Lidocaine potentiation of cocaine toxicity

Acute Cardiovascular Toxicity of Cocaine

Cocaine is one of the most commonly abused drugs and represents a major public health concern. Cocaine users frequently present to the emergency department, with chest pain being the most common presenting complaint. The incidence of acute myocardial infarction in patients with cocaine-associated chest pain is often quoted as 6%, but it is highly variable depending on the included population. Risk assessment can be challenging in these patients; serial assessment of electrocardiograms and troponins is often required. This review focuses on the assessment and management of patients presenting with cocaine-associated chest pain and cardiotoxicity. Specific treatments are discussed, including benzodiazepines, nitroglycerin, calcium channel blockers, and phentolamine, and how treatment priorities differ from patients with noncocaine presentations. The use of beta-blockers in this population remains controversial, and the literature around its use is reviewed. The most recent literature and recommendations for the use of percutaneous coronary intervention and fibrinolytics in cocaine-associated myocardial infarction is discussed as well. Cocaine-associated dysrhythmias are suggested to be the cause of sudden cardiac death in some users. The pathophysiology and evidence-based treatments for dysrhythmias are reviewed. This review provides evidence-based recommendations for the assessment and management of patients presenting with cocaine-associated cardiovascular toxicity.

Stimulant Drugs of Abuse and Cardiac Arrhythmias

Nonmedical use of prescription and nonprescription drugs is a worldwide epidemic, rapidly growing in magnitude with deaths because of overdose and chronic use. A vast majority of these drugs are stimulants that have various effects on the cardiovascular system including the cardiac rhythm. Drugs, like cocaine and methamphetamine, have measured effects on the conduction system and through several direct and indirect pathways, utilizing multiple second messenger systems, change the structural and electrical substrate of the heart, thereby promoting cardiac dysrhythmias. Substituted amphetamines and cocaine affect the expression and activation kinetics of multiple ion channels and calcium signaling proteins resulting in EKG changes, and atrial and ventricular brady and tachyarrhythmias. Preexisting conditions cause substrate changes in the heart, which decrease the threshold for such drug-induced cardiac arrhythmias. The treatment of cardiac arrhythmias in patients who take drugs of abuse may be specialized and will require an understanding of the unique underlying mechanisms and necessitates a multidisciplinary approach. The use of primary or secondary prevention defibrillators in drug abusers with chronic systolic heart failure is both sensitive and controversial. This review provides a broad overview of cardiac arrhythmias associated with stimulant substance abuse and their management.

An optical sensor for the detection and quantification of lidocaine in cocaine samples

An optical sensor (OS) was synthesized by mixing 10,12-pentacosadiinoic acid (PDA) with a triblock copolymer for use in the detection/quantification of lidocaine (LD) in seized cocaine hydrochloride (seized CH) samples. In the presence of LD, the OS presented a chromatic transition from blue to red, while no chromatic transition was observed for other typical cocaine adulterants or cocaine hydrochloride. Isothermal titration calorimetry analysis revealed specific interactions between the PDA molecules of the OS and the LD molecules, with these interactions being enthalpically favorable (-1.20 to -36.7 kJ mol^-1). Therefore, the OS color change only occurred when LD was present in the sample, making the OS selective for LD. Consequently, LD was successfully detected in seized CH samples, irrespective of the type of adulteration. The OS was used for the quantification of LD in seized CH samples containing different adulterants, providing a linear range of 0.0959 to 0.225% (w/w), a precision of 7.2%, an accuracy ranging from -10 to 10%, and limits of detection and quantification of 0.0110% (w/w) and 0.0334% (w/w), respectively.

Multi-drug cocktails: Impurities in commonly used illicit drugs seized by police in Queensland, Australia

BACKGROUND

Impurities in commonly used illicit drugs raise concerns for unwitting consumers when pharmacologically active adulterants, especially new psychoactive substances (NPS), are used. This study examines impurities detected in illicit drugs seized in one Australian jurisdiction.

METHODS

Queensland Health Forensic and Scientific Services provided analytical data. Data described the chemical composition of 9346 samples of 11 illicit drugs seized by police during 2015-2016. Impurities present in primary drugs were summarized and tabulated. A systematic search for published evidence reporting similar analyses was conducted.

