A prospective evaluation of the effect of activated charcoal before oral N-acetylcysteine in acetaminophen overdose

Systematic review on the use of activated charcoal for gastrointestinal decontamination following acute oral overdose

INTRODUCTION

The use of activated charcoal in poisoning remains both a pillar of modern toxicology and a source of debate. Following the publication of the joint position statements on the use of single-dose and multiple-dose activated charcoal by the American Academy of Clinical Toxicology and the European Association of Poison Centres and Clinical Toxicologists, the routine use of activated charcoal declined. Over subsequent years, many new pharmaceuticals became available in modified or alternative-release formulations and additional data on gastric emptying time in poisoning was published, challenging previous assumptions about absorption kinetics. The American Academy of Clinical Toxicology, the European Association of Poison Centres and Clinical Toxicologists and the Asia Pacific Association of Medical Toxicology founded the Clinical Toxicology Recommendations Collaborative to create a framework for evidence-based recommendations for the management of poisoned patients. The activated charcoal workgroup of the Clinical Toxicology Recommendations Collaborative was tasked with reviewing systematically the evidence pertaining to the use of activated charcoal in poisoning in order to update the previous recommendations.

OBJECTIVES

The main objective was: Does oral activated charcoal given to adults or children prevent toxicity or improve clinical outcome and survival of poisoned patients compared to those who do not receive charcoal?  Secondary objectives were to evaluate pharmacokinetic outcomes, the role of cathartics, and adverse events to charcoal administration. This systematic review summarizes the available evidence on the efficacy of activated charcoal.

METHODS

A medical librarian created a systematic search strategy for Medline (Ovid), subsequently translated for Embase (via Ovid), CINAHL (via EBSCO), BIOSIS Previews (via Ovid), Web of Science, Scopus, and the Cochrane Library/DARE. All databases were searched from inception to December 31, 2019. There were no language limitations.  One author screened all citations identified in the search based on predefined inclusion/exclusion criteria. Excluded citations were confirmed by an additional author and remaining articles were obtained in full text and evaluated by at least two authors for inclusion. All authors cross-referenced full-text articles to identify articles missed in the searches. Data from included articles were extracted by the authors on a standardized spreadsheet and two authors used the GRADE methodology to independently assess the quality and risk of bias of each included study.

RESULTS

From 22,950 titles originally identified, the final data set consisted of 296 human studies, 118 animal studies, and 145 in vitro studies. Also included were 71 human and two animal studies that reported adverse events. The quality was judged to have a Low or Very Low GRADE in 469 (83%) of the studies. Ninety studies were judged to be of Moderate or High GRADE. The higher GRADE studies reported on the following drugs: paracetamol (acetaminophen), phenobarbital, carbamazepine, cardiac glycosides (digoxin and oleander), ethanol, iron, salicylates, theophylline, tricyclic antidepressants, and valproate. Data on newer pharmaceuticals not reviewed in the previous American Academy of Clinical Toxicology/European Association of Poison Centres and Clinical Toxicologists statements such as quetiapine, olanzapine, citalopram, and Factor Xa inhibitors were included. No studies on the optimal dosing for either single-dose or multiple-dose activated charcoal were found. In the reviewed clinical data, the time of administration of the first dose of charcoal was beyond one hour in 97% (n = 1006 individuals), beyond two hours in 36% (n = 491 individuals), and beyond 12 h in 4% (n = 43 individuals) whereas the timing of the first dose in controlled studies was within one hour of ingestion in 48% (n = 2359 individuals) and beyond two hours in 36% (n = 484) of individuals.

CONCLUSIONS

This systematic review found heterogenous data. The higher GRADE data was focused on a few select poisonings, while studies that addressed patients with unknown and or mixed ingestions were hampered by low rates of clinically meaningful toxicity or death.  Despite these limitations, they reported a benefit of activated charcoal beyond one hour in many clinical scenarios.

