Effectiveness of delayed activated charcoal administration in simulated paracetamol (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.

Acetaminophen Poisoning

Acetaminophen is a common medication taken in deliberate self-poisoning and unintentional overdose. It is the commonest cause of severe acute liver injury in Western countries. The optimal management of most acetaminophen poisonings is usually straightforward. Patients who present early should be offered activated charcoal and those at risk of acute liver injury should receive acetylcysteine. This approach ensures survival in most. The acetaminophen nomogram is used to assess the need for treatment in acute immediate-release overdoses with a known time of ingestion. However, scenarios that require different management pathways include modified-release, large/massive, and repeated supratherapeutic ingestions.

Novel method to estimate the appropriate dosing interval for activated charcoal to avoid interaction with other drugs

PURPOSE

Activated charcoal is known to adsorb a variety of drugs concomitantly administered and reduce their intestinal absorption, and separating the dosing is considered a practical approach to avoid this drug interaction. The aim of the present study was to develop and validate a simple method to estimate the sufficient dosing interval to avoid drug interaction using the pharmacokinetic profile of the subject drugs administered alone and the amplitude of interaction upon simultaneous administration with activated charcoal.

METHODS

For each subject drug, the pharmacokinetic profile and the amplitude of interaction, as assessed by AUCR (the ratio of area under the plasma concentration-time curve (AUC) in the presence of activated charcoal to that in its absence), were collected from previous reports. The AUCR value was estimated based on the compartment model under the assumption that the subject drug in the first gastrointestinal compartment is immediately adsorbed to a certain extent upon the administration of activated charcoal. The estimated AUCR (AUCR_e) for each drug with certain dosing interval was compared with the respective AUCR value reported previously (AUCR_obs).

RESULTS

Among twenty concentration profiles for 14 subject drugs obtained from previous reports, 15 AUCR_e values fell in the range of 80-120% of the respective AUCR_obs values.

CONCLUSION

The developed method enabled estimation of the amplitude of DDI by activated charcoal administered in a certain dosing interval, whereas overestimation of AUCR_e was observed for drugs that undergo extensive enterohepatic circulation.

Interventions for paracetamol (acetaminophen) overdose

BACKGROUND

Paracetamol (acetaminophen) is the most widely used non-prescription analgesic in the world. Paracetamol is commonly taken in overdose either deliberately or unintentionally. In high-income countries, paracetamol toxicity is a common cause of acute liver injury. There are various interventions to treat paracetamol poisoning, depending on the clinical status of the person. These interventions include inhibiting the absorption of paracetamol from the gastrointestinal tract (decontamination), removal of paracetamol from the vascular system, and antidotes to prevent the formation of, or to detoxify, metabolites.

OBJECTIVES

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

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register (January 2017), CENTRAL (2016, Issue 11), MEDLINE (1946 to January 2017), Embase (1974 to January 2017), and Science Citation Index Expanded (1900 to January 2017). We also searched the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov database (US National Institute of Health) for any ongoing or completed trials (January 2017). We examined the reference lists of relevant papers identified by the search and other published reviews.

SELECTION CRITERIA

Randomised clinical trials assessing benefits and harms of interventions in people who have ingested a paracetamol overdose. The interventions could have been gastric lavage, ipecacuanha, or activated charcoal, or various extracorporeal treatments, or antidotes. The interventions could have been compared with placebo, no intervention, or to each other in differing regimens.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from the included trials. We used fixed-effect and random-effects Peto odds ratios (OR) with 95% confidence intervals (CI) for analysis of the review outcomes. We used the Cochrane 'Risk of bias' tool to assess the risks of bias (i.e. systematic errors leading to overestimation of benefits and underestimation of harms). We used Trial Sequential Analysis to control risks of random errors (i.e. play of chance) and GRADE to assess the quality of the evidence and constructed 'Summary of findings' tables using GRADE software.

