Acute digitalis intoxication--is pacing still appropriate?

Diagnosis and practical management of digoxin toxicity: a narrative review and consensus

There are currently no universally accepted guidelines for the management of digoxin toxicity. In the absence of clinical practice guidelines, a set of consensus recommendations for management of digoxin toxicity in the clinical setting were developed through a modified Delphi approach. The recommendations highlight the importance of early recognition of signs of potentially life-threatening toxicity that requires immediate treatment with digoxin-specific antibodies. The consensus identifies a straightforward approach to dosing immune antibody fragments according to the presence or absence of signs of life-threatening toxicity. Supportive measures and management of specific signs of toxicity are also covered.

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.

Foxglove poisoning: diagnostic and therapeutic differences with medicinal digitalis glycosides overdose

We report a case of a 19-year-old woman who ingested Digitalis purpurea leaves as a suicide attempt. She developed gastro-intestinal symptoms, loss of colour vision, cardiac conduction disturbances as well as an elevated serum potassium. Treatment was initiated in analogy to medicinal digoxin poisoning by means of digoxin-specific Fab-fragments with a good effect. However during the further course we faced difficulties of prolonged intestinal absorption and inability to estimate the ingested dose or half-life of the vegetal cardiac glycoside compounds. To prevent further absorption and interrupt enterohepatic recycling, multi-dose activated charcoal was administered. Because of a relapse of cardiac conduction disturbances and hyperkalemia, two supplementary doses of Fab-fragments were given, up to a total dose of nineteen vials (one vial containing 40 mg). The important diagnostic and therapeutic differences of vegetal digitalis intoxication as compared to medicinal intoxication and the applicability of existing guidelines on medicinal digitalis intoxication in the light of these differences will be discussed here.

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.

Pharmacological treatment of cardiac glycoside poisoning

Cardiac glycosides are an important cause of poisoning, reflecting their widespread clinical usage and presence in natural sources. Poisoning can manifest as varying degrees of toxicity. Predominant clinical features include gastrointestinal signs, bradycardia and heart block. Death occurs from ventricular fibrillation or tachycardia. A wide range of treatments have been used, the more common including activated charcoal, atropine, β-adrenoceptor agonists, temporary pacing, anti-digoxin Fab and magnesium, and more novel agents include fructose-1,6-diphosphate (clinical trial in progress) and anticalin. However, even in the case of those treatments that have been in use for decades, there is debate regarding their efficacy, the indications and dosage that optimizes outcomes. This contributes to variability in use across the world. Another factor influencing usage is access. Barriers to access include the requirement for transfer to a specialized centre (for example, to receive temporary pacing) or financial resources (for example, anti-digoxin Fab in resource poor countries). Recent data suggest that existing methods for calculating the dose of anti-digoxin Fab in digoxin poisoning overstate the dose required, and that its efficacy may be minimal in patients with chronic digoxin poisoning. Cheaper and effective medicines are required, in particular for the treatment of yellow oleander poisoning which is problematic in resource poor countries.

Cardiotoxicodynamics: Toxicity of Cardiovascular Xenobiotics

Maintaining adequate tissue perfusion depends on a variety of factors, all of which can be influenced by xenobiotics (substances foreign to the body, including pharmaceuticals, chemicals, and natural compounds). Volume status, systemic vascular resistance, myocardial contractility, and cardiac rhythm all play a significant role in ensuring hemodynamic stability and proper cardiovascular function. Direct effects on the nervous system, the vasculature, or the heart itself as well as indirect metabolic effects may play a significant role in the development of cardiotoxicity. This article is dedicated to discussion of the disruption of cardiovascular physiology by xenobiotics.

Utility of the electrocardiogram in drug overdose and poisoning: theoretical considerations and clinical implications

The ECG is a rapidly available clinical tool that can help clinicians manage poisoned patients. Specific myocardial effects of cardiotoxic drugs have well-described electrocardiographic manifestations. In the practice of clinical toxicology, classic ECG changes may hint at blockade of ion channels, alterations of adrenergic tone, or dysfunctional metabolic activity of the myocardium. This review will offer a structured approach to ECG interpretation in poisoned patients with a focus on clinical implications and ECG-based management recommendations in the initial evaluation of patients with acute cardiotoxicity.

Critical cardiovascular skills and procedures in the emergency department

The management of cardiovascular emergencies is a fundamental component of the practice of an emergency practitioner. Delays in the evaluations and management can lead to significant morbidity or mortality. It is of vital importance to be familiar with procedures such as pericardiocentesis, cardioversion, defibrillation, temporary pacing, and options for the management of tachyarrhythmias. This article discusses the most common cardiovascular procedures encountered in an emergency setting, including the indications, contraindications, equipment, technique, and complications for each procedure.

