Treatment of toad venom poisoning with digoxin-specific Fab fragments

Animal-derived natural products for hepatocellular carcinoma therapy: current evidence and future perspectives

Hepatocellular carcinoma (HCC) has a high morbidity and mortality rate, and the survival rate of HCC patients remains low. Animal medicines have been used as potential therapeutic tools throughout the long history due to their different structures of biologically active substances with high affinity to the human body. Here, we focus on the effects and the mechanism of action of animal-derived natural products against HCC, which were searched in databases encompassing Web of Science, PubMed, Embase, Science Direct, Springer Link, and EBSCO. A total of 24 natural products from 12 animals were summarized. Our study found that these natural products have potent anti-hepatocellular carcinoma effects. The mechanism of action involving apoptosis induction, autophagy induction, anti-proliferation, anti-migration, and anti-drug resistance via phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), Ras/extracellular signal regulated kinases (ERK)/mitogen-activated protein kinase (MAPK), Wnt/β-catenin, and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways. Huachansu injection and sodium cantharidate have been used in clinical applications with good efficacy. We review the potential of animal-derived natural products and their derivatives in the treatment of HCC to date and summarize their application prospect and toxic side effects, hoping to provide a reference for drug development for HCC.

2023 American Heart Association Focused Update on the Management of Patients With Cardiac Arrest or Life-Threatening Toxicity Due to Poisoning: An Update to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

In this focused update, the American Heart Association provides updated guidance for resuscitation of patients with cardiac arrest, respiratory arrest, and refractory shock due to poisoning. Based on structured evidence reviews, guidelines are provided for the treatment of critical poisoning from benzodiazepines, β-adrenergic receptor antagonists (also known as β-blockers), L-type calcium channel antagonists (commonly called calcium channel blockers), cocaine, cyanide, digoxin and related cardiac glycosides, local anesthetics, methemoglobinemia, opioids, organophosphates and carbamates, sodium channel antagonists (also called sodium channel blockers), and sympathomimetics. Recommendations are also provided for the use of venoarterial extracorporeal membrane oxygenation. These guidelines discuss the role of atropine, benzodiazepines, calcium, digoxin-specific immune antibody fragments, electrical pacing, flumazenil, glucagon, hemodialysis, hydroxocobalamin, hyperbaric oxygen, insulin, intravenous lipid emulsion, lidocaine, methylene blue, naloxone, pralidoxime, sodium bicarbonate, sodium nitrite, sodium thiosulfate, vasodilators, and vasopressors for the management of specific critical poisonings.

Life-threatening pediatric poisoning due to ingestion of Bufo bufo toad eggs: A case report

Bufo parotid glands and eggs contain cardiac glycosides also known as bufadienolides. This class of molecules can cause digoxin-like cardiac toxicity, as they can block the sodium potassium-adenosine triphosphatase (Na/K-ATPase) pump. Poisoning with these toxins is rare but carries a high mortality risk. There are only a few cases of toad poisoning that have been reported worldwide, mainly in the southern hemisphere. We will describe the case of a child on the autistic spectrum disorder who developed an acute and severe cardiac bradyarrhythmia soon after being in a mountain creek. The child ingested a large quantity of Bufo bufo toad eggs and developed bradycardia (35/min) associated with junctional rhythm with narrow QRS complexes. The poison control center (PCC) indicated the use of atropine on the way to the nearest hospital and the administration of antidotal therapy, i.e., anti-digoxine fragment antibodies (DigiFab), as soon as possible. The patient was transferred by air ambulance to the Regional Referral Pediatric Hospital (RRPH), tested for digoxin blood level by immuno-essay (0.68 ng/mL) and successfully treated with five vials of DigiFab, since atropine administration produced only a fleeting effect on the cardiac rhythm. Patient was discharged 48 hours after poisoning. The presence of bufadienolides in the toad eggs was also confirmed. To our knowledge, this is the first report of toad egg poisoning in Europe. The administration of Digifab helped to reverse the bufadienolide cardiac toxicity.

Case Report: Clinical Presentation of Toad Venom-Induced Cardiac Intoxication

Six people made the mistake of eating toad soup, and one of them died before arriving hospital. Five patients presented conscious change, gastrointestinal upset, or bradycardia. We checked their blood and electrocardiography to monitor the cardiac intoxication from toad venom. This experience revealed that the serum level of digoxin does not indicate the severity of intoxication but has the diagnostic value. And, serum potassium level is useful to provide valuable therapeutic information.

Ayahuasca, a potentially rapid acting antidepressant: focus on safety and tolerability

INTRODUCTION

Ayahuasca is a psychedelic brew originally used by indigenous tribes from the Amazon Rainforest and in religious rituals. Pre-clinical and observational studies have demonstrated its possible potential as an antidepressant, and open and placebo-controlled clinical trials corroborated these results. For it to become an approved treatment for depression, its safety and tolerability need to be assessed and documented.