RESULTS

Methamphetamine was the primary drug in 6608 samples, followed by MDMA (1232 samples) and cocaine (516 samples). Purity of primary drugs ranged from ∼30% for cocaine, 2-CB and GHB to >90% for THC, methamphetamine, heroin and MDMA. Methamphetamine and MDMA contained the largest variety of impurities: 22 and 18 variants, respectively. Drug adulteration patterns were broadly similar to those found elsewhere, including NPS, but in some primary drugs impurities were found which had not been reported elsewhere. Psychostimulants were adulterated with each other. Levamisole was a common impurity in cocaine. Psychedelics were adulterated with methamphetamine and NPS. Opioids were quite pure, but some samples contained methamphetamine and synthetic opioids.

CONCLUSIONS

Impurities detected were mostly pharmacologically active adulterants probably added to enhance desired effects or for active bulking. Given the designer nature of these drug cocktails, the effects of the adulterated drugs on users from possible complex multi-drug interactions is unpredictable. Awareness-raising among users, research into complex multi-drug effects and ongoing monitoring is required.

Cocaine-Associated Myocardial Infarction

Myocardial ischaemia and infarction has become a well-recognized sequelae of cocaine use. The possibility of recent cocaine use should be assessed in patients with potential myocardial ischaemia because the treatment of patients with myocardial ischaemia related to cocaine differs from that of patients with myocardial ischaemia unrelated to cocaine. Patients with cocaine-associated myocardial ischaemia should receive initial treatment with benzodiazepines to decrease central adrenergic stimulation. Aspirin should be used to reduce thrombus formation, and nitroglycerin to reverse coronary vasoconstriction. Patients with continued ischaemia can be treated with either low doses of phentolamine, or verapamil. If ischaemia continues after treatment with these agents mechanical reperfusion or thrombolytic therapy should be considered depending upon the clinical circumstances. Patients with myocardial ischaemia secondary to cocaine should not receive treatment with beta adrenergic antagonists as these agents enhance coronary vasoconstriction thereby worsening ischaemia.

Analysis of cocaine adulterants in human brain in cases of drug-related death

For different reasons, street cocaine is often diluted with pharmacologically active substances, the so-called adulterants such as levamisole or hydroxyzine. A controversial debate exists currently on the uptake of adulterants from cocaine preparations and drug-related death. Previous research convincingly argues that serious adverse side effects that affect the central nervous and cardiovascular systems can be a consequence of adulterated cocaine.

AIMS

Having identified the presence of adulterants in lung tissue and blood, the concentrations of these substances in brain, an important target location, was of interest. This provides an opportunity to assess their role in cases of drug-related deaths.

MATERIALS AND METHODS

We developed and validated a method for the analysis of cocaine, two cocaine metabolites and six adulterants, which can typically be found in cocaine preparations, and one adulterant metabolite in brain tissue by gas chromatography-mass spectrometry (GC-MS)¹. Ten brain samples which were tested positive for cocaine were analyzed. The homogenized brain tissue was embedded into drying paper for protein precipitation. During a subsequent solid-phase extraction (SPE), the eluate and one of the wash fractions were collected. After derivatization with N-Methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) in pyridine and isooctane, the extracts were analyzed by GC-MS.

RESULTS AND DISCUSSION

The method was fully validated for cocaine (COC), benzoylecgonine (BZE), ecgonine methyl ester (EME), diltiazem (DIL), hydroxyzine (HYD), and levamisole (LEV) and partly validated for cetirizine (CET), lidocaine (LID), phenacetin (PHE), and procaine (PRO) in brain material. By analyzing post-mortem brain tissue of ten cocaine users, LEV, LID, and HYD as well as PHE were identified in contrast to DIL, PRO, and the HYD metabolite CET. HYD and LEV were found in moderate to high concentrations in some cases. Therefore, it cannot be excluded that they have caused adverse side effects.

CONCLUSION

Because adulterants can potentially affect the central nervous and cardiac systems, it is likely that they enhance COC toxicity.

Radiofrequency ablation of drug refractory ventricular tachycardia related to cocaine use: a feasibility, safety, and efficacy study

BACKGROUND

Cocaine use is a known but rare cause of cardiac arrhythmias. Ventricular arrhythmias related to cocaine may not respond to antiarrhythmic drugs and may need treatment with radiofrequency ablation.