MAIN RESULTS

We identified 11 randomised clinical trials (of which one acetylcysteine trial was abandoned due to low numbers recruited), assessing several different interventions in 700 participants. The variety of interventions studied included decontamination, extracorporeal measures, and antidotes to detoxify paracetamol's toxic metabolite; which included methionine, cysteamine, dimercaprol, or acetylcysteine. There were no randomised clinical trials of agents that inhibit cytochrome P-450 to decrease the activation of the toxic metabolite N-acetyl-p-benzoquinone imine.Of the 11 trials, only two had two common outcomes, and hence, we could only meta-analyse two comparisons. Each of the remaining comparisons included outcome data from one trial only and hence their results are presented as described in the trials. All trial analyses lack power to access efficacy. Furthermore, all the trials were at high risk of bias. Accordingly, the quality of evidence was low or very low for all comparisons. Interventions that prevent absorption, such as gastric lavage, ipecacuanha, or activated charcoal were compared with placebo or no intervention and with each other in one four-armed randomised clinical trial involving 60 participants with an uncertain randomisation procedure and hence very low quality. The trial presented results on lowering plasma paracetamol levels. Activated charcoal seemed to reduce the absorption of paracetamol, but the clinical benefits were unclear. Activated charcoal seemed to have the best risk:benefit ratio among gastric lavage, ipecacuanha, or supportive treatment if given within four hours of ingestion. There seemed to be no difference between gastric lavage and ipecacuanha, but gastric lavage and ipecacuanha seemed more effective than no treatment (very low quality of evidence). Extracorporeal interventions included charcoal haemoperfusion compared with conventional treatment (supportive care including gastric lavage, intravenous fluids, and fresh frozen plasma) in one trial with 16 participants. The mean cumulative amount of paracetamol removed was 1.4 g. One participant from the haemoperfusion group who had ingested 135 g of paracetamol, died. There were no deaths in the conventional treatment group. Accordingly, we found no benefit of charcoal haemoperfusion (very low quality of evidence). Acetylcysteine appeared superior to placebo and had fewer adverse effects when compared with dimercaprol or cysteamine. Acetylcysteine superiority to methionine was unproven. One small trial (low quality evidence) found that acetylcysteine may reduce mortality in people with fulminant hepatic failure (Peto OR 0.29, 95% CI 0.09 to 0.94). The most recent randomised clinical trials studied different acetylcysteine regimens, with the primary outcome being adverse events. It was unclear which acetylcysteine treatment protocol offered the best efficacy, as most trials were underpowered to look at this outcome. One trial showed that a modified 12-hour acetylcysteine regimen with a two-hour acetylcysteine 100 mg/kg bodyweight loading dose was associated with significantly fewer adverse reactions compared with the traditional three-bag 20.25-hour regimen (low quality of evidence). All Trial Sequential Analyses showed lack of sufficient power. Children were not included in the majority of trials. Hence, the evidence pertains only to adults.

AUTHORS' CONCLUSIONS

These results highlight the paucity of randomised clinical trials comparing different interventions for paracetamol overdose and their routes of administration and the low or very low level quality of the evidence that is available. Evidence from a single trial found activated charcoal seemed the best choice to reduce absorption of paracetamol. Acetylcysteine should be given to people at risk of toxicity including people presenting with liver failure. Further randomised clinical trials with low risk of bias and adequate number of participants are required to determine which regimen results in the fewest adverse effects with the best efficacy. Current management of paracetamol poisoning worldwide involves the administration of intravenous or oral acetylcysteine which is based mainly on observational studies. Results from these observational studies indicate that treatment with acetylcysteine seems to result in a decrease in morbidity and mortality, However, further evidence from randomised clinical trials comparing different treatments are needed.

Bayesian Forecasting Tool to Predict the Need for Antidote in Acute Acetaminophen Overdose

STUDY OBJECTIVE

Acetaminophen (APAP) overdose is the leading cause of acute liver injury in the United States. Patients with elevated plasma acetaminophen concentrations (PACs) require hepatoprotective treatment with N-acetylcysteine (NAC). These patients have been primarily risk-stratified using the Rumack-Matthew nomogram. Previous studies of acute APAP overdoses found that the nomogram failed to accurately predict the need for the antidote. The objectives of this study were to develop a population pharmacokinetic (PK) model for APAP following acute overdose and evaluate the utility of population PK model-based Bayesian forecasting in NAC administration decisions.

DESIGN, PATIENTS AND MEASUREMENTS

Limited APAP concentrations from a retrospective cohort of acute overdosed subjects from the Maryland Poison Center were used to develop the population PK model and to investigate the effect of type of APAP products and other prognostic factors. The externally validated population PK model was used a prior for Bayesian forecasting to predict the individual PK profile when one or two observed PACs were available. The utility of Bayesian forecasted APAP concentration-time profiles inferred from one (first) or two (first and second) PAC observations were also tested in their ability to predict the observed NAC decisions.

MAIN RESULTS

A one-compartment model with first-order absorption and elimination adequately described the data with single activated charcoal and APAP products as significant covariates on absorption and bioavailability. The Bayesian forecasted individual concentration-time profiles had acceptable bias (6.2% and 9.8%) and accuracy (40.5% and 41.9%) when either one or two PACs were considered, respectively. The sensitivity and negative predictive value of the Bayesian forecasted NAC decisions using one PAC were 84% and 92.6%, respectively.