AREAS COVERED

We have gathered data regarding occurrence of adverse events (AEs) in all reported randomized, placebo-controlled trials with healthy and clinical populations involving ayahuasca administration (n = 108 ayahuasca administrations). We systematically categorized these results, recorded their prevalence and discussed the possible mechanisms related to their emergence.

EXPERT OPINION

: There were no reports of serious AEs, indicating a relative safety of ayahuasca administration in controlled settings. Most common AEs related to ayahuasca administration included nausea, vomiting, headaches and transient increases in cardiovascular measurements. Ayahuasca research is still in its infancy, especially concerning the absence of large and robust clinical trials to verify its antidepressant effects. Dose standardization, legal prohibition of the possession of its alkaloids and how traditional communities will be compensated if ayahuasca becomes an approved medicine are the biggest obstacles to overcome for its future use in the therapeutic context.

An Efficient Method for the Euthanasia of Cane Toads (Rhinella marina) under Northern Australian Field Conditions

Simple Summary

Cane toads are a highly invasive species that present a serious threat to most vertebrates that eat them. In Australia, their spread from the point of introduction in 1935 has seen them occupy any suitable habitat across the north of the country, with the potential to be transported to locations in southern Australia. Control and safe removal of unwanted toads presents ethical and occupational health risks to those engaged in such activities. This study describes an efficient method of control suitable for application under field conditions anywhere in Australia.

Abstract

The euthanasia of cane toads under field conditions presents a number of logistical and animal welfare challenges. One recommended method of control involves the use of carbon dioxide in plastic bags. This paper describes the minimum amount of time (4 h) required to efficiently euthanase toads with a carbon dioxide concentration of 4.96% under field conditions experienced in northern Australia. Discussion is also provided on the issues of safe disposal of biological and plastic waste associated with the application of this method.

Adverse Events Associated with Use of Digoxin Immune Fab Reported to the US Food and Drug Administration Adverse Event Reporting System, 1986-2019

Background

Digoxin immune fab products, DigiBind and DigiFab, are antidotes for the treatment of patients with life-threatening or potentially life-threatening digoxin toxicity or overdose. Although approved by the US Food and Drug Administration (FDA) in 1986 (DigiBind) and 2001 (DigiFab), there remains a paucity of literature describing the safety of these products in the postmarketing setting.

Objective

We sought to assess US adverse event (AE) reports submitted to the FDA Adverse Event Reporting System (FAERS) for DigiBind and DigiFab in the postmarketing period.

Patients and Methods

We searched reports for DigiBind and DigiFab submitted from the time of each product approval through December 31, 2019. Descriptive statistics were used to assess AE reports for DigiBind and DigiFab. Empirical Bayes geometric means (EBGMs) and their 90% confidence intervals were computed to identify disproportionate (i.e., at least twice the expected) reporting of DigiBind and DigiFab. Reports describing selected AEs and death outcomes were individually reviewed.

Results

A total of 78 DigiBind and 43 DigiFab reports were identified, of which 68 DigiBind (87.2%) and 27 DigiFab (62.8%) reports were serious. Among the most frequently reported AEs for both products [DigiBind, DigiFab, respectively] were cardiac (bradycardia [3.8%, 3.9%], cardiac arrest [3.3%, 3.9%], and hypotension [2.4%, 2.6%]) and non-cardiac (nausea [1.9%, 2.6%] and hyperkalemia [1.4%, 1.9%]) events. These AEs were labeled events or confounded by indication for use (digoxin toxicity). Nineteen (24.4%) DigiBind and 13 (30.2%) DigiFab reports described an outcome of death, of which seven (53.8%) DigiFab reports were attributed to poisoning with non-digoxin cardiac glycosides. No deaths could be attributed to DigiBind or DigiFab administration.

Conclusions

Our analysis did not identify new safety concerns for DigiBind or DigiFab. Most AEs reported were labeled events or confounded by indication for use.

Establishment of a High-Resolution Liquid Chromatography-Mass Spectrometry Spectral Library for Screening Toxic Natural Products

Many natural products have biological effects on humans and animals. Poisoning caused by natural products is common in clinical toxicology cases. Liquid chromatography-high-resolution-mass spectrometry (LC-HRMS) has recently emerged as a powerful analytical tool for large-scale target screening, and the application of LC-HRMS can be expanded to evaluate potential natural product poisoning in clinical cases. We report the construction of an LC-HRMS spectral library of 95 natural products commonly implicated in poisoning, and an LC-HRMS assay was validated for definitive detection of natural products in urine and serum samples. For each compound, the limit of detection (LOD) was determined in the analytical range of 1.0 - 1000 ng/mL for urine samples and 0.50 - 500 ng/mL for serum samples. The mean (SD) of matrix effects for urine samples and that for serum samples were both -21% (22%), and the mean (SD) of recovery for serum samples was 89% (26%). The LC-HRMS assay was successfully applied to identify natural products in clinical cases. The spectral library parameters of each compound are provided in the supplementary material to aid other laboratories in identification of unknown natural toxins and development of similar methods on different mass spectrometry platforms.

Toad Poisoning: Clinical Characteristics and Outcomes

Objective

This study was performed to describe the clinical characteristics and outcomes of patients with toad poisoning in Thailand.