Diurnal variation in probability of death following self-poisoning in Sri Lanka--evidence for chronotoxicity in humans

BACKGROUND

The absorption, distribution, metabolism and elimination of medicines are partly controlled by transporters and enzymes with diurnal variation in expression. Dose timing may be important for maximizing therapeutic and minimizing adverse effects. However, outcome data for such an effect in humans are sparse, and chronotherapeutics is consequently less practised. We examined a large prospective Sri Lankan cohort of patients with acute poisoning to seek evidence of diurnal variation in the probability of survival.

METHODS

In all, 14 840 patients admitted to hospital after yellow oleander (Cascabela thevetia) seed or pesticide [organophosphorus (OP), carbamate, paraquat, glyphosate] self-poisoning were investigated for variation in survival according to time of ingestion.

RESULTS

We found strong evidence that the outcome of oleander poisoning was associated with time of ingestion (P < 0.001). There was weaker evidence for OP insecticides (P = 0.041) and no evidence of diurnal variation in the outcome for carbamate, glyphosate and paraquat pesticides. Compared with ingestion in the late morning, and with confounding by age, sex, time of and delay to hospital presentation and year of admission controlled, case fatality of oleander poisoning was over 50% lower following evening ingestion (risk ratio = 0.40, 95% confidence interval 0.26-0.62). Variation in dose across the day was not responsible.

CONCLUSIONS

We have shown for the first time that timing of poison ingestion affects survival in humans. This evidence for chronotoxicity suggests chronotherapeutics should be given greater attention in drug development and clinical practice.

Toxic bradycardias in the critically ill poisoned patient

Cardiovascular drugs are a common cause of poisoning, and toxic bradycardias can be refractory to standard ACLS protocols. It is important to consider appropriate antidotes and adjunctive therapies in the care of the poisoned patient in order to maximize outcomes. While rigorous studies are lacking in regards to treatment of toxic bradycardias, there are small studies and case reports to help guide clinicians' choices in caring for the poisoned patient. Antidotes, pressor support, and extracorporeal therapy are some of the treatment options for the care of these patients. It is important to make informed therapeutic decisions with an understanding of the available evidence, and consultation with a toxicologist and/or regional Poison Control Center should be considered early in the course of treatment.

Cutaneous absorption of Oleander: Fact or fiction

Cardiac conduction disorders following oral ingestion of Oleander plant materials were documented earlier. Transcutaneous absorption of yellow oleander (Thevetia peruviana) leaf extract applied over non intact skin (raw wound) resulting in reversible cardiac conduction disorder observed in four healthy males who were free from any other systemic or electrolyte or metabolic disorders or exposure to pesticide or toxins is reported for the first time. Their hematological, biochemical, clinical, and echocardiogram status were within normal limits and free of any abnormalities. One among the four, presented for weakness and breathlessness (class II). He had bradycardia with Mobitz II block and hypotension without any other demonstrable localizing signs. The other three were identified in the community and without any symptoms. However, their ECG revealed bradycardia with Mobitz I block in two and complete heart block in the other. All of the four recovered well without any untoward events. Hence, it is suggested that physicians and practitioners have to elicit history and route of administration of unconventional therapy, whenever they are confronted with clinical challenges and during medical emergencies before embarking final decision.

Clinical features and successful management of suicidal digoxin toxicity without use of digoxin-specific antibody (Fab) fragments – is it possible?

A retrospective study of 147 consecutive cases of suicidal digoxin poisoning was undertaken in order to determine the severity and outcome of toxicity without use of digoxin-specific Fab fragments. This study showed that suicidal digoxin poisoning in young patients is usually mild to moderate; even underlying cardiac disease and chronic use of digoxin has no effect on the severity of toxicity and incidence of lethal dysrhythmia in these cases. This type of toxicity responds appropriately to conventional treatment.

It could have happened to Van Gogh: a case of fatal purple foxglove poisoning and review of the literature

Although death owing to the toxic effects of the therapeutic Digitalis lanata extract, digoxin has been reported, there are no reported cases of fatal Digitalis purpurea (digitoxin) plant intoxication in humans in the literature. We describe a case of ingestion of Digitalis purpurea in a 64-year-old man, which was fatal despite administration of Digibind. A review of the literature and aspects of management of plant digitalis poisoning are discussed.