CONCLUSION

The population PK analysis provided a platform for acceptably predicting an individual's concentration-time profile following acute APAP overdose with at least one PAC, and the individual's covariate profile, and can potentially be used for making early NAC administration decisions.

Use and knowledge of single dose activated charcoal: A survey of Australian doctors

OBJECTIVE

The use of single dose activated charcoal (SDAC) as a means of gastric decontamination is declining. The present study examined the potential use of SDAC in common overdose scenarios by Australian emergency doctors, compared with clinical toxicologists and current guidelines.

METHODS

We conducted a cross-sectional survey of emergency doctors and toxicologists on the use of SDAC. The survey covered demographic data, education and previous use of SDAC and six clinical scenarios. The scenarios selected included agents not bound to SDAC, sustained-release preparations and ingestions at varying time points. Statistical calculations were performed using Fisher's exact test.

RESULTS

There were 397 emergency doctors and 20 toxicologists who responded to the survey. Seventy-one per cent (n = 280/397) of emergency doctors indicated they had received some education on decontamination. Eighty-three per cent (n = 331/397) had administered SDAC during their medical career, 29% (n = 117/397) within the past year. There was a significant difference in responses between emergency doctors and toxicologists in two scenarios; a toxic paracetamol ingestion presenting within 1 h (P = 0.009) and verapamil ingestion in a 3 year old boy (P = 0.001). Toxicologists were more likely to administer SDAC in these scenarios, 89% (n = 16/18) and 88% (n = 15/17), respectively, compared with 52% (n = 197/381) and 43% (n = 158/371) of emergency doctors.

CONCLUSIONS

Our study showed that there is a significant variation in the use of SDAC between toxicologists and emergency doctors in some scenarios. Clinical toxicologists are more likely to administer SDAC in certain overdose settings. It is essential to provide education on the benefits versus actual risks of SDAC in acute poisoning so that doctors will understand when to administer SDAC or seek further advice.

Current Controversies in Gastrointestinal Decontamination

Most poisonings reported to American poison control centers occur in the home. The most common route of exposure is ingestion, which is responsible for most fatalities. The goal of gastrointestinal decontamination is to prevent absorption of the toxin. Trends in treating poisoned patients have changed over the past few decades in light of a move toward practicing evidence-based medicine. Efficacy and clinical outcome have come into question and have led to position papers published recently regarding syrup of ipecac, gastric lavage, activated charcoal, and whole-bowel irrigation. These different methods of decontamination and the scientific data supporting each one will be reviewed, and the current controversies surrounding each will be discussed.

A retrospective review of the prehospital use of activated charcoal

OBJECTIVE

We studied the complications and timing implications of prehospital activated charcoal (PAC). Appropriateness of PAC administration was also evaluated.

METHODS

We retrospectively reviewed prehospital records over 32 months for overdose cases, where PAC was administered. Cases were assessed for amount and type of ingestant, clinical findings, timing of PAC, timing of transport and arrival into the emergency department (ED), and complications. Encounter duration in cases of PAC was compared with that, for all cases during the study period, where an overdose patient who did not receive activated charcoal was transported.

RESULTS

Two thousand eight hundred forty-five total cases were identified. In 441 cases, PAC was given; and complications could be assessed. Two hundred eighty-one of these had complete information regarding timing of ingestion, activated charcoal administration, and transport. The average time between overdose and PAC was 49.8 minutes (range, 7-199 minutes; median, 41.0 minutes; SD, 30.4 minutes). Complications included emesis (7%), declining mental status (4%), declining blood pressure (0.4%), and declining oxygen saturation (0.4%). Four hundred seventeen cases of PAC had documentation of timing of emergency medical service (EMS) arrival on scene and arrival at the ED. Average EMS encounter time was 29 minutes (range, 10-53 minutes; median, 27.9 minutes). Two thousand forty-four poisoning patients were transported who did not receive PAC. The average EMS encounter time for this group was 28.1 minutes (range, 4-82 minutes; median, 27.3 minutes), not significantly different (P =.114).

CONCLUSIONS

Prehospital activated charcoal did not appear to markedly delay transport or arrival of overdose patients into the ED and was generally safe.

Effect of activated charcoal on apixaban pharmacokinetics in healthy subjects

Background

Activated charcoal is commonly used to manage overdose or accidental ingestion of medicines. This study evaluated the effect of activated charcoal on apixaban exposure in human subjects.