Liver injury induced by paracetamol and challenges associated with intentional and unintentional use

Drug induced liver injury (DILI) is a common cause of acute liver injury. Paracetamol, also known as acetaminophen, is a widely used anti-pyretic that has long been established to cause liver toxicity once above therapeutic levels. Hepatotoxicity from paracetamol overdose, whether intentional or non-intentional, is the most common cause of DILI in the United States and remains a global issue. Given the increased prevalence of combination medications in the form of pain relievers and antihistamines, paracetamol can be difficult to identify and remains a significant cause of acute hepatotoxicity, as evidenced by its contribution to over half of all acute liver failure cases in the United States. This is especially concerning given that, when co-ingested with other medications, the rise in serum paracetamol levels may be delayed past the 4-hour post-ingestion mark that is currently used to determine patients that require medical therapy. This review serves to describe the clinical and pathophysiologic features of hepatotoxicity secondary to paracetamol and provide an update on current available knowledge and treatment options.

Should N-Acetylcysteine be Administered Orally or Intravenously for the Treatment of Paracetamol Overdose?

Introduction

Paracetamol is the most commonly used drug in deliberate poisoning. N-acetylcysteine is the standard antidote for significant acute paracetamol overdose, but the route of administration varies between countries. This review aimed to find and appraise those comparative studies which would help answer the following question: in patients who have taken an overdose of paracetamol requiring antidote, is there any difference between intravenous and oral N-acetylcysteine in mortality, hepatotoxicity, adverse drug reactions or cost?

Methods

A literature search was conducted using Medline and other databases. Relevant papers were identified and appraised.

Results

One animal study and seven comparative clinical studies were identified and appraised. The quality of the evidence was generally poor, and there was no clear difference in outcomes between the two routes of administration.

Conclusions

Without evidence of advantage for one route over the other, routine practice should not be changed. However, after 30 years experience, both routes appear to be effective and safe, and in countries where intravenous administration is the standard, it would be reasonable to consider the oral route as an alternative when intravenous access is problematic. There is a need for prospective, randomised trials to determine the relative effectiveness, safety and cost of intravenous and oral formulations of N-acetylcysteine.

Management of Acute Hepatotoxicity Including Medical Agents and Liver Support Systems

Drug-induced liver injury (DILI) can be predictable or idiosyncratic and has an estimated incidence of approximately 20 cases per 100,000 persons per year. DILI is a common cause of acute liver failure in the United States. No accurate tests for diagnosing DILI exist, and its diagnosis is based on exclusion of other conditions. Managing DILI includes discontinuing the suspected causative agent and in selected cases administering an antidote. Liver support systems are used for long-term support or as a bridge to transplantation and are effective for improving encephalopathy, hyperbilirubinemia, and other liver-related conditions, but whether they improve survival remains uncertain.

Adsorption of Biologically Active Compounds from Aqueous Solutions on to Commercial Unmodified Activated Carbons. Part IV. Do the Properties of Amphoteric Carbon Surface Layers Influence the Adsorption of Paracetamol at Acidic pH Levels?

Three previously characterised, unmodified commercial activated carbons (D43/1, WD and AHD), differing in porosity and surface layer composition, were further examined using some additional methods of surface chemical description (electrochemical studies, acid–base site distribution, pHPZC and resistance measurements). Paracetamol adsorption isotherms (as well as kinetic curves) were measured on these carbons at acidic pH (1.5) and three temperatures, i.e. 300, 310 and 320 K. Measurements of the enthalpies of immersion in HCl and paracetamol solutions were also performed at 310 K, and diffusion coefficients and energies calculated.

The results of measurements at acidic pH were compared with those obtained under neutral pH conditions. Some new correlations between the properties of the carbon surface and the constants characterising the process of paracetamol adsorption suggested recently were extended from data measured initially for six carbons. The mechanism of adsorption at both pH values was elaborated with the importance of surface carbonyls and basic groups being emphasised. The adsorption of the polymerisation product of paracetamol at acidic pH was determined using FT-IR and UV–vis spectroscopic measurements.

Hepatic Failure

The progression of liver disease can cause several physiologic derangements that may precipitate hepatic failure and require admission to an intensive care unit. The underlying pathology may be acute, acute-on chronic, or chronic in nature. Liver failure may manifest with a variety of clinical signs and symptoms that need prompt attention. The compromised synthetic and metabolic activity of the failing liver affects all organ systems, from neurologic to integumentary. Supportive care and specific therapies should be instituted in order to improve outcome and minimize time of recovery.