Antidotes for acute cardenolide (cardiac glycoside) poisoning

BACKGROUND

Cardenolides are naturally occurring plant toxins which act primarily on the heart. While poisoning with the digitalis cardenolides (digoxin and digitoxin) are reported worldwide, cardiotoxicity from other cardenolides such as the yellow oleander are also a major problem, with tens of thousands of cases of poisoning each year in South Asia. Because cardenolides from these plants are structurally similar, acute poisonings are managed using similar treatments. The benefit of these treatments is of interest, particularly in the context of cost since most poisonings occur in developing countries where resources are very limited.

OBJECTIVES

To determine the efficacy of antidotes for the treatment of acute cardenolide poisoning, in particular atropine, isoprenaline (isoproterenol), multiple-dose activated charcoal (MDAC), fructose-1,6-diphosphate, sodium bicarbonate, magnesium, phenytoin and anti-digoxin Fab antitoxin.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, the Controlled Trials Register of the Cochrane Collaboration, Current Awareness in Clinical Toxicology, Info Trac, www.google.com.au, and Science Citation Index of studies identified by the previous searches. We manually searched the bibliographies of identified articles and personally contacted experts in the field.

SELECTION CRITERIA

Randomised controlled trials where antidotes were administered to patients with acute symptomatic cardenolide poisoning were identified.

DATA COLLECTION AND ANALYSIS

We independently extracted data on study design, including the method of randomisation, participant characteristics, type of intervention and outcomes from each study. We independently assessed methodological quality of the included studies. A pooled analysis was not appropriate.

MAIN RESULTS

Two randomised controlled trials were identified, both were conducted in patients with yellow oleander poisoning. One trial investigated the effect of MDAC on mortality, the relative risk (RR) was 0.31 (95% confidence interval (CI) 0.12 to 0.83) indicating a beneficial effect. The second study found a beneficial effect of anti-digoxin Fab antitoxin on the presence of cardiac dysrhythmias at two hours post-administration; the RR was 0.60 (95% CI 0.44 to 0.81). Other benefits were also noted in both studies and serious adverse effects were minimal. Studies assessing the effect of antidotes on other cardenolides were not identified. One ongoing study investigating the activated charcoal for acute yellow oleander self-poisoning was also identified.

AUTHORS' CONCLUSIONS

There is some evidence to suggest that MDAC and anti-digoxin Fab antitoxin may be effective treatments for yellow oleander poisoning. However, the efficacy and indications of these interventions for the treatment of acute digitalis poisoning is uncertain due to the lack of good quality controlled clinical trials. Given pharmacokinetic differences between individual cardenolides, the effect of antidotes administered to patients with yellow oleander poisoning cannot be readily translated to those of other cardenolides. Unfortunately cost limits the use of antidotes such as anti-digoxin Fab antitoxin in developing countries where cardenolide poisonings are frequent. More research is required using relatively cheap antidotes which may also be effective.

Successful treatment of oleander intoxication (cardiac glycosides) with digoxin-specific Fab antibody fragments in a 7-year-old child

A 7-year-old girl presented six hours after ingestion of a yellow oleander seed (Thevetia peruviana) with severe emesis, change in colour vision and complete heart block. Initial treatment with phenytoin and isoprenalin infusion led to intermittent supraventricular and ventricular tachycardia. The patient was then treated with two intravenous doses of 190 mg of digoxin-specific Fab antibody fragments (Digibind). Subsequently the patient's rhythm reverted to sinus rhythm and the symptoms resolved within 2 hours.

CONCLUSION

administration of digoxin-specific Fab antibody fragments in an otherwise healthy child after oleander intoxication is safe and without adverse reactions.

[Nerium oleander self poisoning treated with digoxin-specific antibodies]

A chronically depressed 44-year-old man was rescued by the French medicalised ambulance service four hours after the ingestion of Nerium oleander leaves in a suicide attempt. Cardiotoxicity was evidenced by the presence of bradycardia with mental confusion and vomiting. The patient was empirically treated in the prehospital phase with a single dose of digoxin-specific Fab antibody fragments (Digidot). In spite of this treatment, the patient presented a new episode of important bradycardia (25 b/minute). Thereafter, the patient's rhythm stabilized and neurological signs and vomiting resolved. The patient recovered uneventfully and was discharged from the intensive care unit two days later.