Methods

This was an open-label, three-treatment, three-period, randomized, crossover study of single-dose apixaban (20 mg) administered alone and with activated charcoal given at 2 or 6 h post-dose to healthy subjects. Blood samples for assay of plasma apixaban concentration were collected up to 72 h post-dose. Pharmacokinetic parameters, including peak plasma concentration (C_max), time to C_max (T_max), area under the concentration–time curve from time 0 to infinity (AUC_INF), and terminal half-life (T_½), were derived from apixaban plasma concentration–time data. A general linear mixed-effect model analysis of C_max and AUC_INF was performed to estimate the effect of activated charcoal on apixaban exposure.

Results

A total of 18 subjects were treated and completed the study. AUC_INF for apixaban without activated charcoal decreased by 50 and 28 %, respectively, when charcoal was administered at 2 and 6 h post-dose. Apixaban C_max and T_max were similar across treatments. The mean T_½ for apixaban alone (13.4 h) decreased to ~5 h when activated charcoal was administered at 2 or 6 h post-dose. Overall, apixaban was well tolerated in this healthy population, and most adverse events were consistent with the known profile of activated charcoal.

Conclusion

Administration of activated charcoal up to 6 h after apixaban reduced apixaban exposure and facilitated the elimination of apixaban. These results suggest that activated charcoal may be useful in the management of apixaban overdose or accidental ingestion.

Amitriptyline, clomipramine, and doxepin adsorption onto sodium polystyrene sulfonate

Purpose of the study

Comparative in vitro studies were carried out to determine the adsorption characteristics of 3 drugs on activated charcoal (AC) and sodium polystyrene sulfonate (SPS). Activated charcoal (AC) has been long used as gastric decontamination agent for tricyclic antidepressants (TCA).

Methods

Solutions containing drugs (amitriptyline, clomipramine, or doxepin) and variable amount of AC or SPS were incubated for 30 minutes.

Results

At pH 1.2 the adsorbent: drug mass ratio varied from 2 : 1 to 40 : 1 for AC, and from 0.4 : 1 to 8 : 1 for SPS. UV–VIS spectrophotometer was used for the determination of free drug concentrations. The qmax of amitriptyline was 0.055 mg/mg AC and 0.574 mg/mg SPS, qmax of clomipramine was 0.053 mg/mg AC and 0.572 mg/mg SPS, and qmax of doxepin was 0.045 mg/mg AC and 0.556 mg/mg SPS. The results of adsorption experiments with SPS revealed higher values for the qmax parameters in comparison with AC.

Conclusion

In vitro gastric decontamination experiments for antidepressant amitriptyline, clomipramine, and doxepin showed that SPS has higher qmax values than the corresponding experiments with AC. Therefore, we suggest SPS is a better gastric decontaminating agent for the management of acute TCA intoxication.

Gastrointestinal decontamination in the acutely poisoned patient

Objective

To define the role of gastrointestinal (GI) decontamination of the poisoned patient.

Data Sources

A computer-based PubMed/MEDLINE search of the literature on GI decontamination in the poisoned patient with cross referencing of sources.

Study Selection and Data Extraction

Clinical, animal and in vitro studies were reviewed for clinical relevance to GI decontamination of the poisoned patient.

Data Synthesis

The literature suggests that previously, widely used, aggressive approaches including the use of ipecac syrup, gastric lavage, and cathartics are now rarely recommended. Whole bowel irrigation is still often recommended for slow-release drugs, metals, and patients who "pack" or "stuff" foreign bodies filled with drugs of abuse, but with little quality data to support it. Activated charcoal (AC), single or multiple doses, was also a previous mainstay of GI decontamination, but the utility of AC is now recognized to be limited and more time dependent than previously practiced. These recommendations have resulted in several treatment guidelines that are mostly based on retrospective analysis, animal studies or small case series, and rarely based on randomized clinical trials.

Conclusions

The current literature supports limited use of GI decontamination of the poisoned patient.

Activated charcoal: to give or not to give?

There has been much debate about the use of activated charcoal in patients who have taken overdoses and then present to Emergency Departments. There are clinical trials, research and position statements that have examined the effectiveness of activated charcoal in a number of overdoses of different medications, but there is still a debate surrounding the evidence based practice of administering activated charcoal in patients who have taken a drug overdose due to lack of evidence. This article will examine on the two main guidelines on activated charcoal, one produced by the National Institute for Clinical Excellence and the second produced by American Academy of Clinical Toxicology. It will discuss the methods of administration on activated charcoal, contraindications and the difficulties or challenges in adhering to these guidelines in the clinical setting.