OBJECTIVES

We describe the clinical and electrophysiological characteristics of cocaine-related ventricular tachycardia (VT) from a multicenter registry.

METHODS

Subjects presenting with VT related to cocaine use and being considered for radiofrequency ablation have been included in the study. Patients who were refractory to maximal medical therapy underwent radiofrequency ablation of the VT. Clinical, procedural variables, efficacy, and safety outcomes were assessed.

RESULTS

A total of 14 subjects met study criteria (age 44 ± 13, range 18- to 68-year-old with 79% male, 71% Caucasian). MRI showed evidence of scar only in 43% of patients (6/14). The mechanism of VT was focal in 50% (n = 7) and scar related reentry in 50% (n = 7) based on 3D mapping. The mean VT cycle length was 429 ± 96 milliseconds. The site of origin was epicardial in 16% (3/18) of VTs. Most clinical VTs were hemodynamically stable (75%). Mean ejection fraction at the time of admission was 44 ± 14%. Duration of procedure was 289 ± 50 minutes. One subject developed pericardial tamponade requiring drainage. At 18 ± 11 months follow-up, freedom from arrhythmia was seen in 86% (1 case lost to follow-up and 2 died).

CONCLUSION

Radiofrequency ablation is not only feasible but also safe and effective in patients who have drug refractory VT related to chronic cocaine use.

Treatment of patients with cocaine-induced arrhythmias: bringing the bench to the bedside

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.

Toxin-related seizures

Toxin-related seizures result from an imbalance in the brain's equilibrium of excitation-inhibition. Fortunately, most toxin-related seizures respond to standard therapy using benzodiazepines. However, a few alterations in the standard approach are recommended to ensure optimal care and expedient termination of seizure activity. If 2 doses of a benzodiazepine do not terminate the seizure activity, a therapeutic dose of pyridoxine (5 g intravenously in an adult and 70 mg/kg intravenously in a child) should be considered. Phenytoin should be avoided because it is ineffective for many toxin-induced seizures and is potentially harmful when used to treat seizures induced by theophylline or cyclic antidepressants.

Composition, purity and perceived quality of street cocaine in France

BACKGROUND

There is little knowledge about the composition and cocaine content of street cocaine, nor about what users know about it.

METHOD

373 cocaine users were face to face interviewed between May and December 2006 about the last sample of cocaine they had consumed and residual amounts of the substances actually used were analysed using gas phase chromatography coupled to mass spectrometry (GC-MS). Users rated the perceived quality of their product ("good", "average", "poor"), its "estimated percentage of cocaine" and any cutting agents it contained. Price, quantity, place of purchase (street, dealer's premise, appointment), mode of administration (sniffing, injection, smoking) and the supposed nature of the sample (natural, synthetic, no distinction ever made) were also reported. Perceived quality was modelled using multivariate multinomial regression.

RESULTS

The median cocaine content was 22%. Altogether, 343 samples contained cocaine, among which 75% contained at least one adulterant. The most frequently occurring were phenacetin (54% of the samples), caffeine (17%), paracetamol (14%), diltiazem and lidocaïne (11%). Users showed relatively poor discrimination concerning cocaine purity, and only 12% reported at least one of the detected adulterants. The major determinants of their perception of cocaine quality were: place of purchase, natural origin, price per gram, actual cocaine content and mode of administration.

CONCLUSION

The composition of street cocaine is largely unknown to users. Users' perceptions of cocaine quality are based partly on false beliefs and certain administration modes. This may contribute to favouring very risky practices. The effects of adulterants on users' health should be investigated.

Case files of the medical toxicology fellowship at the toxikon consortium in Chicago: cocaine-associated wide-complex dysrhythmias and cardiac arrest - treatment nuances and controversies

A 19-year-old woman was brought by ambulance to the emergency department (ED) from a police holding cell. Less than 3 hours earlier, the patient had been a passenger in a car stopped for a traffic violation. As the police officer approached the car, the patient was noted to hurriedly stuff 2 plastic bags containing a white powdery substance into her mouth. On questioning, it was reported that the packets contained cocaine. Less than an hour after being taken to the police station, the patient was witnessed to have a generalized seizure. What is the pharmacological basis of acute cocaine intoxication? What are the cardiovascular manifestations of acute cocaine intoxication? What is the basis for using sodium bicarbonate in cocaine-induced wide-complex dysrhythmias? What is the basis for the use of lidocaine in cocaine-induced wide-complex dysrhythmias? Is there any evidence for the use of amiodarone to treat cocaine-induced wide-complex dysrhythmias?

