Acetaminophen overdose: a 48-hour intravenous N-acetylcysteine treatment protocol

Nitrogen and oxygen molecules in meningitis-associated labyrinthitis and hearing impairment

Pneumococcal meningitis remains a serious disease with a case fatality rate of 15%-25%. Furthermore, long-term residues affect up to 50% of survivors. One of the most frequent sequelae is sensorineural hearing loss, which occurs in 26% of survivors of pneumococcal meningitis. Unfortunately, sufficient treatment regimens are still missing. New insights into the pathology and pathophysiology of meningitis-associated hearing loss have come from animal models of bacterial meningitis. Most likely, bacteria reach the cochlea through the cochlear aquaeduct. Once arrived in the perilymphatic spaces, they induce a severe suppurative labyrinthitis. The blood-labyrinth barrier breaks, hair cells are damaged, and neurons in the spiral ganglion undergo cell death, leading to meningitis-associated hearing loss. Reactive oxygen and nitrogen species, in particular peroxynitrite, seem to be among the crucial mediators of cochlear damage and hearing loss during meningitis. In our rat model of pneumococcal meningitis, adjunctive therapy with the antioxidants and peroxynitrite scavengers Mn(III)tetrakis(4-bencoic acid)-porphyrin (MnTBAP) and N-Acetyl-L-Cystein (NAC) significantly attenuated acute and long-term hearing loss. In several other animal studies of pneumococcal meningitis, adjunctive antioxidant therapy also protected infected animals from intracranial complications. Therefore, the use of antioxidants seems to be a promising future treatment option in pneumococcal meningitis.

Does age matter? Comparing case fatality rates for selected poisonings reported to U.S. poison centers

BACKGROUND

As the elderly population continues to grow, the number of geriatric patients reported to poison centers continues to increase. We believe that older poisoned patients are at an increased risk of death compared to younger adult patients. The objective of this study was to compare the risk of death from selected poisoning between younger (<59) and older (>59) adults.

METHODS

We included adult cases reported to U.S. poison centers between 1995 and 2002. To limit potential confounders, our analysis included single substance ingestions of theophylline, digoxin, benzodiazepines, tricyclic antidepressants, calcium channel antagonists, acetaminophen, and salicylate. We determined the case fatality rate for each poisoning for younger and older adults. We calculated crude odds ratios for each poison and then used logistic regression to adjust for covariates.

RESULTS

Overall we found an increase in the relative rate of death for each poison (range 1.2 to 7.1). After adjustment, each 10-year increase in age was associated with a 36% increase in the odds ratio for death as an outcome. Our findings were limited by the use of poison center data, which does not include data on covariates that may be potential confounders.

Clinical policy: critical issues in the management of patients presenting to the emergency department with acetaminophen overdose

This clinical policy focuses on critical issues concerning the management of patients presenting to the emergency department (ED) with acetaminophen overdose. The subcommittee reviewed the medical literature relevant to the questions posed. The critical questions are: 1. What are the indications for N-acetylcysteine (NAC) in the acetaminophen overdose patient with a known time of acute ingestion who can be risk stratified by the Rumack-Matthew nomogram? 2. What are the indications for NAC in the acetaminophen overdose patient who cannot be risk stratified by the Rumack-Matthew nomogram? Recommendations are provided on the basis of the strength of evidence of the literature. Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies that are based on preliminary, inconclusive, or conflicting evidence, or based on committee consensus. This guideline is intended for physicians working in EDs.

Acetaminophen safety and hepatotoxicity--where do we go from here?

Acetaminophen has been widely used for > 50 years in the treatment of pain and fever and provides for the safe and effective relief of these symptoms. In a small minority of patients, however, acetaminophen is responsible for life-threatening liver injury and accounts for up to 50% of all adult cases of acute liver failure in the US. Although approximately two-thirds of adult overdoses are associated with suicide attempts, many are inadvertent, often due to the use of multiple acetaminophen formulations over many days. Additionally, some individuals appear to experience acetaminophen toxicity at 'therapeutic' doses of < 4 g/day, for reasons unknown. In pediatric populations, the overwhelming majority of acetaminophen overdoses are due to unintentional overdoses, except for the predominance of suicidal ingestions in the teenage population. This article seeks to review the mechanism and metabolism of acetaminophen and the features of toxicity in adults, pediatric and special populations. Additionally, expert opinion is presented herein to aid in reducing the frequency and severity of liver injury from acetaminophen.

A Prospective Evaluation of Shortened Course Oral N-Acetylcysteine for the Treatment of Acute Acetaminophen Poisoning

STUDY OBJECTIVE

Treatment with a shortened duration of oral N-acetylcysteine (20 to 48 hours) after acute acetaminophen poisoning is effective in the prevention of subsequent hepatic failure and death when administered to individuals meeting appropriate laboratory criteria.

METHODS

Individuals with a potentially toxic acetaminophen ingestion according to serum acetaminophen levels were identified prospectively using a large statewide poison control system database throughout a 12-month period. N-acetylcysteine was administered for a minimum of 6 doses (20 hours), after which laboratory studies were obtained. Discontinuation of N-acetylcysteine was recommended by the poison center when 2 criteria were met: serum acetaminophen was undetectable (<10 microg/mL) and liver test results were normal (serum aminotransferase, international normalized ratio). A follow-up questionnaire was administered to individuals treated with N-acetylcysteine for 48 hours or less to ascertain the presence of symptoms consistent with progressive hepatotoxicity.

RESULTS

Of 205 acutely poisoned individuals treated with N-acetylcysteine for 48 hours or less, 195 were successfully contacted after discharge, and 187 of 195 (95.9%) reported no symptoms consistent with hepatic failure. Eight individuals (4.1%) reported abdominal pain or vomiting; however, none received further N-acetylcysteine treatment or additional hospitalization.

CONCLUSION

A shortened duration of treatment with N-acetylcysteine (20 to 48 hours) may be an effective treatment option in individuals considered to be at no further risk of developing liver toxicity according to the fulfillment of appropriate laboratory criteria before N-acetylcysteine discontinuation.

Acetaminophen hepatotoxicity

Acetaminophen is a commonly used antipyretic and analgesic agent. It is safe when taken at therapeutic doses; however, overdose can lead to serious and even fatal hepatotoxicity. The initial metabolic and biochemical events leading to toxicity have been well described, but the precise mechanism of cell injury and death is unknown. Prompt recognition of overdose, aggressive management, and administration of N-acetylcysteine can minimize hepatotoxicity and prevent liver failure and death. Liver transplantation can be lifesaving for those who develop acute liver failure.