Effect of delayed activated charcoal on acetaminophen concentration after simulated overdose of oxycodone and acetaminophen

OBJECTIVE

To determine the effect of activated charcoal (AC) on acetaminophen (APAP) absorption kinetics when administered at 1, 2, or 3 h after combined oral overdose with oxycodone.

METHODS

IRB-approved, prospective cross-over study of nine healthy human volunteers ingesting 5 g of APAP + 0.5 mg/kg of oxycodone on each of four study days. On the control day, subjects received no AC. On the remaining study days, subjects ingested 50 g of AC at 1, 2, or 3 h after drug ingestion. We measured serum APAP concentration hourly from 0 through 8 h and compared basic non-compartmental pharmacokinetic parameters.

RESULTS

Compared to the control, AC reduced area under the curve by 43% when given at 1 h (p < 0.0001), 22% when given at 2 h (p = 0.02), and 15% when given at 3 h (p = 0.26). AC at 1 h resulted in a 25% reduction in peak APAP concentration from 48.6 to 36.3 mcg/mL (p = 0.012) with no significant difference when given at 2 or 3 h. There was no significant difference in elimination half-life among the four study days.

CONCLUSION

The effect of AC rapidly declines between 1 and 3 h after combined oral overdose of APAP and oxycodone. AC is unlikely to be beneficial at or beyond 2 h after an overdose of acetaminophen and oxycodone.

Gastrointestinal decontamination of the poisoned patient

Gastrointestinal decontamination has been a historically accepted modality in the emergency management of oral intoxicants. Theoretically, gastric and whole-bowel emptying procedures hinder absorption, remove toxic substances, prevent clinical deterioration, and hasten recovery. This article presents a current overview of gastrointestinal decontamination. It challenges the accepted precepts of gut decontamination and assesses the utility of syrup of ipecac-induced emesis, orogastric lavage, single-dose-activated charcoal, cathartics, and whole-bowel irrigation.

Treatment in the pediatric emergency department is evidence based: a retrospective analysis

BACKGROUND

Our goal was to quantify the evidence that is available to the physicians of a pediatric emergency department (PED) in making treatment decisions. Further, we wished to ascertain what percentage of evidence for treatment provided in the PED comes from pediatric studies.

METHODS

We conducted a retrospective chart review of randomly selected patients seen in the PED between January 1 and December 31, 2002. The principal investigator identified a primary diagnosis and primary intervention for each chart. A thorough literature search was then undertaken with respect to the primary intervention. If a randomized control trial (RCT) or a systematic review was found, the intervention was classified as level I evidence. If no RCT was found, the intervention was assessed by an expert committee who determined its appropriateness based on face validity (RCTs were unanimously judged to be both unnecessary and, if a placebo would have been involved, unethical). These interventions were classified as level II evidence. Interventions that did not fall into either above category were classified as level III evidence.

RESULTS

Two hundred and sixty-two patient charts were reviewed. Of these, 35.9% did not receive a primary intervention. Of the 168 interventions assessed, 80.4% were evidence-based (level I), 7.1% had face validity (level II) and 12.5% had no supporting evidence (level III). Of the evidence-based interventions, 83.7% were supported by studies with mostly pediatric patients.

CONCLUSION

Our study demonstrates that a substantial proportion of PED treatment decisions are evidence-based, with most based on studies in pediatric patients. Also, a large number of patients seen in the PED receive no intervention.

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).

The Changing Indications of Gastrointestinal Decontamination in Poisonings

Gastrointestinal (GI) decontamination is commonly used in the treatment of the poisoned patient. Although the practice is widely accepted, the science behind the recommendations is limited. This article describes commonly used techniques for GI decontamination and critically reviews the studies evaluating these treatments.

Gastrointestinal decontamination

Overall, no conclusive data support the use of gastric decontamination in the routine management of the poisoned patient. Studies of asymptomatic patients suggest that no treatment is required, and, given the complications that have been reported, this may be a reasonable approach to' most patients. Even in symptomatic patients, the only demonstrable benefit was found in a post-hoc subgroup analysis and involved an outcome of questionable clinical importance. Given these data, it would be easy to conclude that GI decontamination has no role in the management of the poisoned patient. This conclusion is valid when considering poisoned patients as a group, but all poisoned patients are not the same. Patients with trivial ingestion do well without treatment, and their greatest risk is an iatrogenic complication. Even patients with more serious ingestions usually have good outcomes with supportive care alone. It is no longer sufficient to justify GL or forced administration of AC with the supposition that "the patient could have taken something bad." However,there are some overdoses where limiting the systemic absorption of the poison may limit the toxic effects and prevent serious toxicity. After careful consideration of the risks, GI decontamination should be targeted at patients who, in the opinion of the treating physician, have a potentially life-threatening exposure.

