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Angel-Isaza AM, Bustamante-Cristancho LA, Uribe-B FL. Successful Outcome Following Intravenous Lipid Emulsion Rescue Therapy in a Patient with Cardiac Arrest Due to Amitriptyline Overdose. AMERICAN JOURNAL OF CASE REPORTS 2020; 21:e922206. [PMID: 32447341 PMCID: PMC7274498 DOI: 10.12659/ajcr.922206] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND The management of patients with tricyclic antidepressant drug overdose can be a challenge for the emergency department physician. Tricyclic antidepressants block alpha-adrenergic receptors and the anticholinergic effects may lead to cardiotoxicity, resulting in arrhythmias and hypotension that can lead to patient mortality. This report is of a case of a 28-year-old woman who presented with cardiac arrest due to amitriptyline overdose and who responded to intravenous lipid emulsion (ILE) therapy. CASE REPORT A 28-year-old woman was admitted to the emergency department with amitriptyline overdose. She suffered a cardiac arrest followed by cardiovascular and neurological complications. Hypotension and lack of a pulse did not respond to treatment with high-dose sodium, but she stabilized following treatment with ILE. The prompt response from the emergency team guaranteed rapid intervention that may have influenced the successful results. CONCLUSIONS Despite the frequency and severity of poisoning with tricyclic antidepressants, there is little consensus among physicians regarding patient management. This case showed the successful use of ILE as rescue therapy in a patient in cardiac arrest following amitriptyline overdose. However, the successful outcome obtained in this case is not a recommendation for the use of ILE as a first-line treatment for the management of patients with tricyclic antidepressant drug overdose. Controlled clinical studies are required to evaluate the safety and efficacy of ILE in the management of tricyclic antidepressant drug overdose.
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Affiliation(s)
| | - Luis Alfonso Bustamante-Cristancho
- Emergency Department, Fundación Valle del Lili, Santiago de Cali, Colombia.,Intensive Care Unit, Fundación Valle del Lili, Santiago de Cali, Colombia
| | - Francisco L Uribe-B
- Clinical Research Center (Centro de Investigaciones Clínicas), Fundación Valle del Lili, Santiago de Cali, Colombia
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2
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Abstract
Dologesic is a commonly prescribed analgesic in accident and emergency department. Yet report of overdose with this drug is not common. We report a case in which the patient developed cardiac arrest within an hour of ingestion. Dextropropoxyphene, a component of the drug Dologesic, used to be a common cause of fatalities after drug overdose in the seventies. It is highly toxic in overdose and therefore caution should be exercised when prescribing this drug.
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Affiliation(s)
- CY Man
- Prince of Wales Hospital, Accident & Emergency Department, Shatin, New Territories, Hong Kong
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3
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Abstract
Sodium bicarbonate is a well-known antidote for tricyclic antidepressant (TCA) poisoning. It has been used for over half a century to treat toxin-induced sodium channel blockade as evidenced by QRS widening on the electrocardiogram (ECG). The purpose of this review is to describe the literature regarding electrophysiological mechanisms and clinical use of this antidote after poisoning by tricyclic antidepressants and other agents. This article will also address the literature supporting an increased serum sodium concentration, alkalemia, or the combination of both as the responsible mechanism(s) for sodium bicarbonate's antidotal properties. While sodium bicarbonate has been used as a treatment for cardiac sodium channel blockade for multiple other agents including citalopram, cocaine, flecainide, diphenhydramine, propoxyphene, and lamotrigine, it has uncertain efficacy with bupropion, propranolol, and taxine-containing plants.
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4
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Affiliation(s)
- Savita Butola
- Border Security Force, Composite Hospital, Border Security Force Campus, Jalandhar Cantonmentt, Punjab, India
| | - Mr Rajagopal
- WHO Collaborating Centre for Policy and Training on Access to Pain Relief, Chairman, Pallium India, Trivandrum, Kerala, India
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5
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Ray WA, Liu Q, Shepherd BE. Performance of time-dependent propensity scores: a pharmacoepidemiology case study. Pharmacoepidemiol Drug Saf 2015; 24:98-106. [PMID: 25408360 PMCID: PMC4331352 DOI: 10.1002/pds.3727] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 07/22/2014] [Accepted: 09/23/2014] [Indexed: 11/06/2022]
Abstract
PURPOSE Pharmacoepidemiologic studies of acute effects of episodic exposures often must control for many time-dependent confounders. Marginal structural models permit this and provide unbiased estimates when confounders are on the causal pathway. However, if causal pathway confounding is minimal, analyses with time-dependent propensity scores, calculated for time periods defined by individual drug prescriptions, may have better efficiency. We justify time-dependent propensity scores and compare the performance of these methods in a case study from a previous investigation of the risk of medication toxicity death in current users of propoxyphene and hydrocodone, with both substantial time-dependent confounding and a large number of covariates. METHODS The cohort included Tennessee Medicaid enrollees who filled a qualifying study opioid prescription between 1992 and 2007. We identified 22 time-dependent covariates that accounted for most of the confounding in the original study. We compared analyses with all covariates in the regression model with those based on time-dependent propensity scores and those from marginal structural models. RESULTS We identified 489,008 persons with 1,771,295 propoxyphene and 4,088,754 hydrocodone prescriptions. The unadjusted hazard ratio (propoxyphene : hydrocodone) was 0.70 (95%CI, 0.46-1.07). Estimates from inclusion of all covariates in the model, time-dependent propensity score analysis with inverse probability of treatment weighting, and marginal structural models were 1.63 (1.04-2.57), 1.65 (1.01-2.72), and 1.64 (0.83-3.27), respectively. Findings varied little with use of alternative propensity score methods, time origin, or techniques for marginal structural model estimation. CONCLUSIONS Time-dependent propensity scores may be useful for pharmacoepidemiologic studies with time-varying exposures when causal pathway confounding is limited.