[N-acetyl-L-cysteine as a therapeutic option in bacterial meningitis]

Despite antibiotic therapy, supportive intensive care, and adjunctive treatment with dexamethasone, the mortality and morbidity remain high in patients with bacterial meningitis. The intracranial complications that mainly contribute to the poor outcome are in part a result of the production of reactive oxygen and nitrogen species. Experimental studies have shown that the prognosis for bacterial meningitis can be improved by the administration of antioxidants. Especially adjunctive therapy with N-acetyl-L-cystein (NAC) was shown to have mainly positive effects. Since NAC is already in clinical use in high doses for treating other diseases (e.g., acetaminophen intoxication) and only minor side effects have been observed, there is justified hope that adjunctive therapy with NAC could improve the prognosis of patients with bacterial meningitis.

Comparison of oral and i.v. acetylcysteine in the treatment of acetaminophen poisoning

PURPOSE

The efficacy, safety, and cost issues that should be considered when deciding on the appropriate route of acetylcysteine for the treatment of patients with acetaminophen poisoning are reviewed.

SUMMARY

Oral and i.v. acetylcysteine appear to be equally effective when given within 8-10 hours of acetaminophen overdose. Anaphylactoid reactions to i.v. acetylcysteine have generally been reported in 3-6% of acetaminophen-poisoned patients. Dosing errors and hyponatremia have occurred in pediatric patients receiving i.v. acetylcysteine. Several investigators found an increased rate of anaphylactoid reactions in patients treated with i.v. acetylcysteine whose pretreatment serum acetaminophen levels were nontoxic. Compounding i.v. acetylcysteine from the oral preparation is less expensive than using premade i.v. solution. State pharmacy laws dictate whether extemporaneous compounding of acetylcysteine from the oral formulation is allowed. Oral acetylcysteine administration has resulted in minimal anaphylactoid reactions and is safer than i.v. acetylcysteine. Oral therapy should preferentially be considered in patients with asthma or atopic histories. The most important factors to consider when selecting the route of acetylcysteine administration include individual susceptibility, the severity of acetaminophen toxicity, and the time interval between acetaminophen ingestion and initiation of acetylcysteine therapy.

CONCLUSION

Oral acetylcysteine administered within 8-10 hours of acetaminophen overdose prevents liver toxicity in the majority of patients who tolerate it and have no contraindications to therapy. I.V. acetylcysteine should be administered when patients are treated more than 10 hours postingestion of acetaminophen overdose or have underlying conditions preventing oral treatment. Anaphylactoid reactions are rare and occur more frequently in patients treated with the i.v. preparation.

N-Acetylcysteine Partially Reverses Oxidative Stress and Apoptosis Exacerbated by Mg-Deficiency Culturing Conditions in Primary Cultures of Rat and Human Hepatocytes

OBJECTIVE

The effects of magnesium (Mg) deficiency on the rate of oxidative stress and apoptosis in primary cultures of human hepatocytes were compared to cultured rat hepatocytes. The possible reversion by N-acetylcysteine (NAC) in Mg-deficient culturing conditions was evaluated.

METHODS

Incubations were conducted for up to 72 h in media containing a deficient (0-0.4 mM) or a physiological (0.8 mM) Mg concentration, and in the presence or absence of NAC after 24 h of culture in these Mg concentration conditions.

RESULTS

We obtained similar profiles in terms of apoptosis and oxidative stress in primary cultures of human hepatocytes, as compared to rat hepatocytes, i.e. a Mg concentration-dependent effect on the caspase-3 activity and GSH levels after 72 h of culture, caspase-3 activity being highest and GSH levels being lowest in Mg-free cultures. The addition of NAC to culture media after the first 24 h of culture increased GSH concentrations. This was accompanied in Mg-deficient cultures by a decrease in both the caspase-3 activity and the lipid peroxidation. However, when culturing hepatocytes with physiological Mg concentrations, an increase in both caspase-3 activity and lipid peroxidation was observed.

CONCLUSIONS

Our results indicate that Mg deficiency exacerbates the rate of apoptosis in cultured hepatocytes, associated with an increase in oxidative stress, the sensitivity of human hepatocytes being equivalent to that of rat hepatocytes. They also indicate a dual role of NAC and/or GSH, i.e. protective for hepatocytes placed in a Mg-deficient environment, while deleterious for hepatocytes placed in a Mg-physiological environment.

Efficacy of activated charcoal administered more than four hours after acetaminophen overdose

To evaluate whether administration of activated charcoal, in addition to standard N-acetylcysteine (NAC) therapy, after acetaminophen overdose provides additional patient benefit over NAC therapy alone, a 1-year non-randomized prospective, multi-center, observational case series was performed at three poison centers and one poison center system. Entrance criteria were all acute acetaminophen overdoses with: 1) an acetaminophen blood concentration determined to be in the toxic range by the Rumack-Matthew nomogram; and 2) all therapies, including NAC and activated charcoal, initiated between 4 and 16 h post-ingestion. There were 145 patients meeting entrance criteria, of whom 58 patients (40%) received NAC only and 87 patients (60%) received NAC and activated charcoal. Overall, 23 patients had elevations of AST or ALT greater than 1000 IU/L, of which 21 patients received NAC only (38% of total NAC only group) and 2 patients received NAC and activated charcoal (2% of total NAC+AC group). Administration of activated charcoal in this series of patients with toxic acetaminophen concentrations treated with NAC was associated with reduced incidence of liver injury, as measured by elevated serum transaminases and prothrombin times.

New and novel antidotes in pediatrics

Antidotal therapy can be lifesaving in the management of poisoned children. Although supportive care is sufficient in many cases, a specific antidote can significantly reduce morbidity and mortality in a number of poisoning scenarios, and so the pediatric emergency medicine practitioner must be familiar with its indications for use, dosage and administration, and contraindications. A number of new antidotes have emerged in recent years. This review discusses the pediatric uses and limitations of intravenous N-acetylcysteine, octreotide, crotaline Fab antivenom, fomepizole, atropine and pralidoxime autoinjectors and provides some brief discussion on newer antidotes for which data is only starting to emerge.

Interventions for paracetamol (acetaminophen) overdose

BACKGROUND

Poisoning with paracetamol (acetaminophen) is a common cause of hepatotoxicity in the Western World. Inhibition of absorption, removal from the vascular system, antidotes, and liver transplantation are interventions for paracetamol poisoning.