Drug Interactions with Paracetamol

Paracetamol (acetaminophen) is one of the most commonly used analgesic antipyretic drugs worldwide, and it is widely available by prescription and over the counter (OTC). Fortunately, few clinically significant drug interactions have been documented. There is probable potentiation of hepatotoxicity following an overdose from the paracetamol metabolite NAPQI by enzyme-inducing drugs. There is considerable controversy regarding the possible interaction with warfarin in its potential to increase its anticoagulant effects because of discrepancies between observational studies and those in healthy volunteers. Otherwise, no serious adverse drug interactions with therapeutic doses of paracetamol have been confirmed in humans. Because the absorption of paracetamol is so dependent on gastric emptying, other drugs that alter gastric emptying can change its pharmacokinetics; but this would not cause serious adverse effects. Although animal experiments have demonstrated that many compounds can modify paracetamol hepatotoxicity, these are unlikely to be important at therapeutic doses.

Comparison of Patient Questionnaires and Plasma Assays in Intentional Drug Overdoses

Our aim was to explore the agreement between clinically collected information on purported drug intake and plasma data in intentional drug overdose. We included all subjects with intentional drug overdose above 15 years of age consecutively admitted to the Emergency Department of the University Hospital during 4 months. Information about drugs used and sources of this information was collected and compared to presence of drug in plasma, concerning four drugs with high toxic potential (tricyclic antidepressants, meprobamate, paracetamol and ethanol). Sensitivity, specificity, predictive positive and negative values of all sources of information pooled were assessed for each drug. 413 intentional drug overdoses were included, 66% with more than one drug. According to clinical information, 8% took tricyclic antidepressants, 11% meprobamate, 9% paracetamol and 41% ethanol. Systematic plasma assays confirmed this in 59% of cases for tricyclic antidepressants, 76% for meprobamate and ethanol, and 77% for paracetamol. Plasma concentrations were considered toxic in 28% of cases for tricyclic antidepressants, 65% for meprobamate, 43% for ethanol and never for paracetamol. Tricyclic antidepressants and meprobamate were found unexpectedly in 3%, paracetamol in 7% and ethanol in 6%. Toxic concentrations were found only with meprobamate. The risk of erroneous, clinically collected information was greater by excess (25 to 40% false positives) than by lack (3 to 7% false negatives). Thus, the consequences of erroneous, clinically collected information were probably more excess cost for the institution than medical risk for the patients. However these results found at the population level may not be true at an individual level.

Of consents and CONSORTs: reporting ethics, law, and human rights in RCTs involving monitored overdose of healthy volunteers pre and post the "CONSORT" guidelines

Randomized controlled trials (RCTs) of therapeutic interventions in acute drug overdose present a significant challenge for ethical, legal, and human rights protections of research subjects, particularly when healthy volunteers are involved. The CONSORT statement on the uniform reporting of clinical trials was published in 1996 with the overall aim of improving the reporting of RCTs, both individually and to facilitate their inclusion into systematic reviews. In CONSORT, reporting of ethical, legal, and human rights protections, including prior evaluation of the study by an ethics committee and provision of informed consent, was largely an implicit requirement. Those drafting CONSORT may have assumed such protections and the rights of study subjects were secured by existing doctor-patient relationships. Alternatively, CONSORT may have been viewed as likely to indirectly enhance such protections, as a flow-on effect of improved RCT design and reporting. We wished to examine whether such assumptions were justified by examining the reporting of RCTs of simulated overdose in healthy volunteers. We reviewed all reported RCTs involving activated charcoal in healthy human volunteersfor three years before the CONSORT statement (1989, 1990, and 1991) and three years afterwards (1999, 2000, 2001). Presence of documentation of inclusion and exclusion criteria, stopping rules, protocol deviations, information sheets, consent documentation, ethical approvals, conflicts of interest, understanding, refusal, inducements and coercion were recorded. We found a very poor level of reporting of some key ethical, legal, and human rights protections for healthy volunteers in toxicological RCTs. Reporting did not improve with the publication of CONSORT even in relation to requirements specifically included in the guidelines.