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Affiliation(s)
- Wayne A Ray
- Department of Health Policy (WAR), Vanderbilt University School of Medicine, Nashville, TN, USA
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Ray WA, Murray KT, Kawai V, Graham DJ, Cooper WO, Hall K, Stein CM. Propoxyphene and the risk of out-of-hospital death. Pharmacoepidemiol Drug Saf 2013; 22:403-12. [PMID: 23408551 PMCID: PMC3694329 DOI: 10.1002/pds.3411] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 12/20/2012] [Accepted: 01/02/2013] [Indexed: 11/08/2022]
Abstract
PURPOSE The opioid analgesic propoxyphene was withdrawn from the US market in 2010, motivated by concerns regarding fatality in overdose and adverse cardiac effects, including prolongation of the QT interval. These concerns were based on case reports, summary vital statistics, and surrogate endpoint studies. METHODS Using the linked Tennessee Medicaid database (1992-2007), we conducted a retrospective cohort study that compared risk of sudden cardiac, medication toxicity, and total out-of-hospital death for propoxyphene users with that for comparable nonusers of any prescribed opioid analgesic and users of hydrocodone, an opioid with similar indications. Cohort members had 1,873,500 propoxyphene prescriptions, 1,873,500 matched nonuser control periods, and 936,750 matched hydrocodone prescriptions. RESULTS Current propoxyphene users had no increased risk for sudden cardiac death (versus nonusers: hazard ratio [HR] = 1.00 [0.81-1.23]; versus current hydrocodone users: HR = 0.91 [0.68-1.21]) but did have increased risk for medication toxicity deaths (versus nonusers: HR = 1.85 [1.07-3.19], p = 0.027; versus current hydrocodone users: HR = 2.10 [0.87-5.10], p = 0.100). Because toxicity deaths were a small proportion of study deaths, total out-of-hospital mortality differed by less than 10% between the study groups and was not significantly elevated for propoxyphene (versus nonusers: HR = 1.09 [0.95-1.25]; versus current hydrocodone users: HR = 1.06 [0.87-1.29] ). CONCLUSIONS Our findings support the concern that propoxyphene has greater toxicity in overdose but do not provide evidence that it increases the risk of sudden cardiac death.
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Affiliation(s)
- Wayne A Ray
- Division of Pharmacoepidemiology, Department of Preventive Medicine, Nashville, TN 37212, USA.
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7
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Karch SB. Possible Strategies for the Diagnosis of Fatal Excited Delirium Syndrome. Acad Forensic Pathol 2012. [DOI: 10.23907/2012.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Excited Delirium Syndrome (ExDS) is a term traditionally used in forensic literature to describe the symptoms and signs seen in a subgroup of patients with delirium who die in an agitated state. Components of this syndrome are altered mental status, combativeness and/or aggressiveness, increased tolerance to significant pain, tachypnea, profuse sweating, severe agitation, elevated temperature, delirium, and noncompliance with law enforcement and medical personnel. The individual may display “superhuman” strength and wear clothing inappropriate for the environment. Patients with this presentation are almost guaranteed to cause difficulties for law enforcement officers and medical staff. This review is written in hopes of minimizing some of these difficulties by 1) increasing general awareness and specific knowledge about this condition, 2) explaining the neurochemical and neuroanatomical alterations that have been shown to cause those symptoms, and 3) by suggesting new lines of research that might identify easily measured biomarkers for the disease. If the disease mechanism can be deciphered, then it should be possible to devise effective strategies for treatment. It would also be of enormous value to the legal system. When defending a diagnosis before the court, physical evidence always trumps knowledge and experience. It would be far better to be able to present physical proof than to opine that the decedent's behavior was typical for the disease. In this aspect, ExDS is analogous to myocardial infarction: if a man dies suddenly, it is much easier to prove the cardiac origin of the event if an occlusive thrombus is found in a major coronary artery.