Methods

We carried out a retrospective study of patients with toad poisoning from the Ramathibodi Poison Center Toxic Exposure Surveillance System during a 5-year period (2012–2016).

Results

We studied 36 patients poisoned by toad toxin. The median age was 31 years. Most patients were male (66.7%) and had ingested toad meat (50%). The most common presentation was gastrointestinal (GI) symptoms with a median onset of 2 h after ingestion. Twelve patients presented with bradycardia; seven presented with shock and one with cardiac arrest. In the initial EKGs of all patients, the most common abnormality was sinus bradycardia.Two patients developed cardiac arrest early during management in the emergency room (within 15 minutes after ER arrival or within 4.5 h after ingestion). During admission, one patient developed sinus bradycardia, and two developed bradyarrhythmia; however, all three were stable. No tachyarrhythmias such as ventricular tachycardia were detected in any patient. Some patients (11.1%) presented with hyperkalemia. Serum digoxin was detected in five of seven patients tested, ranging from 0.43 to >8 ng/mL. Most patients (75%) were admitted to the hospital; the median duration of hospitalization was 2 d (range 0.5–5 d). The overall mortality rate was 8.3%, and all three patients that died ate toad meat and/or eggs and developed cardiac arrest. All patients received supportive with/without symptomatic care including GI decontamination, inotropic drugs, cardiac pacing, and management of hyperkalemia. One patient received intravenous calcium for hyperkalemia but did not develop dysrhythmia after calcium administration. One patient received digoxin-specific antibody fragments (DsFab), after which he clinically improved and was discharged.

Conclusion

Toad poisoning commonly caused GI symptoms and bradycardia. However, in severe cases, death occurred. Tachyarrhythmia was not observed. Supportive, symptomatic care might be the main therapies for this poisoning, especially if DsFab is not available.

Endogenous Bufadienolides, Fibrosis and Preeclampsia

Frequency of preeclampsia has no tendency to decrease, and it still takes the leading position in the structure of maternal mortality and morbidity worldwide. In this review, we present the “fibrotic concept” of the etiology and pathogenesis of preeclampsia which involves system consisting of Na/K-ATPase and its endogenous ligands including marinobufagenin. New therapy of preeclampsia includes modulation of the Na/K-ATPase system by immunoneutralization of the marinobufagenin and use of mineralocorticoid antagonists which are capable to impair marinobufagenin-Na/K-ATPase interactions.

Bufotoxin poisoning that showed the sign of acute digitalis overdose in the patient of Kyushin® intoxication

Introduction:

Kyushin® is a widely used herbal medicine in East Asia for heart failure. Toad venom in present in Kyushin®, which has positive inotropic effect as digitoxin.

Case presentation:

An 81-year-old, female patient presented with decreased mental status after overdose of Kyushin®. The first electrocardiogram showed junctional tachycardia with 142/min, suddenly dropped to 27/min and followed by ventricular fibrillation. After one cycle of CPR, spontaneous circulation returned but junctional bradycardia, tachycardia, and ventricular fibrillation appeared. After six times of defibrillation, spontaneous circulation returned, and mechanical ventilator and transcutaneous pacing were applied. Plasma toxicology test revealed digitoxin 66.90 ng/mL by cloned enzyme donor immunoassay and digoxin 0.76 ng/mL by kinetic interaction of microparticles in solution immunoassay. After 8 h from presentation, the patient’s mental status came to be alert, and then transcutaneous pacing was removed.

Discussion:

Cloned enzyme donor immunoassay has been reported to be highly cross-reactive with digoxin-like substances, which strongly supports bufotoxin to be responsible for arrhythmia of the patient.

Conclusion:

Poisoning of bufotoxin in Kyushin® can cause cardiac arrhythmia, even arrest, but without digoxin-specific Fab, conventional therapy could be successful.

Comprehensive review of cardiovascular toxicity of drugs and related agents

Cardiovascular diseases are a leading cause of morbidity and mortality in most developed countries of the world. Pharmaceuticals, illicit drugs, and toxins can significantly contribute to the overall cardiovascular burden and thus deserve attention. The present article is a systematic overview of drugs that may induce distinct cardiovascular toxicity. The compounds are classified into agents that have significant effects on the heart, blood vessels, or both. The mechanism(s) of toxic action are discussed and treatment modalities are briefly mentioned in relevant cases. Due to the large number of clinically relevant compounds discussed, this article could be of interest to a broad audience including pharmacologists and toxicologists, pharmacists, physicians, and medicinal chemists. Particular emphasis is given to clinically relevant topics including the cardiovascular toxicity of illicit sympathomimetic drugs (e.g., cocaine, amphetamines, cathinones), drugs that prolong the QT interval, antidysrhythmic drugs, digoxin and other cardioactive steroids, beta-blockers, calcium channel blockers, female hormones, nonsteroidal anti-inflammatory, and anticancer compounds encompassing anthracyclines and novel targeted therapy interfering with the HER2 or the vascular endothelial growth factor pathway.

