Acute ethanol coingestion confers a lower risk of hepatotoxicity after deliberate acetaminophen overdose

Acetaminophen induced hepatotoxicity: An overview of the promising protective effects of natural products and herbal formulations

BACKGROUND

The liver plays an important role in regulating the metabolic processes and is the most frequently targeted organ by toxic chemicals. Acetaminophen (APAP) is a well-known anti-allergic, anti-pyretic, non-steroidal anti-inflammatory drug (NSAID), which upon overdose leads to hepatotoxicity, the major adverse event of this over-the-counter drug.

PURPOSE

APAP overdose induced acute liver injury is the second most common cause that often requires liver transplantation worldwide, for which N-acetyl cysteine is the only synthetic drug clinically approved as an antidote. So, it was felt that there is a need for the novel therapeutic approach for the treatment of liver diseases with less adverse effects. This review provides detailed analysis of the different plant extracts; phytochemicals and herbal formulations for the amelioration of APAP-induced liver injury.

METHOD

The data was collected using different online resources including PubMed, ScienceDirect, Google Scholar, Springer, and Web of Science using keywords given below.

RESULTS

Over the past decades various reports have revealed that plant-based approaches may be a better treatment choice for the APAP-induced hepatotoxicity in pre-clinical experimental conditions. Moreover, herbal compounds provide several advantages over the synthetic drugs with fewer side effects, easy availability and less cost for the treatment of life-threatening diseases.

CONCLUSION

The current review summarizes the hepatoprotective effects and therapeutic mechanisms of various plant extracts, active phytoconstituents and herbal formulations with potential application against APAP induced hepatotoxicity as the numbers of hepatoprotective natural products are more without clinical relativity. Further, pre-clinical pharmacological research will contribute to the designing of natural products as medicines with encouraging prospects for clinical application.

Paracetamol (acetaminophen) overdose and hepatotoxicity: mechanism, treatment, prevention measures, and estimates of burden of disease

INTRODUCTION

Paracetamol is one of the most used medicines worldwide and is the most common important poisoning in high-income countries. In overdose, paracetamol causes dose-dependent hepatotoxicity. Acetylcysteine is an effective antidote, however despite its use hepatotoxicity and many deaths still occur.

AREAS COVERED

This review summarizes paracetamol overdose and toxicity (including mechanisms, risk factors, risk assessment, and treatment). In addition, we summarize the epidemiology of paracetamol overdose worldwide. A literature search on PubMed for poisoning epidemiology and mortality from 1 January 2017 to 26 October 2022 was performed to estimate rates of paracetamol overdose, liver injury, and deaths worldwide.

EXPERT OPINION

Paracetamol is widely available and yet is substantially more toxic than other analgesics available without prescription. Where data were available, we estimate that paracetamol is involved in 6% of poisonings, 56% of severe acute liver injury and acute liver failure, and 7% of drug-induced liver injury. These estimates are limited by lack of available data from many countries, particularly in Asia, South America, and Africa. Harm reduction from paracetamol is possible through better identification of high-risk overdoses, and better treatment regimens. Large overdoses and those involving modified-release paracetamol are high-risk and can be targeted through legislative change.

Molecular pathogenesis of acetaminophen-induced liver injury and its treatment options

Acetaminophen, also known as N-acetyl-p-aminophenol (APAP), is commonly used as an antipyretic and analgesic agent. APAP overdose can induce hepatic toxicity, known as acetaminophen-induced liver injury (AILI). However, therapeutic doses of APAP can also induce AILI in patients with excessive alcohol intake or who are fasting. Hence, there is a need to understand the potential pathological mechanisms underlying AILI. In this review, we summarize three main mechanisms involved in the pathogenesis of AILI: hepatocyte necrosis, sterile inflammation, and hepatocyte regeneration. The relevant factors are elucidated and discussed. For instance, N-acetyl-p-benzoquinone imine (NAPQI) protein adducts trigger mitochondrial oxidative/nitrosative stress during hepatocyte necrosis, danger-associated molecular patterns (DAMPs) are released to elicit sterile inflammation, and certain growth factors contribute to liver regeneration. Finally, we describe the current potential treatment options for AILI patients and promising novel strategies available to researchers and pharmacists. This review provides a clearer understanding of AILI-related mechanisms to guide drug screening and selection for the clinical treatment of AILI patients in the future.