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Affiliation(s)
- Steven B. Karch
- (Royal College of Physicians, London). Royal London Hospital and Cardiac Pathology at the Stanford Transplant Laboratory. San Francisco Medical Examiner
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8
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Levine M, Brooks DE, Truitt CA, Wolk BJ, Boyer EW, Ruha AM. Toxicology in the ICU. Chest 2011; 140:795-806. [DOI: 10.1378/chest.10-2548] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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9
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Hoffman RS. Treatment of patients with cocaine-induced arrhythmias: bringing the bench to the bedside. Br J Clin Pharmacol 2011; 69:448-57. [PMID: 20573080 DOI: 10.1111/j.1365-2125.2010.03632.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Widespread use of cocaine and its attendant toxicity has produced a wealth of benchwork studies and small animal investigations that evaluated the effects of cocaine on the cardiovascular system. Despite this wealth of knowledge, very little is known about the frequency or types of arrhythmias in patients with significant cocaine toxicity. The likely aetiologies; catecholamine excess, sodium channel blockade, potassium channel blockade, calcium channel effects, or ischaemia may act alone or in concert to produce a vast array of clinical findings that are modulated by hyperthermia, acidosis, hypoxia and electrolyte abnormalities. The initial paper in the series by Wood & Dargan providing the epidemiological framework of cocaine use and abuse is followed by a detailed review of the electrophysiological effects of cocaine by O'Leary & Hancox. This review is designed to complement the previous papers and focuses on the diagnosis and treatment of patients with cocaine-associated arrhythmias.
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10
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Foianini A, Joseph Wiegand T, Benowitz N. What is the role of lidocaine or phenytoin in tricyclic antidepressant-induced cardiotoxicity? Clin Toxicol (Phila) 2010; 48:325-30. [DOI: 10.3109/15563650.2010.487050] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Stringer J, Welsh C, Tommasello A. Methadone-associated Q-T interval prolongation and torsades de pointes. Am J Health Syst Pharm 2009; 66:825-33. [PMID: 19386945 DOI: 10.2146/ajhp070392] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
PURPOSE The association of methadone with Q-T interval prolongation and torsades de pointes (TdP) is reviewed, and recommendations for preventing Q-T interval prolongation in methadone users are provided. SUMMARY Abnormalities in voltage-gated potassium channels have been shown to lead to prolonged action potentials that are expressed as long Q-T intervals, and methadone has been found to interact with the voltage-gated potassium channels of the myocardium. While cardiac arrhythmias in methadone users have been reported for several decades, specific reports of methadone-associated Q-T interval prolongation and TdP did not appear in the literature until the early part of the 21st century. Because not every patient experiences Q-T interval prolongation with methadone, recent research has elucidated risk factors that predispose patients to this adverse effect, including female sex, hypokalemia, high-dose methadone, drug interactions, underlying cardiac conditions, unrecognized congenital long Q-T interval syndrome, and predisposing DNA polymorphisms. Given the high mortality rates seen in untreated illicit opioid users and the clear efficacy of methadone in treating opioid addiction, the risk of using methadone, even in a patient with other risk factors for Q-T interval prolongation, may outweigh the alternative of no pharmacologic treatment. A baseline electrocardiogram (ECG), personal and family history of syncope, and a complete medication history should be obtained before a patient begins treatment with methadone. Given the apparent synergistic effects of parenteral methadone and chlorobutanol, oral methadone should be used whenever possible. CONCLUSION Q-T interval prolongation and TdP associated with the use of methadone are potentially fatal adverse effects. A thorough patient history and ECG monitoring are essential for patients treated with this agent, and alterations in treatment options may be necessary.
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Affiliation(s)
- John Stringer
- Pharmacy, Saint Barnabas Behavioral Health Center, Toms River, NJ 08754, USA.
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Al Khaja KAJ, Al-Haddad MK, Al-Offi AR, Abdulraheem MH, Sequeira RP. Use of dextropropoxyphene + acetaminophen fixed-dose combination in psychiatric hospital in Bahrain: is there a cause for concern? Fundam Clin Pharmacol 2009; 23:253-8. [DOI: 10.1111/j.1472-8206.2008.00662.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Afshari R, Maxwell S, Dawson A, Bateman DN. ECG Abnormalities in Co-proxamol (Paracetamol/Dextropropoxyphene) Poisoning. Clin Toxicol (Phila) 2008. [DOI: 10.1081/clt-66069] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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14
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Barkin RL, Barkin SJ, Barkin DS. Propoxyphene (dextropropoxyphene): a critical review of a weak opioid analgesic that should remain in antiquity. Am J Ther 2007; 13:534-42. [PMID: 17122535 DOI: 10.1097/01.mjt.0000253850.86480.fb] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Propoxyphene (dextropropoxyphene) is a synthetic weak opioid introduced into the United States in 1957. It is most frequently prescribed in combination with acetaminophen and/or aspirin. After its ubiquitous introductory phase, it was soon discovered that this drug's iatrogenic events (cardiotoxicity, seizures, etc.) far outweighed any perceived therapeutic benefit. Propoxyphene analgesia was equated with that of merely acetaminophen or aspirin independently. The propoxyphenes euphorigenic component has created a problem in its prescribing. Use of this agent in the elderly should be avoided because of its complex pharmacokinetics and pharmacodynamics. The pharmacokinetics, pharmacodynamics, and pharmacology of this drug are discussed thoroughly in this article, including its arrhythmogenicity. Additional noncardiovascular pharmacotherapies that produce QTc prolongation or arrhythmogenicity are described. A list of the cytochrome P450 2D6 pharmacotherapies that will interact with propoxyphene is provided in the article. The use of this agent is highly discouraged. The rationale for this is discussed fully within this article. The toxicity of this drug is partially related to nor-propoxyphene a non-opioid cardiotoxic metabolite. The mere warnings of fatalities within the package insert should alert any cautious prescriber on the dangers of this agent and dampen its prescribing potential.