Digoxin: The Monarch of Cardiac Toxicities

The cardiac steroids (or glycosides) are a heterogeneous group of compounds that have been well recognized for both their clinical benefit and inherent toxicity. This review will primarily focus on digoxin because of its widespread clinical use, although the other cardiac steroids will be discussed in less detail. The cardiac steroids have a narrow therapeutic index and remain a significant source of toxicity, with nearly 5000 human exposures reported to the American Association of Poison Control Centers in 2002. Digoxin reversibly binds to the α subunit of the Na+ -K+ ATPase pump and completely inhibits its enzymatic and transport functions. The cumulative effect on cardiac tissue is dependent on the number of Na+ -K+ ATPase pump sites that are occupied by cardiac steroid molecules. It is important to recall the pharmacokinetics of digoxin in that serum digoxin levels drawn prior to tissue distribution (<6 hours) do not accurately reflect acute toxicity. Signs and symptoms of toxicity vary between acute and chronic intoxications. A systematic approach guided by clinical symptoms with early administration of immunotherapy can lead to a significant reduction of morbidity and mortality in digoxin-poisoned patients.

Toad Intoxication in the Dog by Rhinella marina : The Clinical Syndrome and Current Treatment Recommendations

Oral exposure to the secretions of Rhinella marina (formerly Bufo marinus ) can carry a high fatality rate without early and appropriate treatment. In dogs, the clinical syndrome, which is evident almost immediately, manifests in profuse ptyalism along with gastrointestinal, respiratory, and neurologic signs. Severe cardiac arrhythmias develop less frequently. This review will cover the history, toxicology, and clinical syndrome of Rhinella marina intoxication, and will discuss the recommended therapies for stabilization.

Protective effect of taurine on cardiotoxicity of the bufadienolides derived from toad (Bufo bufo gargarizans Canto) venom in guinea-pigs in vivo and in vitro

In China, toad venom is an anti-inflammatory agent used in small doses for the treatment of various types of inflammation. Bufadienolides are cardioactive steroids responsible for the anti-inflammatory actions of toad venom. We studied the protective effect of taurine on the cardiotoxicity of bufadienolides in guinea-pigs. Bufadienolides (8 mg/kg) caused arrhythmias, cardiac dysfunction and death in guinea-pigs. Pretreatment with taurine (150, 300 mg/kg) significantly prevented bufadienolide-induced cardiotoxicity and reduced the mortality in vivo. Taurine markedly increased the cumulative doses of bufadienolides and resibufogenin required for lethal arrhythmia in ex vivo isolated guinea-pig heart. Taurine did not compromise the anti-inflammatory activity of the bufadienolides on concanavalin-A-stimulated proliferation of guinea-pig splenocytes in vitro. These data indicate that taurine can prevent bufadienolide-induced cardiotoxicity and could be a novel antidote in combination with bufadienolide therapy.

Cardioactive steroid poisoning: a comparison of plant- and animal-derived compounds

INTRODUCTION

Cardioactive steroids (CASs) are found in plants, animals, and insects. Their affinity for Na+-K+ ATPase is attenuated by the type of lactone at carbon 17 (C17) of the steroid backbone: those with 5-membered lactone rings, or cardenolides, are derived mostly from plants with 6-membered rings or from animals with bufadienolides. A systematic review of CAS poisoning was performed to compare the mortality rate of cardenolides and bufadienolides.

METHODS

MEDLINE was searched for articles using commonly reported names of CASs, and keywords were limited to human cases only. We searched cases from 1982 to 2003, so that supportive care was similar and digoxin-specific Fab was available. Identified reports of CAS poisoning were read to exclude cases involving licensed pharmaceuticals. Inclusion criteria included hyperkalemia, gastrointestinal symptoms, electrocardiographic evidence of CAS toxicity, digoxin serum concentration, or history of exposure to a substance containing a CAS. Clinical data was collected, including information about treatment with digoxin-specific Fab and treatment outcome.

RESULTS

Fifty-nine articles, describing 924 patients, were identified. Eight hundred ninety-seven patients (97%) ingested a CAS with a 5-membered lactone ring, and mortality was 6% (n = 54). Twenty-seven patients (2.9%) ingested a CAS with a 6-membered lactone ring, and mortality was 29.6% (n = 8). The difference in mortality rates was statistically significant (p < 0.001, [X2]). CASs with 6-member rings accounted for the highest percentage of nonsuicidal exposures.

CONCLUSION

Although cardenolides accounted for the majority of exposures, bufadienolides were five times more lethal than cardenolides.

Life-threatening episode after ingestion of toad eggs: a case report with literature review

It is known that toad possesses several toxic substances in the skin and parotid glands. In the past, toad-venom poisoning had been reported from ingestion of toad soup, Kyushin and aphrodisiac pills, but the poisoning from toad eggs is observed for the first time. The case of a healthy female who had previously eaten toad soup twice without any discomfort is reported. She developed gastrointestinal symptoms and life-threatening cardiac rhythm after ingestion of toad eggs.