Chemically Induced Seizures

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.

Evaluation and Management of the Patient Who Has Cocaine-associated Chest Pain

Patients who have chest pain following the use of cocaine have become more common in emergency departments throughout the United States,with approximately 6% of these patients sustaining an acute MI. The authors have described the rationale for recommending aspirin, benzodiaze-pines, and nitroglycerin as first-line treatments and calcium-channel blockade or phentolamine as possible second-line therapies and have summarized the controversies surrounding the use of fibrinolytic agents. Admission for observation is one reasonable approach to the management of the low-risk cohort. Evaluation for underlying coronary artery disease is reasonable, particularly in patients who have acute MI. Patients who do not have infarction can undergo evaluation for possible coronary artery disease on an outpatient basis. Routine interventions for secondary prophylaxis as well as cocaine rehabilitation should be used in this patient population, because the long-term prognosis seems somewhat dependent upon the ability of the patient to discontinue cocaine use.

The effect of amiodarone pretreatment on survival of mice with cocaine toxicity

INTRODUCTION

Cocaine is a common drug of abuse and use has been associated with ventricular dysrhythmias. Published guidelines suggest that amiodarone is the first line antidysrhythmic for ventricular tachycardia and fibrillation. However, the effects amiodarone in the setting of cocaine toxicity are unknown and unstudied. The purpose of this study was to evaluate the safety and efficacy of amiodarone pretreatment in a murine model of acute cocaine toxicity.

METHODS

This was a randomized, blinded, placebo controlled investigation using male CF-1 mice weighing 29-37 g. First, the safety of an intraperitoneal dose of amiodarone (40 mg/kg) was confirmed in 5 mice. Second, based on preliminary investigations, an approximate intraperitoneal LD50 dose of cocaine (110 mg/kg) was identified and used as the cocaine dose in this study. Animals were then randomized to 2 groups. The control group received 0.5 mL of intraperitoneal 0.9% saline 30 minutes before cocaine. The study group received 40 mg/kg of intraperitoneal amiodarone (40 mg/kg) 30 minutes before cocaine. A blinded observer monitored mice for 2 hours after cocaine administration.

RESULTS

No mice in the amiodarone-only group developed any signs of toxicity or died. In the saline + cocaine group 31/32 (96.9%; 95% CI 83.8 to 99.9) mice seized with a median time to seizure of 2.5 minutes, and 23/32 (71.9%; 95% CI 52.3 to 86.3) died with a median time to death of 5.5 minutes. In the amiodarone + cocaine group 31/33 (93.9%; 95% CI 79.0 to 99.3) mice seized with a median time to seizure of 2.0 minutes, and 24/33 (72.7%; 95% CI 54.5 to 86.7) died with a median time to death of 6.0 minutes. All animals that died did so within 9 minutes. The difference in the proportion of animals dying in the amiodarone + cocaine group compared to the saline + cocaine group was 0.008 (-21 to 22%).

CONCLUSIONS

In this study, pretreatment with amiodarone in cocaine poisoned mice resulted in no change in seizure incidenceor mortality. However, definite conclusions about the reason for these findings cannot be drawn from this model.

Cocaine-associated chest pain

Current estimates establish that more than 30 million people in the United States use cocaine. Cardiovascular complaints commonly occur among patients who present to emergency departments(EDs) after cocaine use, with chest pain the most common complaint in several studies. Although myocardial ischemia and infarction account for only a small percentage of cocaine-associated chest-pain, physicians must understand the pathophysiology of cocaine and appropriate diagnostic and treatment strategies to best manage these patients and minimize adverse outcomes. This article reviews the pharmacology of cocaine, its role in the pathogenesis of chest pain with specific emphasis on inducing myocardial ischemia and infarction, and current diagnostic and management strategies for cocaine-associated chest pain encountered in the ED.

Drug- and toxin-associated seizures

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.