OBJECTIVES

To assess the benefits and harms of interventions for paracetamol overdose.

SEARCH STRATEGY

We identified trials through electronic databases, manual searches of bibliographies and journals, authors of trials, and pharmaceutical companies until December 2005.

SELECTION CRITERIA

Randomised clinical trials and observational studies were included.

DATA COLLECTION AND ANALYSIS

The primary outcome measure was all-cause mortality plus liver transplantation. Secondary outcome measures were clinical symptoms, (eg, hepatic encephalopathy, fulminant hepatic failure), hepatotoxicity, adverse events, and plasma paracetamol concentration. We used Peto odds ratios and odds ratios with 95% confidence intervals (CI) for analysis of outcomes. Random- and fixed-effects meta-analyses were performed.

MAIN RESULTS

Ten small and low-methodological quality randomised trials, one quasi-randomised study, and 48 observational studies were identified. It was not possible to perform relevant meta-analyses of randomised trials that have addressed our outcome measures. Activated charcoal, gastric lavage, and ipecacuanha are able to reduce the absorption of paracetamol, but the clinical benefit is unclear. Of these, activated charcoal seems to have the best risk-benefit ratio. N-acetylcysteine seems preferable to placebo/supportive treatment, dimercaprol, and cysteamine, but N-acetylcysteine's superiority to methionine is unproven. It is not clear which N-acetylcysteine treatment protocol offers the best efficacy. No strong evidence supports other interventions for paracetamol overdose. N-acetylcysteine may reduce mortality in patients with fulminant hepatic failure (Peto OR 0.26, 95% CI 0.09 to 0.94, one trial). Liver transplantation has the potential to be life saving in fulminant hepatic failure, but refinement of selection criteria for transplantation and long-term outcome reporting are required.

AUTHORS' CONCLUSIONS

Our results highlight a paucity of randomised trials on interventions for paracetamol overdose. Activated charcoal seems the best choice to reduce absorption. N-acetylcysteine should be given to patients with overdose but the selection criteria are not clear. No N-acetylcysteine regime has been shown to be more effective than any other. It is a delicate balance when to proceed to liver transplantation, which may be life-saving for patients with poor prognosis.

Acetaminophen Poisoning

Acetaminophen (acetyl-para-amino-phenol or APAP), an antipyretic and analgesic, is a common component in hundreds of over-the-counter and prescription medications. The wide usage of this drug results in many potentially toxic exposures. It is therefore critical for the clinician to be comfortable with the diagnosis and treatment of APAP toxicity. Prompt recognition of APAP overdose and institution of appropriate therapy are essential to preventing morbidity and mortality.

The molecular toxicology of acetaminophen

The history of the development of the analgestic drug acetaminophen is reviewed with an emphasis on the characteristics of its overdose toxicity. The P450-catalyzed oxidation of acetaminophen generates a reactive electrophile that binds covalently to proteins. Involvement of specific P450 enzymes in acetaminophen toxicity can be probed by experiments with knock-out mice. The identification of specific target proteins may help to clarify the mechanism of acetaminophen hepatoxocity.

Acetaminophen overdose in pregnancy

Acetaminophen (APAP) is the most common drug overdose in pregnancy. Available data regarding APAP overdose in pregnancy is limited to case reports and a small prospective case series. APAP has been demonstrated to cross the placenta and in toxic doses may harm the fetal and maternal hepatocytes. Fetal hepatocytes metabolize APAP into both active and toxic metabolites. These toxic metabolites may cause fetal hepatic necrosis. N-acetylcysteine (NAC) has also been demonstrated to cross the placenta and may bind toxic metabolites in both the mother and the fetus. Limited data suggest that the majority of morbidity and mortality from APAP overdose can be averted by initiation of NAC within the first 16 hours of ingestion and possibly even later. NAC may be safely administered during pregnancy and should be initiated early after APAP overdosage. The literature was reviewed through the use of OvidMEDLINE database, encompassing 1966 to the present. Searches were conducted using the key words acetaminophen, paracetamol, N-acetylcysteine, overdose, and hepatotoxicity. The search was further refined by selecting articles that contained these search words together with the key word pregnancy. Only English language papers were reviewed. Articles were selected on the basis of relevance to the topic. Pertinent citations found in the selected articles were also reviewed.

Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually fatal pulmonary disease for which there are no proven drug therapies. Anti-inflammatory and immunosuppressive agents have been largely ineffective. The precise relationship of IPF to other idiopathic interstitial pneumonias (IIPs) is not known, despite the observation that different histopathologic patterns of IIP may coexist in the same patient. We propose that these different histopathologic 'reaction' patterns may be determined by complex interactions between host and environmental factors that alter the local alveolar milieu. Recent paradigms in IPF pathogenesis have focused on dysregulated epithelial-mesenchymal interactions, an imbalance in T(H)1/T(H)2 cytokine profile and potential roles for aberrant angiogenesis. In this review, we discuss these evolving concepts in disease pathogenesis and emerging therapies designed to target pro-fibrogenic pathways in IPF.

Updates on acetaminophen toxicity

APAP is likely to remain a common toxic exposure and continue to cause significant morbidity and mortality. To minimize the harm to patients, it is necessary for the clinician to be aware of the current diagnostic and therapeutic management of APAP poisoning. Despite the bulk of literature on APAP, management strategies are likely to continue to change as more studies are conducted to improve our understanding of nonacute ingestions and the role of prognostic markers in defining those most at risk for life-threatening hepatotoxicity.

A Risk Quantification Instrument for Acute Acetaminophen Overdose Patients Treated With N-Acetylcysteine

STUDY OBJECTIVE

The risk of hepatotoxicity after acute acetaminophen overdose varies with timed serum acetaminophen concentration and delay to treatment. The ability to accurately predict hepatotoxicity is needed to reduce confusion about the optimal treatment regimen for individual patients and the effects of risk modifiers such as ethanol. We quantitatively estimate the risk of hepatotoxicity based on the degree and duration of pretreatment exposure to supratherapeutic concentrations of acetaminophen.

METHODS

We examined all hospitalizations for acute acetaminophen overdose within a retrospective multicenter Canadian registry. We used a previously developed composite measure incorporating timed serum acetaminophen concentration and time to N-acetylcysteine treatment into a single parameter. We then modeled hepatotoxicity on this parameter, as well as age, sex, and ethanol use. Hepatotoxicity was defined as peak aminotransferase level of 1,000 IU/L or greater at 24 hours or longer.