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Affiliation(s)
- Robert L Barkin
- Department of Anesthesiology, Rush University Medical Center, Rush Pain Center, Chicago, Illinois 60612, USA.
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15
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Abstract
A novel clinical entity characterized by ST segment elevation in right precordial leads (V1 to V3), incomplete or complete right bundle branch block, and susceptibility to ventricular tachyarrhythmia and sudden cardiac death has been described by Brugada et al. in 1992. This disease is now frequently called "Brugada syndrome" (BrS). The prevalence of BrS in the general population is unknown. The suggested prevalence ranges from 5/1,000 (Caucasians) to 14/1,000 (Japanese). Syncope, typically occurring at rest or during sleep (in individuals in their third or fourth decades of life) is a common presentation of BrS. In some cases, tachycardia does not terminate spontaneously and it may degenerate into ventricular fibrillation and lead to sudden death. Both sporadic and familial cases have been reported and pedigree analysis suggests an autosomal dominant pattern of inheritance. In approximately 20% of the cases BrS is caused by mutations in the SCN5A gene on chromosome 3p21-23, encoding the cardiac sodium channel, a protein involved in the control of myocardial excitability. Since the use of the implantable cardioverter defibrillator (ICD) is the only therapeutic option of proven efficacy for primary and secondary prophylaxis of cardiac arrest, the identification of high-risk subjects is one of the major goals in the clinical decision-making process. Quinidine may be regarded as an adjunctive therapy for patients at higher risk and may reduce the number of cases of ICD shock in patients with multiple recurrences.
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Affiliation(s)
- Carlo Napolitano
- Molecular Cardiology Laboratories, IRCCS, Fondazione Salvatore Maugeri, Via Ferrata 8, 27100 Pavia, Italy
| | - Silvia G Priori
- Molecular Cardiology Laboratories, IRCCS, Fondazione Salvatore Maugeri, Via Ferrata 8, 27100 Pavia, Italy
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16
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Abstract
Drug- and toxin-associated seizures (DTS) may result from exposure to a wide variety of agents. Most DTS can be managed with supportive care. First-line anticonvulsant therapy should include benzodiazepines, unless agents require a specific antidote. Phenytoin is generally not expected to be useful for DTS and in some instances may be harmful. In this article the authors discuss the pathophysiology of DTS, the potential differential diagnosis, and the clinical presentation. They also review selected agents that cause DTS and provide an overview of how the clinician should approach the management of patients who have DTS.
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17
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Abstract
Drug- and toxin-associated seizures may result from exposure to a wide variety of agents. Obtaining a comprehensive history behind the exposure is generally more helpful than diagnostic testing. Most DTS may be managed with supportive care, including benzodiazepines, except in the case of agents that require a specific intervention or antidote.
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Affiliation(s)
- Brandon Wills
- Department of Emergency Medicine, University of Illinois, Chicago, Chicago, IL 60612, USA.
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18
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Abstract
The liver is the major site of biotransformation for most opioids. Thus, the disposition of these drugs may be affected in patients with liver insufficiency. The major metabolic pathway for most opioids is oxidation. The exceptions are morphine and buprenorphine, which primarily undergo glucuronidation, and remifentanil, which is cleared by ester hydrolysis. Oxidation of opioids is reduced in patients with hepatic cirrhosis, resulting in decreased drug clearance [for pethidine (meperidine), dextropropoxyphene, pentazocine, tramadol and alfentanil] and/or increased oral bioavailability caused by a reduced first-pass metabolism (for pethidine, dextropropoxyphene, pentazocine and dihydrocodeine). Although glucuronidation is thought to be less affected in liver cirrhosis, and clearance of morphine was found to be decreased and oral bioavailability increased. The consequence of reduced drug metabolism is the risk of accumulation in the body, especially with repeated administration. Lower doses or longer administration intervals should be used to remedy this risk. Special risks are known for pethidine, with the potential for the accumulation of norpethidine, a metabolite that can cause seizures, and for dextropropoxyphene, for which several cases of hepatotoxicity have been reported. On the other hand, the analgesic activity of codeine and tilidine depends on transformation into the active metabolites, morphine and nortilidine, respectively. If metabolism is decreased in patients with chronic liver disease, the analgesic action of these drugs may be compromised. Finally, the disposition of a few opioids, such as fentanyl, sufentanil and remifentanil, appears to be unaffected in liver disease.