A retrospective report of 90 dogs with suspected cane toad (Bufo marinus) toxicity

OBJECTIVE

To report the clinical characteristics of toad toxicity in domestic dogs in Brisbane.

DESIGN

A retrospective analysis of clinical cases.

PROCEDURE

All cases of toad poisoning which presented to a northern suburbs emergency clinic in Brisbane over a 30-month period beginning in April 1999 were reviewed.

RESULTS

A total of 90 canine cases of suspected toad poisoning were reviewed. Small breed dogs accounted for 76% of cases. Jack Russell, Silky, and Fox Terriers were the most represented breeds. Cases were reported year round, with fewest cases over the winter months. The most common clinical signs were increased salivation (78% of cases), and red oral mucous membranes (63% cases). Seizures occurred in 31% of cases. Generally the outcome was excellent with 96% survival.

Fab antibody fragments: some applications in clinical toxicology

This review provides current information on the use of antigen-binding fragments (Fab) from cleaved antibodies to treat poisoning with digoxin and other potent, low formula mass poisons, such as colchicine and tricyclic antidepressants. Anti-digoxin Fab fragments have been used successfully for many years in the management of severe poisoning with digoxin, digitoxin, and a range of other structurally related compounds, including cardiotoxins from Nerium and Thevetia sp. (oleander) and Bufo sp. (toads). However, their main use remains treating digoxin poisoning. Equimolar doses of anti-digoxin Fab fragments completely bind digoxin in vivo. The approximate dose of Fab fragments (mg) is 80 times the digoxin body burden (mg). If neither the dose ingested nor the plasma digoxin/digitoxin concentration is known, in an adult 380 mg of anti-digoxin Fab fragments should be given. The dose for elderly patients or those with renal impairment should be similar to that for those with normal renal function. Fab fragments have a plasma half-life of 12-20 hours, but this can be prolonged in patients with renal impairment. Analysis of serum ultrafiltrate using an immunoassay shown not to have matrix bias remains the most accurate approach to measuring free digoxin in the presence of anti-digoxin Fab fragments. The antibody fragments are given intravenously over 15-30 minutes after dilution to at least 250 mL with plasma protein solution, 0.9% (w/v) sodium chloride, or deionised water, except in infants where the volume infused can be reduced. Factors limiting the efficacy of Fab fragments are the dose, the duration of the infusion and any delay in administration. Guidelines for Fab fragment administration in children include (i) dilution to a final Fab concentration of 10 g/L in either 5% (w/v) dextrose or 0.9% (w/v) sodium chloride; (ii) infusion through a 0.22 microm filter; (iii) administration of the total dose over a minimum of 30 minutes; and (iv) avoiding coadministration of other drugs and/or electrolyte solutions. Fab fragments are generally well tolerated. Adverse effects attributable to Fab treatment include hypokalaemia and exacerbation of congestive cardiac failure; renal function could be impaired in some patients. Fab fragment preparations for treating acute colchicine and tricyclic antidepressant poisoning have been developed, but are not available commercially. Colchicine poisoning is rare in Western countries, and pharmacological management together with supportive care is usually effective even in severe tricyclic antidepressant overdosage. Attempts have been made to produce anti-paraquat antibodies capable of enhancing paraquat elimination from the lung, but thus far all such attempts have proved unsuccessful.

Plant exposures: wilderness medicine

This article discusses poisonous plants, the symptoms that might arise if they are ingested, and the treatments that should be administered to patients.

Characterization of the neutralizing activity of digoxin-specific Fab toward ouabain-like steroids

Digoxin-specific Fab (Digibind) is a mixture of antidigoxin Fab fragments prepared from sheep sera and is used as a treatment for digoxin poisoning. Digoxin-specific Fab has been shown to neutralize an endogenous Na+/K+ ATPase inhibitor (endogenous digoxin-like Na+/K+ ATPase regulatory factor; EDLF) in rats and humans and to lower blood pressure. Although the exact structure of EDLF is unknown, compounds identical to or structurally related to ouabain, bufalin, and marinobufagenin have been detected in mammalian plasma. In this study, some structural characteristics of EDLF were inferred from the ability of digoxin-specific Fab to neutralize the Na+/K+ ATPase inhibitory activity of several known cardenolides and bufodienolides. Additional structural information was obtained from [3H]ouabain binding and enzyme-linked immunosorbent assay experiments. Digoxin-specific Fab had the ability to interact to some extent with all of the cardenolides and bufodienolides tested. However, digoxin-specific Fab was more than 20-fold more potent in neutralizing ouabain and bufalin than marinobufagenin. The antihypertensive effect of digoxin-specific Fab seen in preeclampsia and animal models of hypertension may therefore be due to a molecule identical to or structurally similar to ouabain or bufalin.