COCAINE USE AND ACUTE MYOCARDIAL INFARCTION

Cocaine use in the United States is widespread, affecting more than 30 million Americans. Although many of these persons do not seek healthcare, the overriding cause for hospitalization is cocaine-associated chest pain. Because only a minority of these patients suffer myocardial injury, it is important to exclude even rarer life-threatening causes for chest pain, such as aortic dissection or pneumothorax. Following that, a thorough knowledge of the pathophysiology and existing literature helps to provide cost-effective care, which focuses resources on those patients most likely to suffer complications. Regardless of the severity of complications, referral to cocaine detoxification programs, counseling, social support, and outpatient follow-up care for modification of cardiac risk factors is a fundamental component of long-term patient care.

The etiology of cardiac arrest in children and young adults: special considerations for ED management

Children and young adults rarely present to the emergency department (ED) in cardiac arrest. This review examines published series on nontraumatic, cardiac arrest for patients aged 1 to 45 years and discusses the differential diagnosis for cardiovascular collapse. Among the most common entities encountered are cardiac diseases (hypertrophic cardiomyopathy, myocarditis), airway diseases (pneumonia, epiglottitis, and asthma), epilepsy, hemorrhage (gastrointestinal bleeding, ectopic pregnancy), and drug toxicity (tricyclic antidepressants, cocaine). ED management of children and young adults in cardiac arrest requires an understanding of the heterogeneous pathophysiologic mechanisms and etiologies leading to cardiopulmonary dysfunction in these patients. The emergency physician should give particular focus to airway management for toddlers and preadolescents, because respiratory diseases predominate. When treating an adolescent or young adult, the resuscitation team should also consider toxic causes as well as occult hemorrhage. Management considerations unique to this patient population are discussed.

Cocaine and lidocaine have additive inhibitory effects on the GABAA current of acutely dissociated hippocampal pyramidal neurons

Inhibition mediated by gamma-aminobutyric acid (GABA) is a major target for the central actions of cocaine and lidocaine, which can result in seizures, especially when these drugs are abused in combination. In the present study, we investigated how cocaine and lidocaine interact to depress GABA current (IGABA), recorded by the whole-cell technique in freshly isolated rat hippocampal neurons. Cocaine depressed IGABA in a concentration dependent manner, such that cocaine was more potent against lower than higher GABA concentrations: the cocaine IC50 was 0.13, 0.62 and 1.2 mM for GABA at 2, 10 and 100 microM, respectively. Cocaine depressed IGABA to the same extent in the absence and presence of 1 microM tetrodotoxin, indicating that cocaine inhibition of IGABA is distinct from its Na+ channel blocking action. Lidocaine reversibly depressed IGABA evoked by 10 microM GABA, with an IC50 of 9.8 mM. In the presence of 3 mM lidocaine, 0.3 mM cocaine depressed IGABA (10 microM GABA) to 30+/-7%. The significantly greater depression by the combined agents (p<0.05) indicates additive effects on the GABA receptor/channel complex, which are likely to contribute to the additive convulsant effects noted when these drugs are abused in combination.

Evaluation of patients with chest pain after cocaine use

Cocaine remains the most common cause of illicit drug-related visits to emergency departments, 40% of which result from chest pain. It is estimated that over half of the 64,000 patients evaluated annually for cocaine-associated chest pain will be admitted to hospitals for the evaluation of myocardial ischemia or infarction, at a health care cost of over eighty million dollars. Although the link between cocaine use and myocardial ischemia is well established, only about 6% of patients with cocaine-associated chest pain will demonstrate biochemical evidence of myocardial infarction. This article focuses on the evaluation of patients with chest pain following cocaine use, and concentrates on ways to improve diagnosis, management, and utilization of health care services.

Decreased cocaine- and lidocaine-induced seizure response by dextromethorphan and DNQX in rat

The present study investigated the effect of dextromethorphan and 6,7-dinitroquinoxaline-2,3-dione (DNQX) pre-treatment on the development of cocaine- and lidocaine-induced seizures. The dopaminergic action of cocaine was also studied. The NMDA antagonist dextromethorphan and the non-NMDA (AMPA/kainate) antagonist DNQX both significantly decreased the intensity of the seizure response to intravenous convulsant doses of cocaine and lidocaine individually (20 mg/kg) and in combination (5 mg/kg each). The incidence of seizures in rats receiving cocaine or lidocaine individually was significantly reduced by pre-treatment with dextromethorphan but not DNQX. Haloperidol did not have an effect on the incidence or intensity of seizures induced by cocaine or lidocaine, alone or in combination. The results suggest that local anesthetic-induced convulsive seizures are mediated by excitatory glutamate transmission through both NMDA and non-NMDA receptor systems.