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Affiliation(s)
- I Tegeder
- Center of Pharmacology, Johann Wolfgang Goethe-University of Frankfurt, Frankfurt am Main, Germany
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19
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Starmer CF. The cardiac vulnerable period and reentrant arrhythmias: targets of anti- and proarrhythmic processes. Pacing Clin Electrophysiol 1997; 20:445-54. [PMID: 9058848 DOI: 10.1111/j.1540-8159.1997.tb06203.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Because sudden cardiac death is usually preceded by a reentrant arrhythmia, the precipitating arrhythmia must be multicellular in origin. Therefore clinicians seeking to reduce the incidence of reentrant arrhythmias in their patients with antiarrhythmic drugs that alter propagation may reasonably question the applicability of drug classification schemes (e.g. Sicilian Gambit) that are based on measurements in single cells. This raises a major question: are measures of a drug's anti- and proarrhythmic potential in single cells predictive of its anti- and proarrhythmic properties in tissue? The problem is as follows. From single cell measurements, one expects Class I drugs to reduce excitability, thereby attenuating the occurrence of PVCs. Similarly, one expects Class III drugs to prolong refractoriness and reduce the occurrence of PVCs. We have found in simple models of cardiac tissue that sodium channel blockade (the target of Class I drugs) extends the vulnerable period of a propagating excitation wave, whereas potassium channel blockade (the target of Class III drugs) destabilizes the reentrant path in a manner that amplifies the likelihood of polymorphic tachyarrhythmias. Using analytical, numerical, and experimental studies, we determined that sodium channel blockade was proarrhythmic. In fact, we found that any intervention that slowed conduction was proarrhythmic because slowed conduction increases the vulnerable period and reduces the spatial requirements for sustained reentry. We also found that when obstacles were placed in the path of a propagating wave, reentry occurred when the conduction velocity was less than a critical value. Once reentry was established, we observed that the ECG displayed monomorphic QRS complexes when the reentrant path did not vary from cycle to cycle. Moreover, when the reentry path did vary from cycle to cycle, the ECG displayed polymorphic QRS complexes. The cycle-to-cycle variation in QRS morphology was caused by the spatial variability of the reentry path. The variability of reentry paths (and hence the degree of polymorphic variation in QRS complexes) was amplified by Class III agents. The results presented here show that multicellular proarrhythmic effects are derived from the same mechanisms that exhibit antiarrhythmic properties in single cells.
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Affiliation(s)
- C F Starmer
- Department of Medicine (Cardiology), Duke University Medical Center, Durham, North Carolina 27710, USA.
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20
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Abstract
Voltage-dependent ionic currents were recorded from squid giant fiber lobe neurons using the whole-cell patch-clamp technique. When applied to the bathing solution, methadone was found to block IK, I Na and I Ca. Both I Na and I Ca were reduced without apparent change in kinetics and exhibited IC(50)'s of 50-100 and 250-500 mu M, respectively, at +10 mV. In contrast, IK was reduced in a time-dependent manner that is well fit by a simple model of open channel block (K(D)= 32+/- or 2 mu M, +60 mV, 10 degrees Celsius). The mechanism of I(K) block was examined in detail and involves a direct action of methadone, a tertiary amine, on K channels rather than an opioid receptor-mediated pathway. The kinetics of I(K) block resemble those reported for internally applied long chain quaternary ammonium (QA) compounds; and recovery from I(K) block is QA-like in its slow time course and strong dependence on holding potential. A quaternary derivative of methadone (N-methyl-methadone) only reproduced the effects of methadone on I(K) when included in the pipette solution; this compound was without effect when applied externally. I(K) block thus appears to involve diffusion of methadone into the cytoplasm and occlusion of the open K channel at the internal QA blocking site by the protonated form of the drug. This proposed mode of action is supported by the pH and voltage dependence of block as well as by the observation that high external K+ speeds the rate of drug dissociation. In addition, the effect of methadone on I(K) evoked during prolonged (300 ms) depolarizations suggests that methadone block may interfere with endogenous K+ channel inactivation. The effects of temperature, methadone stereoisomers, and the methadone-like drugs propoxyphene and nor-propoxyphene on IK block were examined. Methadone was also found to block I(K) in GH3 cells and in chick myoblasts.