RESULTS

Of 1,270 admitted patients treated mostly with intravenous N-acetylcysteine for less than 24 hours, our model accurately identified the 94 patients who developed hepatotoxicity (discriminatory index 0.93). Hepatotoxicity occurred in none of the 313 patients (95% confidence interval [CI] 0% to 1.0%) above the traditional 150 mug/mL treatment line who were classified as low risk (<1%) using our instrument. After adjustment for severity of exposure, the risk of hepatotoxicity was considerably higher in the absence of coingested ethanol (median hepatotoxic dose 16.5 mmol/L x hour [95% CI 8.74 to 31.0 mmol/L x hour] versus 27.1 mmol/L x hour [95% CI 11.1 to 66.3 mmol/L x hour]), particularly among alcoholics (4.79 mmol/L x hour [95% CI 2.13 to 10.8 mmol/L x hour]).

CONCLUSION

Our risk prediction instrument identifies a large group of low-risk patients for whom 20-hour intravenous N-acetylcysteine therapy is sufficient. Our results suggest that acute and chronic ethanol use dramatically influences acetaminophen toxicity. This work may facilitate the evaluation of individualized treatment strategies for higher-risk patients.

The Australasian Clinical Toxicology Investigators Collaboration randomized trial of different loading infusion rates of N-acetylcysteine

STUDY OBJECTIVE

We determine whether the incidence of adverse events caused by intravenous N -acetylcysteine is significantly less when the initial dose is infused over a 60-minute period compared with the standard infusion period of 15 minutes. A secondary objective is to assess the efficacy of the 2 treatment arms.

METHODS

This was a multicenter, randomized, prospective trial of patients who presented with acetaminophen poisoning and who were treated with N -acetylcysteine and had no history of hypersensitivity to N-acetylcysteine. Patients were randomly assigned to receive the initial dose of N-acetylcysteine over a 15-minute or 60-minute period. Baseline signs and symptoms and adverse events were serially evaluated before and during administration of N -acetylcysteine. Tests of liver injury and coagulation were collected at baseline and then at 12-hour intervals.

RESULTS

The study was designed with an 80% power to detect a halving of the incidence of adverse events. Of 180 evaluable patients, 109 patients were randomized to the 15-minute group and 71 patients were randomized to the 60-minute group. The incidence of drug-related adverse events was 45% in the 15-minute group and 38% in the 60-minute group (95% confidence interval -8% to 22%). The study did not demonstrate a reduction of drug-related adverse outcomes with the 60-minute infusion. Incidence of maximum alanine aminotransferase levels indicating hepatotoxicity (serum level >1,000 IU/L) was 6.8% (5.6% for 15-minute, 8.7% for 60-minute). The difference did not attain statistical significance.

CONCLUSION

This study did not demonstrate a reduction of drug-related adverse outcomes with the 60-minute infusion. The study also confirmed that early treatment with N -acetylcysteine (within 8 hours of ingestion) is more effective than later treatment.

An update of N-acetylcysteine treatment for acute acetaminophen toxicity in children

PURPOSE OF REVIEW

Acetaminophen poisoning accounts for a disproportionate percentage of all toxic ingestions, and can be life-threatening. This article reviews the mechanism and presentation of acetaminophen toxicity, as well as its treatment, including current thinking and treatment recommendations.

RECENT FINDINGS

N-acetylcysteine acts to detoxify acetaminophen in several ways, but primarily by increasing the synthesis and availability of glutathione, which binds and inactivates the highly reactive and hepatotoxic acetaminophen metabolite N-acetyl-p-benzoquinoneimine. The US Food and Drug Administration has approved an intravenous formulation of N-acetylcysteine, thus allowing the treatment time to be decreased from the 72 hr most commonly used for the oral regimen, to only 20 hr. This comes after many years of accepted intravenous N-acetylcysteine use in Europe and Canada, and much controversy as to the superiority of both treatments. This review summarizes this controversy, and offers a framework to develop a safe treatment plan that has the optimal outcome for the patient, as well as reflecting knowledge of the potential caveats at work. It describes side effects of N-acetylcysteine treatment, as well as relative indications to choose one route of treatment over the other.

SUMMARY

Acetaminophen can lead to irreversible liver damage and even death in acute overdose. Outcome is related to the swiftness in which the antidote (N-acetylcysteine) is provided. In the United States, there are now available both the oral and intravenous forms of N-acetylcysteine, and pros and cons exist for each. With brisk and adequate treatment using either route, recovery can be complete, and liver function can be restored.

A patient-tailored N-acetylcysteine protocol for acute acetaminophen intoxication

BACKGROUND

Hepatotoxicity as a result of acetaminophen(APAP) intoxication has become an important problem, but early intervention with N-acetylcysteine (NAC) is effective in preventing hepatic injury. Two NAC regimens are currently approved for acute APAP intoxication: NAC administered orally every 4 hours for 72 hours, and NAC administered intravenously for 20 hours within 8 to 10 hours after ingestion of a potentially hepatotoxic amount of APAP. However, clinical observations suggest that a variable treatment duration may be more appropriate than use of these predetermined, fixed-duration protocols.

OBJECTIVES

This study investigated the tolerability and efficacy of a patient-tailored NAC protocol for acute APAP intoxication by comparing the incidence of hepatotoxicity in patients receiving this protocol and in historical controls receiving 1 of 2 fixed-duration protocols: oral NAC for 72 hours and intravenous NAC for 20 hours within 8 to 10 hours after ingestion of a potentially hepatotoxic amount of APAP.

METHODS

This was a retrospective case series study that included all patients admitted through the emergency department (ED) of the National Taiwan University Hospital with a diagnosis of APAP intoxication between October 1997 and October 2002. According to the patient-tailored protocol, which had been used in the ED since 1997, patients with a serum APAP concentration above the limit for possible risk based on a modified Rumack-Matthew nomogram received oral treatment with NAC 140 mg/kg, followed by maintenance doses of 70 mg/kg every 4 hours. NAC treatment was discontinued when the APAP concentration was <10 mg/L and serum aspartate aminotransferase (AST) was <40 IU/L. For the purposes of assessing clinical outcomes, patients were divided into 3 groups based on duration of treatment: the short-course group (</=36 hours), the intermediate-course group (37-72 hours), and the long-course group (>/=73 hours). The primary outcome measure was development of hepatotoxicity, defined as a serum AST or alanine aminotransferase concentration >1000 IU/L.