Cocaine-induced wide complex dysrhythmia

Cocaine is a local anesthetic with the potential to induce dysrhythmia due to direct myocardial sodium channel antagonism similar to class I antidysrhythmic drugs. The hallmark of myocardial sodium channel poisoning is wide complex dysrhythmia, and the current accepted treatment is intravenous bicarbonate. Wide complex dysrhythmio due to cocaine in the absence of myocardial infarction is rare, and optimum management is undefined. We report three cases of acute cocaine intoxicating during which patients developed wide complex dysrhythmia consistent with sodium channel poisoning. In one case, wide complex tachycardia resolved without direct treatment. In the other cases, wide complex dysrhythmia resolved following intravenous bicarbonate therapy directed at reversing sodium channel blockade.

Cocaine and lidocaine in combination are synergistic convulsants

The abuse of cocaine has dramatically increased in the recent decade. Cocaine obtained on the illegal market is rarely found in pure form. Most often it is adulterated with various substances, especially other local anesthetics. Lidocaine is one of the most common local anesthetics employed for adulteration of illicit cocaine. Toxicity due to the simultaneous ingestion of cocaine and lidocaine has been reported. Acute toxicity to cocaine and other local anesthetics is manifested in central nervous system aberrations, such as seizures and convulsions. This study investigated the convulsant potency of cocaine and lidocaine alone and in combination. Rats were administered intravenous injections of 5 mg/kg or 20 mg/kg of cocaine or lidocaine alone and in combination in equal proportion. Seizure activity and intensity were evaluated. The plasma concentration and brain content of each agent was also determined at the time of toxicity. The administration of 5 mg/kg of each drug alone did not yield seizure activity. However, the concomitant administration of 5 mg/kg of both cocaine and lidocaine produced a seizure response nearly equal to that produced after administration of 20 mg/kg of cocaine alone. Diazepam pre-treatment successfully antagonized the seizures induced by cocaine and lidocaine and raised the seizure threshold dose for the combination treatment by approximately four fold. The results suggest that cocaine and lidocaine interact synergistically to increase seizure activity and that the nature of this response occurs in part through a depression of inhibitory neuronal transmission.

Clinical safety of lidocaine in patients with cocaine-associated myocardial infarction

STUDY OBJECTIVE

To evaluate the safety of lidocaine in the setting of cocaine-induced myocardial infarction (MI).

DESIGN

A retrospective, multicenter study.

SETTING

Twenty-nine university, university-affiliated, or community hospitals during a 6-year period (total of 117 cumulative hospital-years).

PARTICIPANTS

Patients with cocaine-associated MI who received lidocaine in the emergency department.

RESULTS

Of 29 patients who received lidocaine in the setting of cocaine-associated MI, no patient died; exhibited bradydysrhythmias, ventricular tachycardia, or ventricular fibrillation; or experienced seizures after administration of lidocaine (95% confidence interval, 0% to 11%).

CONCLUSION

Despite theoretical concerns that lidocaine may enhance cocaine toxicity, the use of lidocaine in patients with cocaine-associated MI was not associated with significant cardiovascular or central nervous system toxicity.

Cocaine-induced myocardial infarction: treatment with thrombolytic therapy

Patients with cocaine-induced AMI may be added to the expanding list of eligible candidates for thrombolytic therapy. ED nurses are in key positions to identify patients for thrombolysis, evaluate patients' responses, and minimize complications. With the rising use of cocaine, increased consideration should be given to any relatively young patient with unexplained cardiovascular symptoms and history of cocaine use.

The effects of lidocaine pretreatment on cocaine neurotoxicity and lethality in mice

OBJECTIVE

To evaluate the effects of an antiarrhythmic dose of lidocaine on cocaine-induced ataxia, seizures, and death in mice.