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Affiliation(s)
- F T Horrigan
- Hopkins Marine Station of Stanford University, Department of Biological Sciences, Pacific Grove, California 93950, USA
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21
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Whalley DW, Wendt DJ, Grant AO. Basic concepts in cellular cardiac electrophysiology: Part II: Block of ion channels by antiarrhythmic drugs. Pacing Clin Electrophysiol 1995; 18:1686-704. [PMID: 7491312 DOI: 10.1111/j.1540-8159.1995.tb06990.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Antiarrhythmic drugs have relative specificity for blocking each of the major classes of ion channels that control the action potential. The kinetics of block is determined by the state of the channel. Those channel states occupied at depolarized potentials generally have greater affinity for the blocking drugs. The kinetics of the drug-channel interaction is important in determining the blocking profile observed clinically. The increased mortality resulting from drug treatment in CAST and several atrial fibrillation trials has resulted in a shift in antiarrhythmic drug development from the Na+ channel blocking (Class I) drugs to the K+ channel blocking (Class III) drugs. While both Classes of drugs have a proarrhythmic potential, this may be less for the Class III agents. Their lack of negative inotropy also make them more attractive. It is important that the potential advantages of these agents be evaluated in controlled clinical trials. In several laboratories, the techniques of molecular biology and biophysics are being combined to determine the block site of available drugs. This information will aid in the future development of agents with greater specificity, and hopefully greater efficacy and safety than those currently in clinical use.
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Affiliation(s)
- D W Whalley
- Duke University Medical Center, Durham, North Carolina, USA
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22
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Stork CM, Redd JT, Fine K, Hoffman RS. Propoxyphene-induced wide QRS complex dysrhythmia responsive to sodium bicarbonate--a case report. JOURNAL OF TOXICOLOGY. CLINICAL TOXICOLOGY 1995; 33:179-83. [PMID: 7897759 DOI: 10.3109/15563659509000470] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Propoxyphene overdose is known to cause widening of the QRS complex on ECG. We report a case of a 54-year-old female who ingested approximately 100 propoxyphene hydrochloride tablets in a suicide attempt. She developed a wide complex dysrhythmia which responded to sodium bicarbonate therapy. Propoxyphene-induced wide complex dysrhythmia responsive to sodium bicarbonate therapy has not been previously reported in the literature.
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Affiliation(s)
- C M Stork
- New York City Poison Control Center, NY 10016
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Starmer CF, Biktashev VN, Romashko DN, Stepanov MR, Makarova ON, Krinsky VI. Vulnerability in an excitable medium: analytical and numerical studies of initiating unidirectional propagation. Biophys J 1993; 65:1775-87. [PMID: 8298011 PMCID: PMC1225913 DOI: 10.1016/s0006-3495(93)81233-5] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Cardiac tissue can display unusual responses to certain stimulation protocols. In the wake of a conditioning wave of excitation, spiral waves can be initiated by applying stimuli timed to occur during a period of vulnerability (VP). Although vulnerability is well known in cardiac and chemical media, the determinants of the VP and its boundaries have received little theoretical and analytical study. From numerical and analytical studies of reaction-diffusion equations, we have found that 1) vulnerability is an inherent property of Beeler-Reuter and FitzHugh-Nagumo models of excitable media; 2) the duration of the vulnerable window (VW) the one-dimensional analog of the VP, is sensitive to the medium properties and the size of the stimulus field; and 3) the amplitudes of the excitatory and recovery processes modulate the duration of the VW. The analytical results reveal macroscopic behavior (vulnerability) derived from the diffusion of excitation that is not observable at the level of isolated cells or single reaction units.
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Affiliation(s)
- C F Starmer
- Department of Medicine (Cardiology), Duke University Medical Center, Durham, North Carolina 27710
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Barber MJ, Wendt DJ, Starmer CF, Grant AO. Blockade of cardiac sodium channels. Competition between the permeant ion and antiarrhythmic drugs. J Clin Invest 1992; 90:368-81. [PMID: 1322937 PMCID: PMC443111 DOI: 10.1172/jci115871] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A number of basic and clinical studies suggest that elevation of external sodium concentrations, [Na]o, may reverse the cardiotoxic effect of local anesthetic-class drugs. The mechanisms of reversal are uncertain. The blocking action of lidocaine and disopyramide were studied over a range of [Na]o. Both whole-cell voltage clamp and single-channel recordings were performed on isolated rabbit myocytes at 17 and 22 degrees C, respectively. In the presence of lidocaine, an inactivated channel blocker, the level of steady-state block in response to pulse train stimulation was not affected by variations in [Na]o from 20 to 150 mM. Estimates of the rate of dissociation of drug from the channel also were unaffected. In contrast, steady-state block by disopyramide, a drug that blocks open channels, was decreased as [Na]o was increased. Single-channel measurements suggest that the influence of [Na]o on channel current amplitude was small, 12% for a 25 mM increase in [Na]o. This increase in single-channel current amplitude would affect drug-free channels only, in that our studies suggest that drug-associated channels do not conduct. The association rate constant of disopyramide with open single sodium channels was decreased from 10 x 10(6) to 5 x 10(6)/M per s by an increase in [Na]o from 120 to 180 mM. Elevation of [Na]o may reverse the blocking action of local anesthetic-class drugs by an increase in single-channel current amplitude or by a decrease in drug association rate with the sodium channel. The occurrence of the latter action depends on the mode of block of the specific agent.