In this chapter we will discuss the definition, clinical manifestations, workup, and management of acute and chronic liver failure and the general principles of treatment of these patients. Management of liver failure secondary to certain common etiologies will also be presented. Finally, liver transplantation and alternative therapies will also be discussed.

Management of hepatic encephalopathy

OPINION STATEMENT

Hepatic encephalopathy management varies depending on the acuity of liver failure. However, in patients with either acute or chronic liver failure five basic steps in management are critical: stabilization, addressing modifiable precipitating factors, lowering blood ammonia, managing elevated intracranial pressure (ICP) (if present), and managing complications of liver failure that can contribute to encephalopathy, particularly hyponatremia. Because liver failure patients are prone to a variety of other medical problems that can lead to encephalopathy (such as coagulopathy associated intracranial hemorrhage, electrolyte disarray, renal failure, hypotension, hypoglycemia, and infection), a thorough history, physical and neurologic examination is mandated in all encephalopathic liver failure patients. There should be a low threshold for brain imaging in patients with focal neurological deficits given the propensity for spontaneous intracranial hemorrhage. In patients with acute liver failure and high grade encephalopathy, identification of the etiology of acute liver failure is essential to guide treatment and antidote administration, particularly in the case of acetaminophen poisoning. Equally critical is management of elevated ICP in acute liver failure. Intracranial hypertension can be treated with hypertonic saline and/or adjustment of the dialysis bath. Placement of an intracranial monitor to guide ICP therapy is risky because of concomitant coagulopathy and remains controversial. Continuous renal replacement therapy may help lower serum ammonia, treat coexisting uremia, and improve symptoms. Liver transplantation is the definitive treatment for patients with acute liver failure and hepatic encephalopathy. In patients with chronic hepatic encephalopathy, lactulose and rifaxamin remain a mainstay of therapy. In these patients, it is essential to identify reversible causes of hepatic encephalopathy such as increased ammonia production and/or decreased clearance (eg, infection, GI bleed, constipation, hypokalemia, dehydration). Chronic hyponatremia should be managed by gradual sodium correction of no more than 8‒12 meq/L per day to avoid central myelinolysis syndrome. Free water restriction and increased dietary sodium are reasonable, cost effective treatment options. Many emerging therapies, both pharmacologic and interventional, are currently being studied to improve management of hepatic encephalopathy.

Acetaminophen-related hepatotoxicity

Acetaminophen (APAP) is the leading worldwide cause of drug overdose and acute liver failure (ALF). Single overdose ingestion and therapeutic misadventure may cause hepatotoxicity. Several factors, such as concomitant alcohol use or abuse, concurrent medications, genetic factors, and nutritional status, can influence the susceptibility and severity of APAP hepatotoxicity. Early manifestations of APAP hepatotoxicity are nonspecific, but require prompt recognition by physicians. Patients with repeated overdose tend to present late, and in such hepatotoxicity may have already evolved. N-acetylcysteine is a very effective antidote when giving within 8 hours, and is also recommended after a presentation of hepatotoxicity and ALF. The prognosis of patients with APAP-induced ALF is better than other causes of ALF. Liver transplantation should be offered to those who are unlikely to survive.

Oral and Intravenous Acetylcysteine for Treatment of Acetaminophen Toxicity: A Systematic Review and Meta-analysis

INTRODUCTION

There are few reports summarizing the effectiveness of oral and intravenous (IV) acetylcysteine. We determined the proportion of acetaminophen poisoned patients who develop hepatotoxicity (serum transaminase > 1000 IU/L) when treated with oral and IV acetylcysteine.

METHODS

Studies were double abstracted by trained researchers. We determined the proportions of patients who developed hepatotoxicity for each route using a random effects model. Studies were further stratified by early and late treatment.

RESULTS

We screened 4,416 abstracts; 16 articles, including 5,164 patients, were included in the meta-analysis. The overall rate of hepatotoxicity for the oral and IV routes were 12.6% and 13.2%, respectively. Treatment delays are associated with a higher rate of hepatotoxicity.

CONCLUSION

Studies report similar rates of hepatotoxicity for oral and IV acetylcysteine, but direct comparisons are lacking. While it is difficult to disentangle the effects of dose and duration from route, our findings suggest that the rates of hepatotoxicity are similar for oral and IV administration.