METHODS

A randomized, controlled, blinded investigation was conducted using 220 female Swiss albino mice. Groups of 20 animals received intraperitoneal (IP) administration of either 31.6 mg/kg of lidocaine hydrochloride in 0.9% NaCl (ten animals) or an equal volume of 0.9% NaCl solution (ten animals). After 5 minutes, all the animals received IP cocaine in incremental doses ranging from 40 to 110 mg/kg. The animals were observed for ataxia, seizures, and death. The animals pretreated with lidocaine were compared with the control animals for the number of adverse effects from cocaine at each dose tested.

RESULTS

Lidocaine significantly increased the overall incidences of cocaine-induced ataxia (p = 0.02) and seizures (p < 0.001). However, pretreatment with lidocaine offered protection against cocaine lethality (p < 0.0001).

CONCLUSION

In this preexposure model, lidocaine protects mice against cocaine-induced lethality. These effects seem to be independent of convulsive activity. Further study is required to determine the safety and efficacy of lidocaine for the management of cocaine-induced arrhythmias.

Hyperthermia in psychostimulant overdose

Psychostimulant drugs such as amphetamines, amphetamine derivatives, and cocaine produce a variety of potentially lethal effects, and an understanding of these toxic effects is important for emergency physicians. While some effects of psychostimulant poisonings such as cardiovascular compromise and seizures have been discussed extensively, other metabolic derangements such as hyperthermia are less well characterized. In fact, hyperthermia is a common feature of severe-to-lethal poisonings and may be the primary mode of demise in some patients. Animal studies confirm that drug-induced hyperthermia alone can be lethal in some species, although other toxic effects may predominate at different drug doses or rates of administration. In non-lethal poisonings, hyperthermia can produce rhabdomyolysis, leading to further morbidity. Clinical reports and animal studies indicate that hyperthermia is a primary effect of psychostimulant drugs and can occur independently of seizures or increased motor activity. Furthermore, activation of particular dopamine receptors in the central nervous system appears to mediate psychostimulant-induced hyperthermia. The literature suggests cooling and tranquilization of psychostimulant-poisoned patients after cardiovascular stabilization. Paralysis and mechanical ventilation may be required. The involvement of dopamine receptor activation in psychostimulant toxicity suggests that dopamine-blocking neuroleptic drugs may be a useful adjunct to current treatment regimens. However, further studies are required to assess this approach. In summary, hyperthermia is a potentially lethal but treatable manifestation of severe psychostimulant poisoning.

Cocaine toxicity and the calcium channel blockers nifedipine and nimodipine in rats

Two dihydropyridine type calcium channel blockers (CCBs) were studied for any protective or therapeutic effect upon cocaine-induced toxicity and death in rats. To test for the protective effects, rats were pretreated with vehicle (control), nifedipine or nimodipine, intraperitoneally (IP) 30 minutes prior to an LD85 of cocaine, or intravenously (IV) 10 minutes prior to cocaine administration. Animals receiving IP control vehicle developed seizures in 5.6 +/- 1.0 minutes and respiratory arrest in 9.8 +/- 1.4 minutes. Animals pretreated IP with nifedipine or nimodipine developed seizures and respiratory arrest significantly sooner than the controls, although the overall incidences of seizures and respiratory arrest were not significantly different. Pretreatment with IV CCBs resulted in similar findings. To test the therapeutic effect of CCBs given following cocaine overdose, rats were administered cocaine IP and then treated with IV nifedipine or nimodipine once seizures occurred. In these animals, there was no significant difference in the incidence or time to respiratory arrest compared to vehicle controls. This study demonstrates that neither pretreatment nor posttreatment with the CCBs nifedipine or nimodipine reduces cocaine toxicity in this rodent model.

Tetracaine protects against cocaine lethality in mice

STUDY HYPOTHESIS

Tetracaine will enhance cocaine toxicity.

STUDY POPULATION

Two hundred forty female Swiss albino mice weighing 27 to 45 g.

METHODS

Intraperitoneal injections of tetracaine and cocaine were given to groups of ten mice each in a controlled, blinded fashion. Either tetracaine or an equal volume of normal saline was given five minutes before one of six incremental doses of cocaine, ranging from 60 to 110 mg/kg. The experiment was repeated twice using two different doses of tetracaine: either an LD10 (40 mg/kg determined from preliminary studies), or one-twentieth of the dose of cocaine (which approximates the ratio used in tetracaine, epinephrine, and cocaine). Lethality was recorded at 24 hours. Lethality between groups was compared with a Wilcoxon sign-rank test.