RESULTS

Twenty-seven patients were included in the study, 17 in the short-course group, 4 in the intermediate-course group, and 6 in the long-course group. The mean (SD) durations of NAC treatment in the respective groups were 22.1 (5.5) hours, 45.0 (8.2) hours, and 97.3 (33.2) hours. All 6 patients (22%) in the long-course group had hepatotoxicity (peak AST range, 1083-9770 IU/L); their treatment duration ranged from 80 to 164 hours. No patients in the short- or intermediate-course group had evidence of hepatotoxicity. One woman in the long-course group in whom initiation of NAC treatment was delayed by 28 hours died of fulminant hepatic failure. The overall incidence of hepatotoxicity was similar to that in the historical controls.

CONCLUSIONS

In this retrospective case series inpatients who received patient-tailored NAC therapy for acute APAP intoxication, the incidence of hepatotoxicity was low and comparable to that in historical controls who received treatment with 1 of 2 fixed-duration regimens. Use of this protocol may have the potential to shorten hospital stays without increasing the risk to patients. However, the sample size was small, and the findings require confirmation in prospective clinical trials.

A Clinical and Pharmacoeconomic Justification for Intravenous Acetylcysteine

Paracetamol (acetaminophen) poisoning remains the most common exposure reported to US poison information centres and the leading cause of poisoning-related fatalities, despite the availability of an effective antidote, acetylcysteine. Oral acetylcysteine solution has been approved for the management of acetaminophen poisoning in the US for four decades. Until the recent approval of intravenous acetylcysteine in the US, it was necessary to compound the oral solution for intravenous administration. The effectiveness and tolerability of oral and intravenous acetylcysteine for the prevention of hepatotoxicity induced by paracetamol poisoning are well established in the literature. Intravenous acetylcysteine may be preferred over oral administration based on improved tolerability, ease of administration and the shortened course of therapy (20 hours intravenous vs 72 hours oral). The two intravenous acetylcysteine regimens documented in the literature, 48 hours and 20 hours, have similar efficacy when started within 8-10 hours of ingestion. Although there are no legal concerns with continuing the routine compounding of the oral solution to an intravenous product, new standards for pharmacy compounding of sterile preparations set forth by the US Pharmacopoeia highlight that the risk of compounding products for intravenous use must be assessed carefully. Changing the route of administration of a sterile oral solution to an intravenous preparation, when a commercial sterile and pyrogen-free product is available, may not be advisable. The best cost-containment strategies must be used for introduction of the more costly sterile, pyrogen-free intravenous acetylcysteine formulation by hospitals and healthcare systems. The intravenous acetylcysteine product is more cost effective when given for 20 hours than other treatment protocols based on the costs of acetylcysteine and hospitalisation. If used per protocol, the 20-hour intravenous acetylcysteine regimen may decrease hospital length of stay, thereby, offsetting the increased drug cost. Data conflict on the efficacy and administration of intravenous acetylcysteine for off-label uses, such as radiographic contrast media-induced nephropathy prevention and reperfusion in orthotopic liver transplantation. The costs for the intravenous formulation for these indications is significantly higher than use of the oral formulation for oral administration in radiographic contrast media-induced nephropathy prevention and compounded for intravenous use in orthotopic liver transplantation. The oral solution should be retained by healthcare systems for oral and inhalation applications, such as respiratory conditions, oral administration for radiographic contrast media nephropathy prevention, or the use of the 72-hour oral protocol to treat paracetamol poisoning, when the intravenous preparation cannot be used.

What is the rate of adverse events after oral N-acetylcysteine administered by the intravenous route to patients with suspected acetaminophen poisoning?

STUDY OBJECTIVE

We conduct a study to determine the rate of adverse events (anaphylactoid and cardiorespiratory) associated with the use of oral N-acetylcysteine by the intravenous route for the treatment of suspected acetaminophen poisoning and to examine specific variables that may be associated with adverse events.

METHODS

We conducted a retrospective medical record review with explicit criteria. All patients who received oral N-acetylcysteine by the intravenous route from September 1995 to September 2001 were included. Patients were identified by cross-matching 3 databases. Adverse events were divided into categories of cutaneous, systemic, or life threatening. Five reviewers abstracted charts by using a standardized data collection form. Interrater reliability was calculated by using 24 medical records abstracted by all 5 reviewers.

RESULTS

There were 7 adverse events identified in 187 patients (3.7%; 95% confidence interval 1.0% to 6.5%). Six adverse events were cutaneous and responded rapidly to antihistamines. One adverse event was life threatening but not clearly related to N-acetylcysteine. A high rate of antihistamine exposure (53%) was identified before the administration of N-acetylcysteine. Interrater agreement was higher than 95%.

CONCLUSION

Intravenous administration of an oral solution of N-acetylcysteine is associated with a low rate of adverse events and should be considered for selected patients with suspected acetaminophen poisoning.

Toxicology in the critically ill patient

Intoxications present in many forms including: known drug overdose or toxic exposure, illicit drug use, suicide attempt, accidental exposure, and chemical or biological terrorism. A high index of suspicion and familiarity with toxidromes can lead to early diagnosis and intervention in critically ill, poisoned patients. Despite a paucity of evidence-based information on the management of intoxicated patients, a rational and systematic approach can be life saving.

Paracetamol poisoning: Which nomogram should we use?

OBJECTIVES

To determine the type of paracetamol nomograms used in Australasian EDs. To review the literature to determine the evidence base for existing nomograms.

METHODS

A cross sectional descriptive study via postal survey of all Australasian EDs accredited for specialist emergency medicine training by the Australasian College for Emergency Medicine (ACEM). A literature review using Knowledge Finder search engine was employed.

RESULTS

The response rate was 87%. The most commonly used nomogram had a four-hour treatment level of 1300 mumol/L (69%). A total of 22% of respondents used a four-hour treatment level of 1000 mumol/L. Two departments (3%) treated all patients above the 660 mumol/L line. Eleven departments (15%) did not have a treatment line below 1300 mumol/L.

CONCLUSION

Practice varies in Australasian EDs. Patients with paracetamol levels below the 1300 mumol/L have been reported in the literature to develop hepatotoxicity, and deaths have been documented. N-acetylcysteine is extremely safe when used in the recommended dosages.

Acetaminophen intoxication and length of treatment: how long is long enough?