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Affiliation(s)
- M J Barber
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27706
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Wendt DJ, Starmer CF, Grant AO. Kinetics of interaction of the lidocaine metabolite glycylxylidide with the cardiac sodium channel. Additive blockade with lidocaine. Circ Res 1992; 70:1254-73. [PMID: 1315638 DOI: 10.1161/01.res.70.6.1254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The recovery of the sodium channel from blockade by local anesthetic antiarrhythmic drugs is voltage dependent. Recovery from lidocaine-induced blockade is accelerated by hyperpolarization, whereas that from glycylxylidide (GX) blockade has been reported to be slowed by hyperpolarization. This striking difference occurs despite similarities in chemical structure. The fast recovery from GX block at depolarized potentials may lead to a partial reversal of lidocaine blockade when the two drugs are combined. We have examined the kinetics of interaction of GX with the cardiac sodium channel over a range of membrane potentials by measuring whole-cell currents in isolated rabbit myocytes under voltage clamp at 15 degrees C. In the absence of drug, slow inactivation developed with a time constant of 10.7 +/- 5.1 seconds (n = 6). During exposure to 74 mumol/l GX, block developed with a time constant of 7.0 +/- 3 seconds (n = 6). Because of the similar time course of slow inactivation and block, we used a high concentration of GX to induce a level of block sufficient for analysis. The onset of block was slower than that induced by lidocaine and was unaffected by variation of external sodium from 20 to 75 mmol/l. Use-dependent blockade of sodium channels was greater when pulse trains were applied from a holding potential of -100 than -140 mV. This suggested that recovery from GX block might be slower at -100 than -140 mV. Direct measurements gave time constants of recovery of 10.3 +/- 4.2 seconds at -100 mV (n = 6) and 4.1 +/- 0.4 seconds at -140 mV (n = 4). The combination of GX with lidocaine produced only additive blocking effects when pulse trains were applied from both holding potentials. Computer simulations of the requirements for the competitive displacement of a sodium channel blocker with slow kinetics by one with fast kinetics suggest that the recovery time constant of the fast drug must be 10-100-fold smaller than that of the slow drug. Rapid association kinetics effected by a large binding rate constant or a higher concentration of the fast blocking drug is also important. The simulations suggest that, for the interaction of GX and lidocaine, only additive blocking action should be observed over the range of stimulus frequencies used in these experiments.
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Affiliation(s)
- D J Wendt
- Department of Internal Medicine, Duke University Medical Center, Durham, N.C
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The Sicilian gambit. A new approach to the classification of antiarrhythmic drugs based on their actions on arrhythmogenic mechanisms. Task Force of the Working Group on Arrhythmias of the European Society of Cardiology. Circulation 1991; 84:1831-51. [PMID: 1717173 DOI: 10.1161/01.cir.84.4.1831] [Citation(s) in RCA: 363] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Queen's Gambit is an opening move in chess that provides a variety of aggressive options to the player electing it. This report represents a similar gambit (the Sicilian Gambit) on the part of a group of basic and clinical investigators who met in Taormina, Sicily to consider the classification of antiarrhythmic drugs. Paramount to their considerations were 1) dissatisfaction with the options offered by existing classification systems for inspiring and directing research, development, and therapy, 2) the disarray in the field of antiarrhythmic drug development and testing in this post-Cardiac Arrhythmia Suppression Trial (CAST) era, and 3) the desire to provide an operational framework for consideration of antiarrhythmic drugs that will both encourage advancement and have the plasticity to grow as a result of the advances that occur. The multifaceted approach suggested is, like the title of the article, a gambit. It is an opening rather than a compendium and is intended to challenge thought and investigation rather than to resolve issues. The article incorporates first, a discussion of the shortcomings of the present system for drug classification; second, a review of the molecular targets on which drugs act (including channels and receptors); third, a consideration of the mechanisms responsible for arrhythmias, including the identification of "vulnerable parameter" that might be most accessible to drug effect; and finally, clinical considerations with respect to antiarrhythmic drugs. Information relating to the various levels of information is correlated across categories (i.e., clinical arrhythmias, cellular mechanisms, and molecular targets), and a "spread sheet" approach to antiarrhythmic action is presented that considers each drug as a unit, with similarities to and dissimilarities from other drugs being highlighted. A complete reference list for this work would require as many pages as the text itself. For this reason, referencing is selective and incomplete. It is designed, in fact, to provide sufficient background information to give the interested reader a starting frame of reference rather than to recognize the complete body of literature that is the basis for this article.