A review of acetaminophen poisoning

Acetaminophen poisoning remains one of the more common drugs taken in overdose with potentially fatal consequences. Early recognition and prompt treatment with N-acetylcysteine can prevent hepatic injury. With acute overdose, the Rumack-Matthew nomogram is a useful tool to assess risk and guide management. Equally common to acute overdose is the repeated use of excessive amounts of acetaminophen. Simultaneous ingestion of several different acetaminophen-containing products may result in excessive dosage. These patients also benefit from N-acetylcysteine. Standard courses of N-acetylcysteine may need to be extended in patients with persistently elevated plasma concentrations of acetaminophen or with signs of hepatic injury.

Toxicology in the critical care unit

Toxicologic conditions are encountered in critically ill patients due to intentional or unintentional misuse of or exposure to therapeutic or illicit drugs. Additionally, toxicities related to medical interventions may develop in hospitalized patients. This review focuses on recent developments in the field of critical care toxicology. Early interventions to decrease absorption or enhance elimination of toxins have limited value. Specific interventions to manage toxicities due to analgesics, sedative-hypnotics, antidepressants, antipsychotics, cardiovascular agents, alcohols, carbon monoxide, and cholinergic agents are reviewed. Hospital-acquired toxicities due to methemoglobinemia, propylene glycol, and propofol should be recognized and treated. The clinician is continually required to incorporate clinical judgment along with available scientific data and clinical evidence to determine the best therapy for toxicologic conditions.

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 th 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.

The effect of yogurt on acetaminophen absorption by activated charcoal and burnt toast

Although acetaminophen overdose can be treated with N-acetylcysteine, activated charcoal is useful in preventing absorption of acetaminophen from the gut. Mixing activated charcoal with yogurt may make the dose more palatable. We investigated effects of yogurt on absorption of acetaminophen by burnt toast or activated charcoal in intestinal fluid using an in vitro model. The aliquots of phosphate buffer saline (PBS) were supplemented with high concentrations of acetaminophen after adjusting the pH to 7.2 (to mimic intestinal fluid). Then specimens were treated with various dosages (15 mg/mL, 25 mg/mL, or 50 mg/mL) of activated charcoal or burnt toast. A small amount of fluid was withdrawn at 0, 5, 10, 20, and 30 min and acetaminophen concentrations were measured by the fluorescence polarization immunoassay (FPIA). We also treated other aliquots of PBS buffer containing acetaminophen with activated charcoal and yogurt or burnt toast and yogurt. Then small aliquots were withdrawn at specific time intervals to determine concentrations of acetaminophen. Activated charcoal was very effective in removing acetaminophen from intestinal fluids and the presence of yogurt insignificantly affected such absorptions. In contrast, burnt toast had a modest effect on removing acetaminophen from fluids but yogurt significantly increased the capability of burnt toast to absorb acetaminophen. However, the activated charcoal/yogurt combination is more effective than the burnt toast/yogurt combination for absorbing acetaminophen.

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 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.

Impact of Activated Charcoal After Acute Acetaminophen Overdoses Treated with N-Acetylcysteine

Previous studies have suggested that patients receiving both activated charcoal (AC) and N-acetylcysteine (NAC) after acute acetaminophen (APAP) overdoses may have improved outcomes. We evaluated all acute acetaminophen overdoses that received NAC therapy reported to US poison centers for the years 1993 through 2004. Groups were separated based on therapy received: 1) both AC and NAC and 2) NAC alone. There were 97,960 acetaminophen overdoses reported, with 49,427 patients (50%) receiving NAC and AC. Reports of AST/ALT > 1000, a major effect, and death were 1301 (2.9%), 2957 (6.6%), and 232 (0.5%), respectively, for patients receiving NAC plus AC, vs. 5273 (12%), 4534 (10.3%), and 369 (0.8%), respectively, for patients receiving NAC alone (p < 0.01). Use of Toxic Exposure Surveillance System data in the present study has a number of limitations, including its retrospective nature and no documentation of when NAC therapy was initiated. It is possible that those patients who did not receive AC presented to the Emergency Department later in their overdose and had NAC therapy initiated later, and therefore they were predisposed to a greater risk of hepatic injury. Evaluation of 12 years of acute APAP overdoses suggests that the use of AC, in addition to NAC therapy, may provide improved patient outcomes.