Toxicological Analysis of Hepatocytes Using FLIM Technique: In Vitro versus Ex Vivo Models

The search for new criteria indicating acute or chronic pathological processes resulting from exposure to toxic agents, testing of drugs for potential hepatotoxicity, and fundamental study of the mechanisms of hepatotoxicity at a molecular level still represents a challenging issue that requires the selection of adequate research models and tools. Microfluidic chips (MFCs) offer a promising in vitro model for express analysis and are easy to implement. However, to obtain comprehensive information, more complex models are needed. A fundamentally new label-free approach for studying liver pathology is fluorescence-lifetime imaging microscopy (FLIM). We obtained FLIM data on both the free and bound forms of NAD(P)H, which is associated with different metabolic pathways. In clinical cases, liver pathology resulting from overdoses is most often as a result of acetaminophen (APAP) or alcohol (ethanol). Therefore, we have studied and compared the metabolic state of hepatocytes in various experimental models of APAP and ethanol hepatotoxicity. We have determined the potential diagnostic criteria including the pathologically altered metabolism of the hepatocytes in the early stages of toxic damage, including pronounced changes in the contribution from the bound form of NAD(P)H. In contrast to the MFCs, the changes in the metabolic state of hepatocytes in the ex vivo models are, to a greater extent, associated with compensatory processes. Thus, MFCs in combination with FLIM can be applied as an effective tool set for the express modeling and diagnosis of hepatotoxicity in clinics.

The Timing and Effects of Low-Dose Ethanol Treatment on Acetaminophen-Induced Liver Injury

Acetaminophen (APAP) overdose is the major cause of drug-induced liver injury and acute liver failure. Approximately 10% of APAP is metabolized by cytochrome P450 (CYP2E1) into toxic N-acetyl-p-benzoquinone imine (NAPQI). CYP2E1 also contributes to ethanol metabolism, especially during conditions of high blood ethanol concentration. Acute and chronic ethanol consumption appears to have opposite effects on APAP-induced liver injury. We determined the effects of different doses, pre- and post-treatment, and various schedules of ethanol exposure in APAP-induced liver injury. Treatment with ethanol (0.5 g/kg) after 1 h of APAP (300 mg/kg) administration decreased serum ALT levels, histopathological features, and inflammatory cell infiltration. Moreover, ethanol treatment 1 h after APAP treatment reduced APAP-induced liver injury compared with later administration. Interestingly, ethanol pretreatment did not provide any protective effect. Furthermore, ethanol treatment was associated with a significant decrease in ERK and AKT phosphorylation during the acute injury phase. Ethanol exposure also increased CYP2E1 expression and decreased PCNA expression during the liver regeneration phase.

Fructose Protects Against Acetaminophen-Induced Hepatotoxicity Mainly by Activating the Carbohydrate-Response Element-Binding Protein α-Fibroblast Growth Factor 21 Axis in Mice

Acetaminophen (N-acetyl-para-aminophenol [APAP]) overdose is the most common cause of drug-induced liver injury in the Western world and has limited therapeutic options. As an important dietary component intake, fructose is mainly metabolized in liver, but its impact on APAP-induced liver injury is not well established. We aimed to examine whether fructose supplementation could protect against APAP-induced hepatotoxicity and to determine potential fructose-sensitive intracellular mediators. We found that both high-fructose diet feeding before APAP injection and fructose gavage after APAP injection reduced APAP-induced liver injury with a concomitant induction of the hepatic carbohydrate-response element-binding protein α (ChREBPα)-fibroblast growth factor 21 (FGF21) pathway. In contrast, Chrebpα liver-specific-knockout (Chrebpα-LKO) mice failed to respond to fructose following APAP overdose, suggesting that ChREBPα is the essential intracellular mediator of fructose-induced hepatoprotective action. Primary mouse hepatocytes with deletion of Fgf21 also failed to show fructose protection against APAP hepatotoxicity. Furthermore, overexpression of FGF21 in the liver was sufficient to reverse liver toxicity in APAP-injected Chrebpα-LKO mice. Conclusion: Fructose protects against APAP-induced hepatotoxicity likely through its ability to activate the hepatocyte ChREBPα-FGF21 axis.