Efficacy of superactivated charcoal administered late (3 hours) after acetaminophen overdose

The purpose of this study was to investigate the effect of superactivated charcoal (SAC) given late after a drug overdose. Acetaminophen was chosen as our overdose drug because it has relatively few side effects, serum levels are easily attainable and measurable, and it is generally a common drug overdose. Forty-six healthy adult volunteers participated in this randomized, controlled study. Acetaminophen was administered the morning after an overnight fast. Thirteen participants received 2000 mg acetaminophen and the remaining 33 received 3000 mg. After 3 hours, half of the participants (22 of 46) received 75 g of SAC (Requa, Greenwich, CT) orally as a slurry in 8 oz of apple juice. Serum acetaminophen levels were measured at 4 and 7 hours after the initial acetaminophen administration. There were significantly lower uncorrected and corrected acetaminophen levels in the SAC group compared with the control group at both 4 and 7 hours after ingesting acetaminophen. This randomized human experimental design trial demonstrates some detoxification benefit in administering superactivated charcoal 3 hours after an overdose.

Avaliação do emprego dos adsorventes: carvão ativo, chromosorb W e membrana C18 na preparação de amostras de ar para a determinação de d-aletrina em ambientes fechados

Os piretróides sintéticos são inseticidas amplamente utilizados para o controle de agentes patogênicos, desde a produção agrícola até a proteção da saúde humana, porém, apesar de suas inúmeras vantagens podem causar intoxicações em indivíduos potencialmente expostos a suas diversas apresentações. Amostras de ar foram coletadas pela geração da atmosfera padrão, onde a d-aletrina foi adsorvida em cartuchos contendo Carvão Ativo, Chromosorb W e/ou Membrana C18. As determinações das concentrações da d-aletrina foram efetuadas empregando um sistema de cromatografia gasosa. Os adsorventes Carvão ativo, Chromosorb W e Membrana C18 apresentaram adsorções de 100,8., 104,1 e 100,5%, com um desvio padrão relativo de 4,1, 7,5 e 7,9%, respectivamente. Coletou-se amostras de ar para a determinação da concentração da d-aletrina em diferentes em ambientes fechados, em diferentes dias da semana, obtendo-se níveis de concentração de d-aletrina de 3,4., 8,5 e 12,7 mig.m³, respectivamente.

The role of activated charcoal and gastric emptying in gastrointestinal decontamination: a state-of-the-art review

Gastrointestinal decontamination has been practiced for hundreds of years; however, only in the past few years have data emerged that demonstrate a clinical benefit in some patients. Because most potentially toxic ingestions involve agents that are not toxic in the quantity consumed, the exact circumstances in which decontamination is beneficial and which methods are most beneficial in those circumstances remain important topics of research. Maximum benefit from decontamination is expected in patients who present soon after the ingestion. Unfortunately, many overdose patients present at least 2 hours after taking a medication, when most of the toxin has been absorbed or has moved well into the intestine, beyond the expected reach of gastrointestinal decontamination. Decontamination probably does not contribute to the outcome of many such patients, especially those without symptoms. However, if absorption has been delayed or gastrointestinal motility has been slowed, activated charcoal may reduce the final amount absorbed. The use of activated charcoal in these cases may be beneficial and is associated with few complications. Therefore, administration of activated charcoal is recommended as soon as possible after emergency department presentation, unless the agent and quantity are known to be nontoxic, the agent is known not to adsorb to activated charcoal, or the delay has been so long that absorption is probably complete. The use of gastric emptying in addition to activated charcoal has generated intense debate. Several large comparative studies have failed to demonstrate a benefit of gastric emptying before activated charcoal. Because complications of such 2-step decontamination include a higher rate of intubation, aspiration, and ICU admission, gastric emptying in addition to activated charcoal cannot be considered the routine approach to patients. However, there are several infrequent circumstances in which the data are inadequate to accurately assess the potential benefit of gastric emptying in addition to activated charcoal: symptomatic patients presenting in the first hour after ingestion, symptomatic patients who have ingested agents that slow gastrointestinal motility, patients taking sustained release medications, and those taking massive or life-threatening amounts of medication. These circumstances represent only a small subset of ingestions. In the absence of convincing data about benefit or lack of benefit of gastric emptying for these patients, individual physicians must act on a personal valuation: Is it better to use a treatment that might have some benefit but definitely has some risk or not to use a treatment that has any risk unless there is proven benefit?

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.