The currently recommended dosing scheme for treating acetaminophen overdose in the United States consists of a loading dose of oral N-acetylcysteine 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses, for a total of 72 hours of oral N-acetylcysteine therapy. This protocol has been both effective and safe. We critically evaluated the evidence that supports reducing the course of N-acetylcysteine therapy from 72 hours to 24 or 36 hours. This shorter regimen offers important benefits for both the patient and the patient's family, such as increased drug tolerability and reduced hospital stay. Patients who intentionally ingested acetaminophen with harmful intent could receive appropriate psychosocial treatment more quickly. In addition, shorter courses of N-acetylcysteine therapy have positive financial ramifications by reducing the hospital stay by 1 or 2 days. Clearly, a shorter treatment regimen would not be appropriate for all patients, particularly those who seek treatment late (> 24 hrs after ingestion) and those with evidence of organ toxicity. In order to provide the necessary evidence to support a change in accepted clinical practice, further investigation on the safety and efficacy of a shorter N-acetylcysteine regimen should be conducted by clinical researchers in a controlled manner.

Stability and microbiology of inhalant N-acetylcysteine used as an intravenous solution for the treatment of acetaminophen poisoning

STUDY OBJECTIVE

Intravenous N-acetylcysteine has been used as an antidote for acetaminophen poisoning for more than 25 years in Europe and Canada. In the United States, only the oral administration of N-acetylcysteine is approved by the US Food and Drug Administration. Many physicians routinely use the inhalant preparation as an intravenous formulation; however, no stability, microbiology, or pyrogen studies have been performed. In this study, we evaluate the stability and microbiology of inhalational N-acetylcysteine compounded as an intravenous formulation.

METHODS

A total of 8 N-acetylcysteine solutions (solution A through H) were prepared by injecting 150 mL of 20% solution through a 22-microm filter to 1 L of 5% dextrose (D(5)W; 2.6% solution). Solutions A through C were prepared at ambient conditions (25 degrees C [77 degrees F], 65% relative humidity), and solution D was prepared at accelerated conditions (40 degrees C [104 degrees F], 75% relative humidity) for stability testing. The assays were performed by means of high-performance liquid chromatography at 0, 4, 8, 12, 24, 36, 48, 60, and 72 hours according to US Pharmacopeia XXIV methodology. Solutions E through G were assessed for bacterial growth, and solution H underwent pyrogen testing by using a Limulus amebocyte lysate method.

RESULTS

Solutions A through C remained stable for at least 60 hours (<10% decomposition), but at 72 hours, there was a 10.3%, 14.9%, and 13.4% degradation, respectively. Under accelerated conditions (solution D), stability lasted for more than 72 hours. Solutions E through G remained free from bacterial growth at 72 hours, and solution H tested negative for endotoxins-pyrogens.

CONCLUSION

Inhalational N-acetylcysteine prepared as an intravenous solution meets US Pharmacopeia standards for stability up to 60 hours and is free from bacteria and their byproducts, offering a viable alternative to the traditional use of oral N-acetylcysteine.

Fulminant liver disease

Fulminant liver disease, acute liver failure (ALF), is one of the most intriguing and challenging conditions in the entire field of internal medicine. ALF is defined as the onset of hepatic encephalopathy and coagulopathy in patients with no known underlying liver disease within 8 to 26 weeks of onset of illness. Many cases develop within a few days, dramatically transforming an otherwise healthy individual to a patient with a high risk for developing multi-organ failure and death.

Predictors of outcome after acetaminophen poisoning in children and adolescents

OBJECTIVE

Shortened courses of N-acetylcysteine may be acceptable in patients with acetaminophen poisoning who are at low risk for toxicity. The goal of this study was to determine which clinical findings best identified patients at lowest risk for acetaminophen-related hepatotoxicity after an acute overdose.

STUDY DESIGN

This was a retrospective analysis, throughout 10 years, of hospital admissions for acute acetaminophen poisoning, with inclusion criteria being an acetaminophen concentration above the possible toxicity line by nomogram, arrival within 24 hours, and an initial prothrombin time (PT), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) measured within 24 hours of ingestion. Clinical parameters capable of identifying patients most and least likely to have hepatotoxicity were evaluated by using sensitivity and specificity testing.

RESULTS

Of 95 patient charts identified, 41 met all inclusion criteria, with 16 patients having hepatotoxicity. PT, AST, and ALT within the first 24 hours postingestion did not identify all patients who had hepatotoxicity. The best predictor of a low risk of toxicity was the presence of normal values for the PT, AST, or ALT within 48 hours of ingestion.

CONCLUSIONS

These data suggest that all patients with an acute acetaminophen overdose should be observed and treated for at least 48 hours postingestion.

S-adenosyl-L-methionine (SAMe) for the treatment of acetaminophen toxicity in a dog

An 8-month-old, spayed female Shetland sheepdog presented 48 hours after ingesting acetaminophen (1 gm/kg body weight). On presentation, the dog was laterally recumbent and hypovolemic. The dog had brown mucous membranes, severe Heinz-body hemolytic anemia, bleeding tendencies, and a red blood cell (RBC) glutathione (GSH) concentration that was 10% of reference values, despite a regenerative erythroid response. Treatment with s-adenosyl-l-methionine (SAMe) as a GSH donor successfully rescued this dog, despite the animal's late presentation after drug ingestion. A loading dose (40 mg/kg body weight) of a stable SAMe salt per os was followed by a maintenance dose (20 mg/kg body weight) sid for 7 days. Additional therapeutic interventions included an intravenous (i.v.) infusion of one unit of packed RBCs (on admission), i.v. fluid support (3 days), and famotidine (7 days) to reduce gastric acidity. Sequential assessment of RBC GSH concentrations and RBC morphology documented response to antidote administration within 72 hours. This case suggests that SAMe may provide a therapeutic option for treatment of acetaminophen toxicosis in dogs capable of retaining an orally administered antidote and maintaining adequate hepatic function for metabolism of SAMe to its thiol substrates.

