxation in the rings with or without naloxone. R(-) tramadol, 5 x 10(-5) M, attenuated acetylcholine-induced relaxation, whereas S(+) tramadol, 5 x 10(-5) M, did not. Racemic tramadol (10(-4) M) had no effect on dose-response curves for calcium ionophore A23187 or sodium nitroprusside. Taken together, these results indicate that tramadol, at a supraclinical dose (5 x 10(-5) M), stereoselectively attenuates endothelium-dependent relaxation via an inhibitory effect at levels proximal to nitric oxide synthase activation on a pathway involving nonspecific endothelial receptor activation.
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Affiliation(s)
- Il-Woo Shin
- Department of Anesthesia and Pain Medicine, Gyeongsang National University College of Medicine, Jinju, Gyeongnam, Republic of Korea
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Berrocoso E, Micó JA, Ugedo L. In vivo effect of tramadol on locus coeruleus neurons is mediated by alpha2-adrenoceptors and modulated by serotonin. Neuropharmacology 2006; 51:146-53. [PMID: 16730359 DOI: 10.1016/j.neuropharm.2006.03.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Revised: 03/10/2006] [Accepted: 03/10/2006] [Indexed: 11/29/2022]
Abstract
Tramadol is a centrally-acting analgesic endowed with opioid, noradrenergic and serotonergic properties. Various data suggest that, in addition to its analgesic effect, tramadol may have antidepressant and anxiolytic-like effects. This study investigates, through single-unit extracellular recording techniques, the in vivo effects of tramadol on locus coeruleus (LC) neurons and its possible effects on alpha(2)-adrenoceptors, opioid receptors and the 5-HT system. Tramadol produced a dose-dependent and complete inhibition of LC activity (ED(50)=2.1mg/kg). This inhibitory effect was prevented and reversed by the selective alpha(2)-adrenoceptor antagonist, idazoxan, but not by the opioid receptor antagonist, naloxone. The inhibition of the synthesis of 5-HT by p-chlorophenylalanine and the pre-administration of the 5-HT(1A) receptor agonist, 8-OH-DPAT at 40microg/kg, caused a significant potentiation of the tramadol effect decreasing the ED(50) by 53% and 67% respectively. Lower doses of 8-OH-DPAT, of 1 and 4microg/kg, did not significantly modify the tramadol effect. In summary, the results indicate that tramadol elicits an inhibitory effect on LC neurons in vivo through alpha(2)-adrenoceptors. Moreover, this effect is modulated by the 5-HT system and particularly by 5-HT(1A) receptors.
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Affiliation(s)
- Esther Berrocoso
- Pharmacology and Neuroscience Research Group, Department of Neuroscience (Pharmacology and Psychiatry), School of Medicine, University of Cádiz, Plaza Falla 9, E-11003 Cádiz, Spain
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