Activated charcoal alone or after gastric lavage: a simulated large paracetamol intoxication

AIMS

Activated charcoal is now being recommended for patients who have ingested potentially toxic amounts of a poison, where the ingested substance adsorbs to charcoal. Combination therapy with gastric lavage and activated charcoal is widely used, although clinical studies to date have not provided evidence of additional efficacy compared with the use of activated charcoal alone. There are also doubts regarding the efficacy of activated charcoal, when administered more than 1 h after the overdose. The aim of this study was to examine if there was a difference in the effect of the two interventions 1 h post ingestion, and to determine if activated charcoal was effective in reducing the systemic absorption of a drug, when administered 2 h post ingestion.

METHODS

We performed a four-limbed randomized cross-over study in 12 volunteers, who 1 h after a standard meal ingested paracetamol 50 mg kg(-1) in 125 mg tablets to mimic real-life, where several factors, such as food, interfere with gastric emptying and thus treatment. The interventions were activated charcoal after 1 h, combination therapy of gastric lavage followed by activated charcoal after 1 h, or activated charcoal after 2 h. Serum paracetamol concentrations were determined by h.p.l.c. Percentage reductions in the area under the curve (AUC) were used to estimate the efficacy of each intervention (paired observations).

RESULTS

There was a significant (P<0.005) reduction in the paracetamol AUC with activated charcoal at 1 h (median reduction 66%, 95% confidence intervals 49, 76) compared with controls, and a significant (P<0.01) reduction for gastric lavage followed by activated charcoal at 1 h (median reduction 48.2%, 95% confidence interval 32.4, 63.7) compared with controls. There was no significant difference between the two interventions (95% confidence interval for the difference -3.8, 34.0). Furthermore, we found a significant (P<0.01) reduction in the paracetamol AUC when activated charcoal was administered 2 h after tablet ingestion when compared with controls (median 22.7%, 95% confidence intervals 13.6--34.4).

CONCLUSIONS

These results suggest that combination treatment may be no better than activated charcoal alone in patients presenting early after large overdoses. The effect of activated charcoal given 2 h post ingestion is substantially less than at 1 h, emphasizing the importance of early intervention.

How long after drug ingestion is activated charcoal still effective?

OBJECTIVE

The recent American Academy of Clinical Toxicology/European Association of Poisons Centres and Clinical Toxicologists position statement on activated charcoal stated "there are insufficient data to support or exclude its use after 1 hour of ingestion.'' The purpose of this study was to determine the effectiveness of activated charcoal administered 1, 2, and 3 hours after drug ingestion.

METHODS

This was a human volunteer, randomized crossover study. Ten volunteers ingested 4 g of acetaminophen on four occasions at least 1 week apart. One ingestion served as a control and the other three as experimental ingestions with charcoal being administered at 1, 2, and 3 hours after acetaminophen dosing. Eight blood specimens were obtained over the initial 8 hours for serum acetaminophen concentrations that were used for calculation of routine pharmacokinetic parameters. Repeated measures of ANOVA and Tukey's HSD test were used for statistical analysis.

RESULTS

Pharmacokinetic parameters for acetaminophen in our volunteers were consistent with literature values. The mean area under the curve (AUC+/-SD) for the control and the 1-, 2-, and 3-hour groups were 221 +/- 54, 154 +/- 71, 206 +/- 67 and 204 +/- 58 mg/L/h, respectively. The 1-hour group was the only one differing from control (p < 0.01). The decrease of bioavailability at 1 hour was 30.3%, which is similar to previous studies.

CONCLUSION

Our data do not support the administration of activated charcoal as a gastrointestinal decontamination strategy beyond 1 hour after drug overdose.

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.

The Impact of Carbon Surface Composition on the Diffusion and Adsorption of Paracetamol at Different Temperatures and at Neutral pH

Commercial activated carbon D43/1 (Carbo-Tech, Essen, Germany) was deashed and modified chemically to increase surface acidity and basicity, as well as to introduce metal cations onto the surface and yet conserve the porosity. The five carbons obtained were applied as adsorbents. Based on the results of batch-reactor test kinetic measurements of the adsorption of 4-hydroxyacetanilide (paracetamol) from aqueous solution at the neutral pH and at three temperatures (300, 310, and 320 K), the values of the effective diffusion coefficient (D(e)) were calculated. It is shown that D(e) increases (up to the relative adsorption equal to approximately 0.6) with rise in the magnitude of the enthalpy of immersion of carbons in water. Based on the obtained results as well as those published previously, the role of surface composition in the mechanism of paracetamol adsorption and in the kinetics of this process is discussed. Copyright 2000 Academic Press.