Digoxin-Specific Antibody Fragments

Digitalis glycoside poisoning is an important clinical problem and the development of digoxin-specific antibody fragments (Fab) 30 years ago has changed clinical practice. Nevertheless, doubts still exist as to the appropriate dose indications for therapy. This paper reviews relevant literature, describes the difficulties associated with current treatment protocols and proposes an approach to therapy, which is based on theoretical principles and evidence gleaned from currently available clinical data sets. In patients with 'acute' poisoning, serum digoxin concentrations do not equate to the total body burden, as tissue distribution will not have occurred, and the calculations for present protocols, which use serum concentrations, are therefore likely to result in too much antibody being administered. Since a therapeutic quantity of digoxin will have little effect in a normal individual, complete neutralisation of all digoxin is also unnecessary. The pharmacokinetic and dynamic logic of using a smaller initial loading dose than predicted from total body calculations is rational. It is recommended that half the calculated loading dose, either based on serum concentration or history, should be administered and the impact on clinical features observed. If a clinical response is not seen within 1-2 hours, a further similar dose should be given. In the event of a full response, patients should be monitored for 6-12 hours; a second dose should only be given in the event of recurrence of toxicity. In patients with 'chronic' digoxin poisoning, the serum digoxin concentration will reflect the total body load. However, since such patients are invariably receiving digoxin for therapeutic purposes, full neutralisation is again not indicated. In addition, tissue redistribution of digoxin from deeper stores will occur following the binding of biologically active digoxin in the circulation. This process will occur over a number of hours and if the total calculated dose of antibody is administered in a single bolus, significant quantities will be excreted prior to redistribution of digoxin. Pharmacokinetic logic, therefore, suggests that half the calculated loading dose, based on serum concentration, should be administered and the impact on clinical features observed; a second dose should be given in the event of recurrence of toxicity.

Deaths due to absence of an affordable antitoxin for plant poisoning

There is a severe shortage of affordable antivenoms and antitoxins in the developing world. An anti-digoxin antitoxin for oleander poisoning was introduced in Sri Lanka in July, 2001, but because of its cost, stocks ran out in July, 2002. We looked at the effect of its introduction and withdrawal on case fatality, and determined its cost-effectiveness. The antitoxin strikingly reduced the case fatality; its absence resulted in a three-fold rise in deaths. At the present price of US2650 dollars per course, every life saved cost 10209 dollars and every life year cost 248 dollars. Reduction of the antitoxin's price to 400 dollars would reduce costs to 1137 dollars per life gained; a further reduction to 103 dollars would save money for every life gained. Treatments for poisoning and envenoming should be included in the present campaign to increase availability of affordable treatments in the developing world.

Treatment of hyperkalemia in a patient with unrecognized digitalis toxicity

Cardiac glycoside toxicity is frequently associated with hyperkalemia and dysrhythmias in patients with renal insufficiency. Two common therapeutic options for these complications (calcium and transvenous cardiac pacing) are considered contraindicated in the setting of cardiac glycoside toxicity. We present the case of a patient presenting with a pronounced bradydysrhythmia and hyperkalemia who was treated with intravenous calcium and transvenous cardiac pacing and later found to have digitalis toxicity and acute renal failure. There were no adverse events associated with the therapies. The patient received digoxin-specific Fab fragments and hemodialysis as definitive therapeutic modalities. The case and the relevant literature evaluating the interaction of calcium salts and cardiac pacing in the setting of cardiac glycoside toxicity are discussed.

Toxicologic myocardial sensitization

Drug-induced polymorphic ventricular tachycardia (torsades de pointes) may lead to syncope or sudden cardiac death. One mechanism by which drugs and toxins may predispose to the development of this malignant dysrhythmia is through their ability to produce myocardial sensitization. The concept of myocardial sensitization actually represents a series of events involving altered cellular repolarization produced by blockade of myocardial potassium channels. Altered potassium ion flow raises the likelihood that an ectopic beat will occur via an early afterdepolarization and simultaneously alters the myocardial tissue to make it favorable for reentrant dysrhythmias, such as torsades de pointes, to propagate. Alternatively, calcium overload of the myocyte produces ectopy by causing delayed afterdepolarizations, which if the substrate for reentry is present, will result in ventricular tachycardia. This paper discusses the mechanisms underlying the production of both the altered myocardial substrate and the afterdepolarizations.

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.

[Systematic review of the effectiveness and indications of antidigoxin antibodies in the treatment of digitalis intoxication]

INTRODUCTION AND OBJECTIVES

Cardiac glucoside intoxication is a frequent medical problem given the following: the very narrow therapeutic range, its use in advanced aged patients, in patients with altered renal function, and because of interaction with other drugs. There are two types of digitalis intoxication: one that appears as a complication of the treatment with digitalis, and the other as a result of an accidental ingestion or in suicide attempt. The objective of this study was to review and assess the level of scientific evidence on the effectiveness and the indications of use of Fab fragments of antidigoxine antibodies.