Alcohol exposure and paracetamol-induced hepatotoxicity

Most instances of hepatotoxicity due to paracetamol in the United Kingdom and Australia are the result of large overdoses of the drug taken with suicidal or parasuicidal intent. In contrast, serious hepatotoxicity at recommended or near-recommended doses for therapeutic purposes has been reported, mainly from the United States and in association with chronic alcohol use, leading to the widely held belief that chronic alcoholics are predisposed to paracetamol-related toxicity at relatively low doses. Yet the effects of alcohol on paracetamol metabolism are complex. Studies performed in both experimental animals and humans indicate that chronic alcohol use leads to a short-term, two- to threefold increase in hepatic content of cytochrome P4502E1, the major isoform responsible for the generation of the toxic metabolite from paracetamol, although increased oxidative metabolism of paracetamol at recommended doses has not been demonstrated clinically. A reduced hepatic content of glutathione, required to detoxify the reactive metabolite, has been documented in chronic alcoholics, due probably to associated fasting and malnutrition, providing a metabolic basis for any possible predisposition of this group to hepatotoxicity at relatively low paracetamol doses. Simultaneous alcohol and paracetamol ingestion reduces oxidative metabolism of paracetamol in both rodents and humans, predominantly as a consequence of depletion in cytosol of free NADPH. The possibilities that chronic alcohol use may predispose to paracetamol-related hepatotoxicity and that alcohol taken with paracetamol may protect against it, based on these metabolic observations, are examined in this review.

Influence of acute and chronic alcohol intake on the clinical course and outcome in acetaminophen overdose

BACKGROUND

Animal studies on acetaminophen toxicity suggest that chronic alcohol intake affects the outcome adversely, whereas acute alcohol intake seems protective. Few clinical data are available.

METHODS

We studied 209 consecutive patients with single-dose acetaminophen overdose. The combined influence of independent variables (gender, age, dose, delay to antidote treatment, chronic and acute alcohol intake and nomogram risk group) on dependent variables (death, development of hepatic encephalopathy and biochemical liver markers) was studied using multiple or logistic regression analysis.

RESULTS

Fifty-seven (27.3%) patients had chronic alcohol intake and 45 (21.5%) patients had acute alcohol intake. Forty-four (21.1%) patients developed hepatic coma and 20 (43.5%) of these patients died. Chronic alcohol intake was significantly and independently associated with the development of hepatic coma, with a lower prothrombin index, lower platelet count, higher creatinine and higher bilirubin. The relative risks for hepatic coma and death were 5.3 (95% confidence interval, 2.2-12.4) and 1.4 (95% confidence interval, 0.5-3.9), respectively, in the chronic alcohol intake group compared with the no chronic alcohol intake group. Acute alcohol intake was not significantly associated with any of the dependent variables studied.

CONCLUSIONS

Chronic alcohol intake enhances acetaminophen hepatotoxicity, whereas acute alcohol intake does not affect the clinical course.

Treatment strategies for early presenting acetaminophen overdose: a survey of medical directors of poison centers in North America and Europe

BACKGROUND

Acetaminophen is frequently used in self-poisoning in Western countries. Although treatment with N-acetylcysteine (NAC) reduces liver injury, no consensus exists on the preferred management of acetaminophen toxicity.

OBJECTIVES

To describe the approach taken by toxicologists in North America and Europe toward the management of acetaminophen toxicity.

METHODS

Medical directors of poison centers in the US, Canada, and Europe were surveyed by means of a questionnaire presenting two clinical scenarios of acetaminophen overdose: a healthy adolescent with no risk factors who had an acute ingestion of acetaminophen, and an adult with both acute ingestion and possible risk factors. For each case, several questions about the management of these patients were asked.

RESULTS

Questionnaires were sent to medical directors of 76 poison centers in North America and 48 in Europe, with response rates of 62% and 44%, respectively. Forty percent of responders suggested using charcoal 4 hours after ingestion of a potential toxic dose of acetaminophen, and 90% recommended treatment with NAC when levels were above 150 microg/mL but below 200 microg/mL 4 hours after ingestion. Duration of treatment with oral NAC ranged from 24 to 96 hours; 38 responders suggested a duration of 72 hours. Of 49 centers recommending oral NAC, 18 (36.7%) said they might consider treatment for less than 72 hours. Eleven of 29 (37.9%) responders suggested treatment with intravenous NAC for more than 20 hours as their usual protocol or a protocol for specific circumstances.

CONCLUSIONS

Our study showed large variability in the management of acetaminophen overdose. Variations in treatment protocols should be addressed in clinical trials to optimize the treatment for this common problem.

Management of paracetamol overdose: current controversies

Paracetamol (acetaminophen) is one of the most frequently used analgesics, and is the most commonly used substance in self-poisoning in the US and UK. Paracetamol toxicity is manifested primarily in the liver. Treatment with N-acetyl-cysteine (NAC), if started within 10 hours from ingestion, can prevent hepatic damage in most cases. Pharmacokinetic data relating plasma paracetamol concentration to time after ingestion have been used to generate a 'probable hepatoxicity line' to predict which cases of paracetamol overdose will result in hepatotoxicity and should be treated with NAC. However, later studies use a 25% lower line as their 'possible hepatotoxicity line'. Although adopting the original line may save considerable resources, further studies are needed to determine whether such an approach is safe. On the basis of the metabolism of paracetamol, several risk factors for paracetamol toxicity have been proposed. These risk factors include long term alcohol (ethanol) ingestion, fasting and treatment with drugs that induce the cytochrome P450 2E1 enzyme system. Although some studies have suggested that these risk factors may be associated with worse prognosis, the data are inconclusive. However, until further evidence is available, we suggest that the lower line should be used when risk factors are present. In Canada and the UK, the intravenous regimen for NAC is used almost exclusively; in the US, an oral regimen is used. Both regimens have been shown to be effective. There is no large scale study with direct comparison between these 2 therapeutic protocols and controversy still exists as to which regimen is superior. During the last few years there has been an increase in the number of reports of liver failure associated with prolonged paracetamol administration for therapeutic reasons. The true incidence of this phenomenon is not known. We suggest testing liver enzyme levels if a child has received more than 75 mg/kg/day of paracetamol for more than 24 hours during febrile illness, and to treat with NAC when transaminase levels are elevated. Paracetamol overdose during pregnancy should be treated with either oral or intravenous NAC according to the regular protocols in order to prevent maternal, and potentially fetal, toxicity. Unless severe maternal toxicity develops, paracetamol overdose does not appear to increase the risk for adverse pregnancy outcome.

Interventions for paracetamol (acetaminophen) overdoses

BACKGROUND

Self-poisoning with paracetamol (acetaminophen) is a common cause of hepatotoxicity in the Western World. Interventions for paracetamol poisoning encompass inhibition of absorption, removal from the vascular system, antidotes, and liver transplantation.

OBJECTIVES

The objective was to assess the beneficial and harmful effects of interventions or combination of interventions for paracetamol overdose.