Activated charcoal for pediatric poisonings: the universal antidote?

PURPOSE OF REVIEW

For decades, activated charcoal has been used as a 'universal antidote' for the majority of poisons because of its ability to prevent the absorption of most toxic agents from the gastrointestinal tract and enhance the elimination of some agents already absorbed. This manuscript will review the history of activated charcoal, its indications, contraindications, and the complications associated with its use as reported in the literature.

RECENT FINDINGS

Recent randomized prospective studies, although with small numbers, have shown no difference in length of hospital stay, morbidity, and mortality between groups who received and did not receive activated charcoal. No study has had sufficient numbers to satisfactorily address clinical outcome in patients who received activated charcoal less than 1 h following ingestion.

SUMMARY

If used appropriately, activated charcoal has relatively low morbidity. Due to the lack of definitive studies showing a benefit in clinical outcome, it should not be used routinely in ingestions. AC could be considered for patients with an intact airway who present soon after ingestion of a toxic or life-threatening dose of an adsorbable toxin. The appropriate use of activated charcoal should be determined by the analysis of the relative risks and benefits of its use in each specific clinical scenario.

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.

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: an evidence-based consensus guideline for out-of-hospital management

The objective of this guideline is to assist poison center personnel in the appropriate out-of-hospital triage and initial management of patients with suspected ingestions of acetaminophen. An evidence-based expert consensus process was used to create this guideline. This guideline applies to ingestion of acetaminophen alone and is based on an assessment of current scientific and clinical information. The expert consensus panel recognizes that specific patient care decisions may be at variance with this guideline and are the prerogative of the patient and the health professionals providing care. The panel's recommendations follow. These recommendations are provided in chronological order of likely clinical use. The grade of recommendation is provided in parentheses. 1) The initial history obtained by the specialist in poison information should include the patient's age and intent (Grade B), the specific formulation and dose of acetaminophen, the ingestion pattern (single or multiple), duration of ingestion (Grade B), and concomitant medications that might have been ingested (Grade D). 2) Any patient with stated or suspected self-harm or who is the recipient of a potentially malicious administration of acetaminophen should be referred to an emergency department immediately regardless of the amount ingested. This referral should be guided by local poison center procedures (Grade D). 3) Activated charcoal can be considered if local poison center policies support its prehospital use, a toxic dose of acetaminophen has been taken, and fewer than 2 hours have elapsed since the ingestion (Grade A). Gastrointestinal decontamination could be particularly important if acetylcysteine cannot be administered within 8 hours of ingestion. Acute, single, unintentional ingestion of acetaminophen: 1) Any patient with signs consistent with acetaminophen poisoning (e.g., repeated vomiting, abdominal tenderness in the right upper quadrant or mental status changes) should be referred to an emergency department for evaluation (Grade D). 2) Patients less than 6 years of age should be referred to an emergency department if the estimated acute ingestion amount is unknown or is 200 mg/kg or more. Patients can be observed at home if the dose ingested is less than 200 mg/kg (Grade B). 3) Patients 6 years of age or older should be referred to an emergency department if they have ingested at least 10 g or 200 mg/kg (whichever is lower) or when the amount ingested is unknown (Grade D). 4) Patients referred to an emergency department should arrive in time to have a stat serum acetaminophen concentration determined at 4 hours after ingestion or as soon as possible thereafter. If the time of ingestion is unknown, the patient should be referred to an emergency department immediately (Grade D). 5) If the initial contact with the poison center occurs more than 36 hours after the ingestion and the patient is well, the patient does not require further evaluation for acetaminophen toxicity (Grade D). Repeated supratherapeutic ingestion of acetaminophen (RSTI): 1) Patients under 6 years of age should be referred to an emergency department immediately if they have ingested: a) 200 mg/kg or more over a single 24-hour period, or b) 150 mg/kg or more per 24-hour period for the preceding 48 hours, or c) 100 mg/kg or more per 24-hour period for the preceding 72 hours or longer (Grade C). 2) Patients 6 years of age or older should be referred to an emergency department if they have ingested: a) at least 10 g or 200 mg/kg (whichever is less) over a single 24-hour period, or b) at least 6 g or 150 mg/kg (whichever is less) per 24-hour period for the preceding 48 hours or longer. In patients with conditions purported to increase susceptibility to acetaminophen toxicity (alcoholism, isoniazid use, prolonged fasting), the dose of acetaminophen considered as RSTI should be greater than 4 g or 100 mg/kg (whichever is less) per day (Grade D). 3) Gastrointestinal decontamination is not needed (Grade D). Other recommendations: 1) The out-of-hospital management of extended-release acetaminophen or multi-drug combination products containing acetaminophen is the same as an ingestion of acetaminophen alone (Grade D). However, the effects of other drugs might require referral to an emergency department in accordance with the poison center's normal triage criteria. 2) The use of cimetidine as an antidote is not recommended (Grade A).