METHODS

A systematic bibliographic search in the following databases was made: MEDLINE, The Cochrane Library, The Iowa Drug Information Service, Embase, LMS/R&D Insight, and Indice Médico Español. The selected papers were classified according to their level of scientific evidence.

RESULTS

Abstracts of 252 references were reviewed. In the reviewed bibliography no controlled, randomized trials were found. Most of the studies found are descriptions of case series or single cases that were treated with antidigoxin Fab fragments. These types of studies provide little or no scientific evidence to speak of. None of the treatment regimes with antidigoxin antibody Fab fragments so far proposed have proven to be valid in a controlled, randomized clinical trial.

CONCLUSIONS

There is a very high level of concordance among the studies reviewed with regards to the efficacy and the indications for the use of Fab fragments in severe acute accidental digitalis intoxication and in suicide attempts. Regarding those intoxications that result in patients undergoing digitalis therapy, usual therapeutic approach is traditional treatment and the monitorization of the severity of the intoxication.

Mechanisms and management of proarrhythmia

It is now well recognized that therapy with antiarrhythmic drugs can not only suppress cardiac arrhythmias, but also may increase their frequency or provoke new ones. Specific proarrhythmia syndromes, each with a distinct underlying mechanism and approach to therapy, have been described. The best-recognized examples are digitalis intoxication, proarrhythmia associated with sodium-channel block, and torsade de pointes occurring during QT-prolonging therapies. In the case of sodium-channel blockers, 2 forms of proarrhythmia are commonly recognized: slow atrial flutter with 1:1 atrioventricular conduction, and frequent ventricular tachycardia ([VT], most often found in patients with pre-existing VT reentrant circuits). In all cases, the best approach to therapy is to identify patients at risk (and thereby avoid therapy entirely), to recognize proarrhythmia when it occurs, to withdraw offending agent(s), and to use specific corrective therapies when available. Although most recognized episodes of proarrhythmia are thought to occur early in drug therapy, the increased mortality during chronic antiarrhythmic therapy demonstrated in large randomized trials suggests this phenomenon can also develop during long-term drug treatment. The recognition of proarrhythmia and the delineation of its underlying mechanisms should not only improve therapy with available drugs, but may also direct development of newer agents devoid of this potential.

Percutaneous cardiopulmonary bypass for therapy resistant cardiac arrest from digoxin overdose

A 79-year 65 kg male called the ambulance service 4 h after ingestion of 100 tablets of digoxin 0.1 mg complaining of nausea and vomiting. The ECG showed an idioventricular escape rhythm with a heart rate of 30/min. After 0.5 mg atropine, heart rate increased to 80/min. Soon after admission to the emergency department, the patient developed electromechanical dissociation. Due to persistent cardiac arrest, percutaneous cardiopulmonary bypass was started, and the ECG rhythm changed to ventricular fibrillation. Several attempts to terminate ventricular fibrillation by electrical defibrillation failed. Fifty-eight minutes after cardiac arrest, antidigoxin-Fab was administered and 1 h 25 min after cardiac arrest, ventricular fibrillation was terminated by the tenth electrical defibrillation attempt. Initially, the patient's overall status improved over the next 2 days, but then he developed a severe adult respiratory distress syndrome and died of unresponsive septic shock 12 days after ingestion of digoxin. This case demonstrates that percutaneous cardiopulmonary bypass may provide support in patients with cardiac arrest due to massive digoxin overdose. This temporary support can maintain adequate tissue perfusion during the time required for drug neutralization in order to achieve successful defibrillation. Percutaneous cardiopulmonary bypass should be considered in patients with severe, but temporary cardiac dysfunction due to a life-threatening drug overdose.

Poisoning and drug overdose

Poisoning is a common cause for intensive care unit admission for both children and adults, and most poisoning victims are effectively treated using standard decontamination measures and supportive care. For a small number of poisons, acceleration of toxin removal with hemodialysis or hemofiltration is indicated. Similarly, specific antidotes are indicated in a few selected circumstances. Rarely, patients may benefit from more aggressive supportive techniques such as cardiopulmonary bypass.

Modifying toxicokinetics with antidotes

Five approaches may be described through which antidotes can modify toxicokinetics: (1) Decreased bioavailability of the toxins; (2) Cellular redistribution of the toxin in the organism; (3) Promotion of elimination in an unchanged form; (4) Slowing of metabolic activation pathways; (5) Acceleration of metabolic deactivation pathways. However, the ability to modify toxicokinetics with a new treatment, while demonstrating an understanding of the mechanism of action, must never be construed to be, in and of itself, the goal of therapy. The ultimate evaluation of an antidote modifying toxicokinetics is strictly clinical.