SEARCH STRATEGY

The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Library, MEDLINE, EMBASE, and text searches were combined (until July 2001).

SELECTION CRITERIA

Randomised clinical trials (RCTs) and observational studies as well as human volunteer randomised trials were included. The studies could be unpublished or published as an article, an abstract, or a letter and no language limitations were applied.

DATA COLLECTION AND ANALYSIS

All the analyses were performed according to the intention to treat. The methodological quality of the included trials was evaluated by components of methodological quality.

MAIN RESULTS

Nine RCTs (all small and of low methodological quality), one quasi-randomised trials, 37 observational studies, and nine randomised trials including human volunteers were identified. It was impossible to perform meta-analyses including more than two RCTs. Activated charcoal, gastric lavage, and ipecacuanha are able to reduce the absorption of paracetamol but the clinical benefit is unclear. Of these, activated charcoal seems to have the best risk-benefit ratio. N-acetylcysteine seems preferable to placebo/supportive treatment (relative risk of mortality in patients with fulminant hepatic failure = 0.65; 95% confidence interval 0.43 to 0.99), dimercaprol, and cysteamine, but N-acetylcysteine's superiority to methionine is unproven. It is not clear which N-acetylcysteine treatment protocol offers the best efficacy. No evidence supports haemoperfusion or cimetidine for paracetamol overdose. Liver transplantation has the potential to be life saving in fulminant hepatic failure, but further refinement of selection criteria for liver transplantation and evaluation of the long-term outcome are required.

REVIEWER'S CONCLUSIONS

This systematic Review has highlighted a paucity of RCTs on interventions for paracetamol overdose. Activated charcoal seems the best choice to reduce paracetamol absorption. N-acetylcysteine should be given to patients with paracetamol overdose. No N-acetylcysteine regime has been shown to be more effective than any other. It is a delicate balance when to proceed to liver transplantation, which may be life saving in patients with a poor prognosis. Interventions for paracetamol overdose need assessment in high-quality, multi-centre RCTs.

Comparison of the therapeutic efficacy of 4-methylpyrazole and N-acetylcysteine on acetaminophen (paracetamol) hepatotoxicity in rats

Obtaining effective analgesia with a minimal erosive effect on gastric mucosal tissue has increased the consumption of acetaminophen (paracetamol), especially among the elderly. However, the hepatotoxic effects of acetaminophen have also increased. We aimed to compare the effects of 4-methylpyrazole (4-MP), N-acetylcysteine (NAC) and their combined use on the hepatotoxicity of acetaminophen in a rat model. Male Wistar Albino rats were divided into six groups. Groups 1-5 received 2,000 mg/kg acetaminophen by gavage while the control group was group 6. Group 2 animals were given NAC (loading dose 140 mg/kg followed by seven doses at 4 h intervals); group 3 received 50 mg/kg 4-MP; group 4 received 200mg/kg 4-MP; and group 5 received NAC as in group 2 plus 200 mg/kg 4-MP. Blood samples were taken for measurements of serum AST and ALT levels. The livers of the rats were removed for microscopic examination and grading of hepatic necrosis. AST and ALT levels in groups 2-5 were lower than that of group 1 (p < 0.001), although no significant difference was noted between groups 2-5 (p > 0.05). Higher levels of ALT were found in group 5 than in group 2 (p < 0.05), and higher levels of AST were found in group 5 than in group 3 (p < 0.01). Median necrosis scores were 3.36 for rats receiving acetaminophen alone (p < 0.001, compared with groups 2-6), 1.45-1.81 for groups 2-5 (p > 0.05, compared with each other), and 0.18 for control rats (p < 0.001, compared with groups 1-5). In conclusion, the administration of 4-MP and/or NAC after 4 h of administering toxic dose of acetaminophen, inhibits hepatotoxicity in rats. There was no difference between the 4-MP and NAC-treated groups as reflected by comparable levels of serum transaminases and the degree of hepatic necrosis. Combining of 4-MP and NAC offers no benefit.

Interaction between N-acetylcysteine and activated charcoal: implications for the treatment of acetaminophen poisoning

STUDY OBJECTIVE

To determine if the presence of N-acetylcysteine reduces the ability of activated charcoal to adsorb acetaminophen both in the absence and presence of a coingestant.

DESIGN

In vitro laboratory study.

SETTING

University hospital research laboratory.

MEASUREMENTS AND MAIN RESULTS

The adsorption of acetaminophen and salicylic acid by activated charcoal in the presence and absence of N-acetylcysteine was measured in vitro. Acetaminophen and salicylic acid analyses were conducted with high-performance liquid chromatography. Adsorption data were compared using the appropriate parametric statistical test. The addition of N-acetylcysteine significantly decreased the binding of acetaminophen by activated charcoal (p<0.005). When salicylic acid was added to simulate a coingestant, N-acetylcysteine significantly decreased salicylate adsorption by charcoal (p<0.001).

CONCLUSIONS

The presence of N-acetylcysteine reduces the ability of activated charcoal to adsorb acetaminophen and coingestants. In vivo data will be required to determine the clinical relevance of these interactions.

Emergency department observation for toxicologic exposures

Most toxicologic exposures resolve within 24 hours, yet catastrophic outcomes may occur if patients are directly discharged from the emergency department (ED). These cases are, perhaps, the ideal candidates for observation unit (OU) management. This article reviews the criteria for admission and discharge as well as clinical management strategies in the OU for the most common toxicologic exposures. Special attention is given to the multidisciplinary interactions among the ED physician, the medical toxicologist, the physiatrist, and the specialty laboratory.

Management of drug-induced liver disease

The treatment and prevention of drug-induced liver injury starts with the recognition of hepatotoxicity at the earliest possible time so that the suspected drug can be discontinued expeditiously. Both liver enzyme monitoring and vigilance for signs of hypersensitivity involving the liver are useful strategies for many agents known to cause hepatocellular necrosis leading to liver failure. Specific antidotes to prevent or limit hepatic damage exist for only a few drugs, the most important being N-acetylcysteine for the treatment of acetaminophen hepatotoxicity. Corticosteroids are of unproven benefit in the setting of fulminant failure. Ursodiol may be helpful in instances of cholestatic injury. For other agents, supportive measures and the increasing use of liver-assist devices as well as emergency liver transplantation are available when drug injury evolves into irreversible liver failure. It is hoped that a better understanding of hepatotoxicity mechanisms will lead to the development of more specific and effective forms of therapy in the near future.