Medicinal Carbon Tablets for Treatment of Acetaminophen Intoxication: Adsorption Characteristics of Medicinal Carbon Powder and Its Tablets

Adsorption characteristics of medicinal carbon powder (JP 14) for acetaminophen were examined at 37 degrees C using conventional incubation in an attempt to obtain an effective oral dosage form. Hydroxypropyl cellulose (HPC) and maltitol (MT), being able to act as a binding agent, were tested as additives. Tablets of medicinal carbon were produced by the wet granulation method. The rate and extent of adsorption of the medicinal carbon powder were roughly similar in water, JP 14 1st fluid (pH 1.2) and JP 14 2nd fluid (pH 6.8). The relationship between concentrations of free and adsorbed acetaminophen indicated that the adsorption followed the Langmuir mode. The maximal adsorption of acetaminophen in water was 0.219 g per gram medicinal carbon powder, little influenced by the addition of MT, but slightly reduced by the addition of HPC. The tablet prepared using MT as a binding agent displayed a favorable hardness and adequate disintegration time. The tablet showed good adsorption potential for acetaminophen, though the adsorption rate and extent of the tablet were reduced to some extent as compared with powder.

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.

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.

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.

Oral or intravenous N-acetylcysteine: which is the treatment of choice for acetaminophen (paracetamol) poisoning?

BACKGROUND

The optimal route and duration of administration for N-acetyl-cysteine in the management of acetaminophen (paracetamol) poisoning are controversial. It has been stated on the basis of a selected post-hoc analysis that oral N-acetylcysteine is superior to intravenous N-acetylcysteine in presentations later than 15 hours.

AIM OF STUDY

To investigate the efficacy of intravenous or oral N-acetylcysteine.

PATIENTS AND METHODS

We analyzed a series of acetaminophen poisonings treated with a protocol including activated charcoal and intravenous N-acetylcysteine. The outcomes assessed included use of N-acetylcysteine, adverse effects of intravenous N-acetylcysteine, and the occurrence of hepatotoxicity (transaminase > 1000 U/L). We incorporated these results in a meta-analysis of previously reported series of acetaminophen poisonings to compare the outcomes from intravenous and oral N-acetylcysteine use.

RESULTS

Of 981 patients admitted over 10 years, 4% (40) presented later than 24 hours and 10% (100) had concentrations of acetaminophen that indicated a probable or high risk of hepatotoxicity. The 30 patients who developed hepatotoxicity presented later, took larger amounts, had higher concentrations, and received N-acetylcysteine later than those who did not. No patients received a liver transplant but 2 patients died (one after referral to a transplant unit and one just before). Adverse reactions to intravenous N-acetylcysteine occurred in 6% (12/205) of patients but none prevented completion of the treatment. In the meta-analysis, those with probable or high risk concentrations had similar outcomes with intravenous (pooled n = 341) and oral N-acetylcysteine (pooled n = 1462) administration. Rates of hepatotoxicity for those treated within 10 hours (3 and 6%), late (10-24 hours: 30 and 26%), and overall (0-24 hours: 16 and 19%) were all similar. The proportion of patients classified as presenting later than 10 hours is much greater in the oral N-acetylcysteine studies (64%) than in many of the intravenous N-acetylcysteine studies (38%, 44%, and 63%).