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Starmer CF, Lastra AA, Nesterenko VV, Grant AO. Proarrhythmic response to sodium channel blockade. Theoretical model and numerical experiments. Circulation 1991; 84:1364-77. [PMID: 1653123 DOI: 10.1161/01.cir.84.3.1364] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND The use of flecainide and encainide was terminated in the Cardiac Arrhythmia Suppression Trial because of an excess of sudden cardiac deaths in the active treatment group. Such events might arise from reentrant rhythms initiated by premature stimulation in the presence of anisotropic sodium channel availability. Drugs that bind to sodium channels increase the functional dispersion of refractoriness by slowing (a result of the drug-unbinding process) the transition from an inexcitable state to an excitable state. It is interesting that encainide and flecainide unbind slowly (15-20 seconds), whereas lidocaine and moricizine unbind rapidly (0.2-1.3 seconds). METHODS AND RESULTS With a computer representation of a cable with Beeler-Reuter membrane properties, we found a small (6 msec) vulnerable window that occurred 338 msec after the last drive stimulus. Premature stimuli falling within the vulnerable window resulted in unidirectional block and reentrant activation. In the presence of a slowly unbinding drug, the window was delayed an additional 341 msec, and its duration was extended to 38 msec. The delay (antiarrhythmic effect) before the onset of the vulnerable window and its duration (proarrhythmic effect) were both dependent on the sodium channel availability and the recovery process. Both effects were also prolonged when sodium channel availability was reduced by membrane depolarization. Defining the proarrhythmic potential as the duration of the vulnerable window, we found that hypothetical use-dependent class I drugs have a greater proarrhythmic potential than non-use-dependent drugs. CONCLUSIONS The antiarrhythmic and proarrhythmic properties of pure sodium channel antagonists are both dependent on sodium channel availability. Consequently, the price for increased antiarrhythmic efficacy (suppressed premature ventricular contractions) is an increased proarrhythmic vulnerability to unsuppressed premature ventricular contractions.
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Affiliation(s)
- C F Starmer
- Department of Medicine, Duke University Medical Center, Durham, N.C. 27710
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Barber MJ, Starmer CF, Grant AO. Blockade of cardiac sodium channels by amitriptyline and diphenylhydantoin. Evidence for two use-dependent binding sites. Circ Res 1991; 69:677-96. [PMID: 1651817 DOI: 10.1161/01.res.69.3.677] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cardiac toxicity is a frequent manifestation in amitriptyline overdose and is felt to be due, in part, to sodium channel blockade by the drug. Another agent with sodium channel blocking properties, diphenylhydantoin, has been used clinically to reverse cardiac conduction abnormalities induced by amitriptyline. This reversal of toxicity is believed to occur secondary to competition for the sodium channel binding site. We evaluated individually and in combination the effects of amitriptyline (0.4 microM) and diphenylhydantoin (10-80 microM) on the sodium current in isolated rabbit atrial and ventricular myocytes at 17 degrees C. Using the whole-cell variant of the patch-clamp technique, we found that both amitriptyline and diphenylhydantoin reduced the sodium current in a use-dependent fashion. The time constant of recovery (tau r) from block by amitriptyline at -130 mV was very slow (13.6 +/- 3.2 seconds), whereas tau r during diphenylhydantoin exposure was fast (0.71 +/- 0.21 seconds, p less than 0.0001 compared with amitriptyline). During exposure of cells to a mixture of the two drugs, tau r was found to be 6.6 +/- 1.8 seconds, but no evidence of direct competition between amitriptyline and diphenylhydantoin was seen. Attempts to fit the recovery data of the mixture to two exponentials resulted in no significant improvement in the fit when compared with that using a single exponential. Use of the sodium channel blocking agent lidocaine (similar kinetics to diphenylhydantoin) in competition with amitriptyline resulted in findings consistent with direct competition of these two drugs for a single binding site. These observations prompted us to evaluate the possibility that diphenylhydantoin was not acting at (and therefore not competing for) the same channel binding site as amitriptyline. Experiments altering pHi and pHo revealed dramatic differences between amitriptyline and diphenylhydantoin. When pHo was increased from 7.4 to 8.0, tau r was reduced approximately threefold (from 13.6 +/- 3.2 to 4.2 +/- 0.1 seconds, p less than 0.0001) during exposure to amitriptyline, but no effect was seen on tau r after exposure to diphenylhydantoin. Conversely, when pHi was increased from 7.3 to 8.0, tau r after amitriptyline was unaffected, but tau r after diphenylhydantoin markedly increased (from 0.71 +/- 0.21 to 2.60 +/- 1.30 seconds, p less than 0.001). Additionally, diphenylhydantoin block demonstrated profound voltage dependence across the range of -130 to -90 mV, whereas amitriptyline block appeared less voltage sensitive. Single-channel studies using patch-clamp techniques in isolated ventricular myocytes supported these data.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- M J Barber
- Department of Medicine, Duke University Medical Center, Durham, NC 22710
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Grant AO. The cardiac sodium channel: a target for antiarrhythmic drug action. Pacing Clin Electrophysiol 1990; 13:1541-52. [PMID: 1702535 DOI: 10.1111/j.1540-8159.1990.tb04037.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- A O Grant
- Duke University Medical Center, Durham, North Carolina 27706
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