Toad venom poisoning: resemblance to digoxin toxicity and therapeutic implications

A healthy man developed gastrointestinal symptoms after ingesting purported aphrodisiac pills. He had severe unrelenting bradycardia, hyperkalaemia, and acidosis. He rapidly developed severe life threatening cardiac arrhythmias and died after a few hours. He was found to have positive serum digoxin concentrations, although he was not taking digoxin. Toad venom poisoning is similar to digitalis toxicity and carries a high mortality. Cardiac glycoside poisoning can occur from ingestion of various plants and animal toxins, and the venom gland of cane toad (Bufo marinus) contains large quantities of cardiac glycosides. Toad venom, a constituent of an aphrodisiac, was considered responsible for the development of clinical manifestations and death in this patient. Digoxin specific Fab fragment has been reported to be beneficial in the treatment of toad venom poisoning. This report alerts physicians to the need to be aware of a new community toxic exposure, as prompt treatment with digoxin specific Fab fragment may be life saving. The treatment approach to patients with suspected toad venom poisoning is described.

Study on mechanism of action of Chinese medicine Chan Su: dose-dependent biphasic production of nitric oxide in trophoblastic BeWo cells

BACKGROUND

Chan Su, a traditional Chinese medicine, is used for treating the heart diseases and other systemic illnesses. Our studies with animal model have revealed its role in increasing intracellular calcium concentration in cardiomyocytes. Nitric oxide (NO), a second messenger molecule, and its metabolites have been demonstrated to maintain and modulate multiple physiologic functions including the cardiovascular and reproductive systems. In order to explore the mechanism of action of Chan Su, we studied the ability of Chan Su to stimulate NO production in cultured trophoblastic BeWo cells.

MATERIALS AND METHODS

BeWo cell is a cloned established cell line purified from human choriocarcinoma. These cells have some similarities in biological behavior with endothelial cells. Therefore, BeWo cell line may act as a model system for production of nitric oxide by Chan Su both in placenta and in cardiovascular tissue, and the results can easily be extrapolated to cardiomyocytes. Very small amount of ethanol extract of Chan Su was added to the cultured cells in KBM buffer and a chemiluminescence system was used for the measurement of nitric oxide. The amounts of Chan Su extract added to cultured cells were comparable to expected level of Chan Su in human serum after ingestion. We also repeated these experiments with bufalin, the active component of Chan Su.

RESULTS

The ethanol extract of Chan Su (5 and 10 microg/ml) significantly increased NO production up to 110% of basal control value, but higher concentrations (40 and 80 microg/ml) of Chan Su (as expected in an overdose) resulted in decreased NO production below the control level. This biphasic effect on nitric oxide production was also observed with bufalin, the active component of Chan Su responsible for its digoxin-like immunoreactivity. The presence of bufalin in Chan Su preparation was confirmed by thin layer chromatography (TLC) analysis.

CONCLUSIONS

Chan Su as well as bufalin is able to modulate the production of NO in BeWo cell line.

Cardioactive steroid poisoning from an herbal cleansing preparation

We describe a case of unintentional poisoning from a cardioactive steroid and the subsequent analytic investigation. A 36-year-old woman with no past medical history and taking no conventional medications ingested an herbal preparation marketed for "internal cleansing." Its ingredients were neither known to the patient nor listed on the accompanying literature. The next morning, nausea, vomiting, and weakness developed. In the emergency department, her blood pressure was 110/60 mm Hg, and her pulse rate was 30 beats/min. Her ECG revealed a junctional rhythm at a rate of 30 beats/min and a digitalis effect on the ST segments. After empiric therapy with 10 vials of digoxin-specific Fab (Digibind), her symptoms resolved, and she reverted to a sinus rhythm at a rate of 68 beats/min. Her serum digoxin concentration measured by means of the fluorescence polarization immunoassay (Abbott TDx) was 1.7 ng/mL. Further serum analysis with the Tina Quant digoxin assay, a more digoxin-specific immunoassay, found a concentration of 0.34 ng/mL, and an enzyme immunoassay for digitoxin revealed a concentration of 20 ng/mL (therapeutic range 10 to 30 ng/mL). Serum analysis by means of high-performance liquid chromatography revealed the presence of active digitoxin metabolites; the parent compound was not present. When the diagnosis of cardioactive steroid poisoning is suspected clinically, laboratory analysis can confirm the presence of cardioactive steroids by using immunoassays of varying specificity. An empiric dose of 10 vials of digoxin-specific Fab might be beneficial in patients poisoned with an unknown cardioactive steroid.

Acute plant poisoning and antitoxin antibodies

Plant poisoning is normally a problem of young children who unintentionally ingest small quantities of toxic plants with little resulting morbidity and few deaths. In some regions of the world, however, plant poisonings are important clinical problems causing much morbidity and mortality. While deaths do occur after unintentional poisoning with plants such as Atractylis gummifera (bird-lime or blue thistle) and Blighia sapida (ackee tree), the majority of deaths globally occur following intentional self-poisoning with plants such as Thevetia peruviana (yellow oleander) and Cerbera manghas (pink-eyed cerbera or sea mango). Antitoxins developed against colchicine and cardiac glycosides would be useful for plant poisonings--anti-digoxin Fab fragments have been shown to be highly effective in T. peruviana poisoning. Unfortunately, their great cost limits their use in the developing world where they would make a major difference in patient management. Therapy for some other plant poisonings might also benefit from the development of antitoxins. However, until issues of cost and supply are worked out, plant antitoxins are going to remain a dream in many of the areas where they are now urgently required.