CONCLUSIONS

The differences claimed between oral and intravenous N-acetylcysteine regimes are probably artifactual and relate to inappropriate subgroup analysis. A shorter hospital stay, patient and doctor convenience, and the concerns over the reduction in bioavailability of oral N-acetylcysteine by charcoal and vomiting make intravenous N-acetylcysteine preferable for most patients with acetaminophen poisoning.

Activated charcoal reduces the need for N-acetylcysteine treatment after acetaminophen (paracetamol) overdose

BACKGROUND

The evidence for efficacy of gastric lavage and activated charcoal for gastrointestinal decontamination in poisoning has relied entirely on volunteer studies and/or pharmacokinetic studies and evidence for any clinical benefits or resource savings is lacking.

AIM OF STUDY

To investigate the value of gastrointestinal decontamination using gastric lavage and/or activated charcoal in acetaminophen (paracetamol) poisoning.

PATIENTS AND METHODS

We analyzed a series of 981 consecutive acetaminophen poisonings. These patients were treated with gastric lavage and activated charcoal, activated charcoal alone, or no gastrointestinal decontamination. The decision as to which treatment was received was determined by patient cooperation, the treating physician, coingested drugs, and time to presentation after the overdose.

RESULTS

Of 981 patients admitted over 10 years, 10% (100) had serum concentrations of acetaminophen that indicated a probable or high risk of hepatotoxicity. The risk of toxic concentrations for patients ingesting less than 10 g of acetaminophen was very low. In patients presenting within 24 hours, who had ingested 10 g or more, those who had been given activated charcoal were significantly less likely to have probable or high risk concentrations (Odds ratio 0.36, 95% CI 0.23-0.58, p < 0.0001). Gastric lavage, in addition to activated charcoal, did not further decrease the risk (Odds ratio 1.12, 95% CI 0.57-2.20, p = 0.86).

CONCLUSIONS

Toxic concentrations of serum acetaminophen (paracetamol) are uncommon in patients ingesting less than 10 g. In those ingesting more, activated charcoal appears to reduce the number of patients who achieve toxic acetaminophen concentrations and thus may reduce the need for treatment and hospital stay.

Paracetamol poisoning in children

Paracetamol (acetaminophen) has become an antipyretic drug of choice. Due to its widespread use, toxicity secondary to overdose has increased in recent years. Children are especially vulnerable to accidental exposure due to non availability of child proof containers in India. The main clinical features of acute toxicity include anorexia, vomiting, abdominal pain, jaundice, hematuria and metabolic acidoses. Diagnosis is based on history and laboratory findings of acidosis and abnormal liver function tests. N-acetylcysteine is the specific antidote. This article reviews in detail the toxicokinetics, pathophysiology, clinical features and management of paracetamol poisoning in children.

Potential time savings by prehospital administration of activated charcoal

OBJECTIVE

Activated charcoal (AC) has been proven useful in many toxic ingestions. Theoretically, administration of AC in the prehospital environment could save valuable time in the treatment of patients who have sustained potentially toxic oral ingestions. The purpose of this study was to determine the frequency of prehospital AC administration and to identify time savings that could potentially result from field AC administration.

METHODS

Adult patients with a chief complaint of toxic ingestion who had complete emergency medical services (EMS) and emergency department (ED) records and no medical treatment (gastric emptying, AC administration) prior to EMS arrival were eligible for inclusion. Data obtained from EMS and ED records included time of EMS departure from the scene, time of EMS arrival at the ED, and time of administration of AC in the ED. Since most EMS agencies in this system do not insert gastric tubes, patients requiring gastric tube placement for administration of AC were excluded.

RESULTS

Twenty-nine of 117 (24.8%) adult patients received oral AC with no other intervention. None of the 117 patients received AC in the prehospital setting. The EMS transport time for these patients ranged from 5 to 43 minutes (mean 16.2 +/- 9.7 minutes). The delay from ED arrival to AC administration ranged from 5 to 94 minutes (mean 48.8 +/- 24.1 minutes), and was more than 60 minutes for 14 (48.2%) of the patients. The total time interval from scene departure to ED AC administration ranged from 17 to 111 minutes (mean 65.0 +/- 25.9 minutes).

CONCLUSIONS

In a selected subset of patients who tolerate oral AC, prehospital administration of AC could result in earlier and potentially more efficacious AC therapy. Prospective study of the benefits and feasibility of prehospital AC administration is indicated.