RESULTS

Tetracaine reduced cocaine lethality at all doses. This reduction in lethality was statistically significant at both tetracaine doses (P < .05).

CONCLUSION

In the mouse, pretreatment with tetracaine significantly decreases cocaine lethality.

Refractory status epilepticus in adults

The management of status epilepticus has improved over the past 20 years, resulting in a substantial decrease in the associated morbidity and mortality. Patients who have seizures that are refractory to initial pharmacologic interventions tend to have significant underlying toxic, metabolic, structural, or infectious disorders, and therefore management of refractory status epilepticus must focus on stabilization and on identification and correction of seizure etiology. Regardless of etiology, the faster the seizures are brought under control, the better the prognosis. Risk of central nervous system injury increases after 30 minutes of seizure activity, and therefore efforts should focus on controlling the abnormal electrical discharges at the earliest time possible, preferably within one hour. Benzodiazepines, phenytoin, and phenobarbital remain the most commonly used first- and second-line anticonvulsants, have proven effective in cases of status epilepticus, and should be administered within the first 45 minutes of management. For refractory status epilepticus, pentobarbital anesthesia is evolving as an effective and recommended treatment modality and should be instituted immediately after phenytoin and phenobarbital loading. The role of other anticonvulsants remains to be investigated in controlled clinical trials.

Potentiation of cocaine and d-amphetamine toxicity with caffeine

The effect of caffeine when combined with cocaine or amphetamine was studied in rats. Animals were pretreated with intraperitoneal vehicle (normal saline [NS]) or caffeine 100 mg/kg, then challenged with intraperitoneal cocaine (0, 35, 50, 70, or 90 mg/kg) or intraperitoneal d-amphetamine (0, 15, 25, 35, or 42 mg/kg). Animal behavior, time to, and incidences of seizures and death were recorded. This dose of caffeine alone did not cause seizures or death. Caffeine pretreatment significantly increased the incidence of overt seizures induced by either cocaine or amphetamine. Caffeine increased the incidence of cocaine-induced death from 10% to 90% at the 70 mg/kg cocaine dose (P less than .01). Caffeine increased amphetamine-induced death from 0% to 80% at 15 mg/kg (P less than or equal to .01), 10% to 70% at 25 mg/kg (P less than or equal to .01), and 30% to 80% at 35 mg/kg (P less than or equal to .01). To investigate mechanisms, additional animals were pretreated with the adenosine agonist, 2-chloroadenosine (2.5 and 10 mg/kg), before being challenged with NS, 90 mg/kg cocaine, or 42 mg/kg amphetamine. Pretreatment with 2-chloroadenosine had no affect in reducing cocaine or amphetamine toxicity. Combination pretreatment with caffeine and 2-chloroadenosine potentiated cocaine toxicity. The phosphodiesterase inhibitor, pentoxifylline, did not potentiate cocaine toxicity. The authors conclude that caffeine potentiates the acute toxicity of both cocaine and amphetamine, and that the failure of 2-chloroadenosine to alter this suggests that the toxicity of the stimulants cocaine and amphetamine may be modulated by nonspecific rather than specific adenosine- or phosphodiesterase-induced mechanisms.

Cocaine-induced myocardial infarction: an analysis and review of the literature

The objectives of this paper are to analyze the case reports of cocaine-induced myocardial infarction and to better define the clinical characteristics of this syndrome. An English language literature search was carried out using MEDLINE, and a bibliographic review of all identified articles and book chapters was conducted. Ninety-one cases of cocaine-induced myocardial infarction were identified. Intranasal, intravenous, and inhalational routes of abuse all resulted in myocardial infarction. Fourty-four percent of patients had previously noted chest pain. Eighty-seven percent of patients were cigarette smokers. Two-thirds of patients had their myocardial infarction within 3 hours of the use of cocaine (with a range of 1 minute to 4 days). Cardiac catheterizations were abnormal in 30 of 54 patients (55%). Of the 24 patients with reported follow-up, 14 (58%) had further ischemic events after discharge. In conclusion, cocaine-induced myocardial infarction identifies a group of young individuals who may be prone to recurrent complications after initial presentation.