The Fab fragment of anti-digoxin antibody (digibind) binds digitoxin-like immunoreactive components of Chinese medicine Chan Su: monitoring the effect by measuring free digitoxin

Chan Su, a Chinese medicine prepared from the skin glands of Chinese toads, is used in the treatment of cardiovascular diseases. Severe toxicity and even death has been reported from overdose with Chan Su. The cardiotonic effect of Chan Su is attributed to bufadienolides, which also have apparent digitoxin activity. We demonstrated that these components of Chan Su could be neutralized by digibind, both in vitro and in vivo. For in vitro experiments, we supplemented drug-free serum pools with aqueous extract of Chan Su. Then, to aliquots of serum pool containing Chan Su, various amounts of digibind (10, 25 or 50 microg/ml of serum) were added. After incubation, total and free digitoxin concentrations (in the protein-free ultrafiltrate) were measured using the fluorescence polarization immunoassay (FPIA) and a FLX/TDx analyzer. For in vivo experiments, mice were fed with Chan Su by gavage. After 45 min, 200 microg of digibind was administered by injection. Fifteen minutes after injection, blood was collected for analysis of total and free apparent digitoxin activities. We observed complete removal of apparent digitoxin activity from protein-free ultrafiltrate both in vitro and in vivo by digibind, indicating that digibind successfully binds Chan Su. We conclude that digibind neutralizes Chan Su, and measuring the free digitoxin concentrations can monitor such an effect.

Effects of resibufogenin from toad venom on isolated Purkinje fibers

Chan su (dried toad venom) is a traditional Chinese medicine obtained from the skin venom gland of the toad. Chan su has long been used as a therapeutic agent in China and other Asian countries. Recent reports indicate that Chan su toxicity carries a high mortality rate in the United States. This study focused upon the cardiac electrophysiological and electro-toxicity effects of resibufogenin (RBG), one of the major components in Chan su. Action potentials of isolated sheep and canine heart Purkinje fibers were studied using glass microelectrode recording techniques. The results indicate that RBG significantly affected all parameters of transmembrane action potential, induced delayed after depolarization, and triggered arrhythmias in sheep and canine Purkinje fibers.

Herbal and alternative medicine

An extensive range of herbal and dietary supplements is now available, and use of these products by ED patients is fairly common. Emergency physicians should be familiar with some of the products used more frequently for common complaints. Emergency personnel also should be vigilant for toxic syndromes resulting from ingestion of certain of these products and be wary of possible toxicity from any of these supplements owing to their minimal quality control and absence of FDA regulation.

Bufo marinus intoxication in dogs: 94 cases (1997-1998)

OBJECTIVE

To determine history, clinical and electrocardiographic abnormalities, treatment, and outcome of dogs exposed to toxins produced by the Bufo marinus toad.

DESIGN

Retrospective study.

ANIMALS

94 dogs.

PROCEDURE

Medical records of dogs examined between July 1997 and July 1998 for which a diagnosis of toad intoxication had been made on the basis of history and physical examination findings were reviewed.

RESULTS

Most (66) dogs were treated during the spring and summer. For 54 dogs, exposure to toads had been witnessed. For the remaining 40, toad intoxication was diagnosed on the basis of history and clinical signs. The most common clinical signs were neurologic abnormalities, hyperemic mucous membranes, ptyalism, recumbency or collapse, tachypnea, and vomiting. The oral cavity was lavaged with tap water in all dogs. Fifty-two dogs were hospitalized for treatment. Body weight of dogs hospitalized > 2 hours was significantly less than that of dogs treated as outpatients. The most common electrocardiographic findings were sinus arrhythmia, sinus tachycardia, and normal sinus rhythm. Eighty-nine dogs recovered fully, 4 died, and 1 was euthanatized.

CONCLUSIONS AND CLINICAL RELEVANCE

In areas in which B marinus toads are endemic, toad intoxication should be considered in the differential diagnosis for dogs with an acute onset of neurologic abnormalities, hyperemic mucous membranes, and ptyalism, especially during the spring and summer months. The prognosis is good for dogs with toad intoxication that receive appropriate treatment.

Anti-digoxin Fab fragments in cardiotoxicity induced by ingestion of yellow oleander: a randomised controlled trial

BACKGROUND

Severe cardiac glycoside cardiotoxicity after ingestion of yellow oleander seeds is an important problem in rural areas of Sri Lanka. Currently, patients must be transferred to the capital for temporary cardiac pacing. We did a randomised controlled trial to investigate whether anti-digoxin Fab could reverse serious oleander-induced arrhythmias.

METHODS

After a preliminary dose-finding study, 66 patients who presented to hospital with a serious cardiac arrhythmia were randomised to receive either 1200 mg of anti-digoxin Fab or a saline placebo. A 12-lead electrocardiogram, 3 min rhythm strip, and blood sample for measurement of electrolytes and cardiac glycosides were taken before treatment and at 12 timepoints thereafter.

FINDINGS

34 patients received anti-digoxin Fab and 32 received placebo. The presenting arrhythmia had resolved completely after 2 h in 15 antibody-treated patients and two controls (p<0.001); 24 and five patients, respectively, were in sinus rhythm at 8 h (p<0.001). Kaplan-Meier analysis of time to first reversal showed a significant response to anti-digoxin Fab. The heart rate increased in cases, from 49.1 per min at baseline to 66.8 at 2 h, but not in controls (50.6 per min at baseline to 51.5; p<0.001). Mean serum potassium concentrations decreased from 4.9 mmol/L to 4.1 mmol/L at 2 h in cases; no such decrease occurred in controls.

INTERPRETATION

Anti-digoxin Fab fragments are a safe and effective treatment for serious cardiac arrhythmias induced by yellow oleander. Their use in small rural hospitals in Sri Lanka should minimise costly transfer of patients and reduce the numbers of deaths; however, further study will be required to confirm this reduction.

Isolation and Characterization of Human Monoclonal Antibodies to Digoxin

Fab preparations of sheep polyclonal anti-digoxin Abs have proven useful for reversal of the toxic effects of digoxin overdoses in patients. Unfortunately, the use of foreign species proteins in humans is limited because of the potential for immunological responses that include hypersensitivity reactions and acute anaphylaxis. Immunization of recently developed transgenic mice, whose endogenous μ heavy and κ light chain Ig genes are inactivated and which carry human Ig gene segments, with a digoxin-protein conjugate has enabled us to generate and isolate eight hybridoma cell lines secreting human sequence anti-digoxin mAbs. Six of the mAbs have been partially characterized and shown to have high specificity and low nanomolar affinities for digoxin. In addition, detailed competition binding studies performed with three of these mAbs have shown them to have distinct differences in their digoxin binding, and that all three structural moieties of the drug, the primary digitoxose sugar, steroid, and five-member unsaturated lactone ring, contribute to Ab recognition.

Efficacy of digoxin specific Fab fragments (Digibind) in the treatment of toad venom poisoning

Chan Su, a traditional Chinese medication, and Love Stone, a topical aphrodisiac, are both made from dried venom of the toad bufo bufo gargarizans and contain bufalin, cinobufotalin, cinobufagin, and other cardioactive steroids of the bufadienolide class. Deaths have occurred following ingestion of these products and the clinical course resembles digoxin toxicity. The purpose of this study was to determine the efficacy of digoxin specific Fab fragments in treating Chan Su poisoning. An ethanolic extract was prepared from Chan Su. Digoxin specific Fab fragments were reconstituted in normal saline to a concentration of 80 mg/ml. An approximate LD90 dose was determined in preliminary experiments. Mice were then randomly divided into a treatment group of 15 mice and a control group of 30 mice. The treatment group was pretreated with 20 ml/kg of digoxin specific Fab fragment solution by intraperitoneal injection at t = 0, followed by 10 ml/kg of digoxin specific Fab fragments intraperitoneal at t = 30 min. The control group was pretreated with equal volumes of intraperitoneal normal saline at the same times. Immediately following the 30 min injection, both groups were given the estimated LD90 dose of Chan Su extract by subcutaneous injection. An endpoint of survival at 6 h was chosen after preliminary results showed that all deaths occurred in the first 4 h. All 30 of the control mice had seizures followed by death compared to 11 seizures and 7deaths in the 15 treatment mice. These results were statistically significant by Fisher's exact test (p = 0.00003 for mortality and p = 0.009 for seizures). Digoxin specific Fab fragments are effective in the treatment of Chan Su poisoning in mice and may be effective for poisoning by other cardioactive steroids of the bufadienolide class.

Epidemic of self-poisoning with seeds of the yellow oleander tree (Thevetia peruviana) in northern Sri Lanka

Deliberate self-harm is an important problem in the developing world. Ingestion of yellow oleander seeds (Thevetia peruviana) has recently become a popular method of self-harm in northern Sri Lanka -- there are now thousands of cases each year. These seeds contain cardiac glycosides that cause vomiting, dizziness, and cardiac dysrhythmias such as conduction block affecting the sinus and AV nodes. This paper reports a study of the condition's mortality and morbidity conducted in 1995 in Anuradhapura General Hospital, a secondary referral centre serving 750 000 people in Sri Lanka's north central province. 415 cases were admitted to the hospital during 11 months; 61% were women and 46% were less than 21 years old. A prospective study of 79 patients showed that 6% died soon after admission. 43% presented with marked cardiac dysrhythmias which necessitated ther transfer to the coronary care unit in Colombo for prophylactic temporary cardiac pacing. The reasons for the acts of self-harm were often relatively trivial, particularly in children; most denied that they wished to die. Unfortunately, the case fatality rate for oleander poisoning in Sri Lanka is at least 10%. This epidemic is not only causing many unnecessary deaths, it is also putting immense stress on the already stretched Sri Lankan health services. There is an urgent need for an intervention which could be used in rural hospitals, thus preventing the hazardous and expensive emergency transfer of patients to the capital.