Concurrent administration of acetaminophen and ethanol: impact on mouse liver and testis

OBJECTIVES

Acetaminophen (paracetamol) and alcohol are widely consumed as analgesic/antipyretic and recreational agent, respectively. High doses of both agents induce liver and male reproductive toxicities. This study investigated the toxicological outcome of concurrent administration of paracetamol and ethanol in the liver and testis in mice.

METHODS

Animals were gavaged paracetamol (250 mg/kg), ethanol (3 g/kg) or paracetamol + ethanol for 2 d. Some groups were sacrificed 12 h after the last dose, while others were sacrificed 21 d posttreatment for reversibility study. Control group received carboxymethylcellulose sodium (0.2%). Serum levels of liver biochemical indices and epididymal sperm were analysed. Histopathological analysis of the liver and testis were also performed.

RESULTS

Alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin in serum were elevated (p<0.001); whereas albumin and total protein were reduced (p<0.001) in paracetamol or ethanol groups compared to control. In the combination group, only mild elevation of ALT (p<0.05) was observed. Additionally, hepatocyte necrosis occurred in the livers of paracetamol and ethanol groups, while only mild inflammatory changes were seen in the combination group. All liver indices were normal in reversibility study animals. Furthermore, sperm count, motility, viability and morphology did not change in all treated animals, except that sperm count was decreased (p<0.05) in paracetamol group. Testis histology of all animal groups were normal.

CONCLUSIONS

The results demonstrated that simultaneous treatment with acute paracetamol and ethanol doses will possibly minimize hepatotoxicity and reduction of epididymal sperm reserve by the individual agents, and the toxicities are reversible.

A clinician's guide to self-poisoning with paracetamol in youth: The what, when and why?

AIM

Deliberate self-poisoning or overdose is a common presentation to the paediatric emergency departments (ED) due to a lack of emergency access to child and adolescent mental health services. We overview medical and psychiatric assessment of overdoses in youth with the most commonly implicated drug, paracetamol, as a case study.

METHODS

A what, when and why framework is adopted to guide clinicians on what information should be ascertained, when overdose treatment should be initiated and how to explore why the overdose occurred.

RESULTS

Presentations are often asymptomatic while gastrointestinal symptoms offer an alarm signal for severe hepatotoxicity. A worst-case exposure amount and time elapsed since ingestion should be calculated to determine whether N-acetylcysteine treatment is indicated. Establishing reasons why the young person took the overdose, along with assessing the degree of remorse or regret, is crucial for discharge planning.

CONCLUSION

Given the importance of timely assessment and treatment, paediatric emergency staff need to be familiar with the protocol for care. Attention needs to be focused on both the medical and psychological risk, and staff need to consider the reasons behind the overdose and following a biopsychosocial assessment, ensure that the young person and family are adequately signposted for future mental health care if needed.

Methanol, Paracetamol Toxicities and Acute Blindness

Methanol toxicity remains a common problem in developing countries including Saudi Arabia. However, it is much less available than other toxins; thus, clinical suspicion and correlation play pivotal roles in diagnosis. On the other hand, paracetamol is widely available and overdose/toxicity is highly suspected especially in young females. Diagnosis of methanol toxicity can be difficult in cases where history is not readily available and it requires a high degree of suspicion, especially when ingestion of another substance is revealed first as should not preclude the possibility of co-ingestion. We report a case of a medically free 26 year old woman who was brought to the Emergency Department (ED) of our hospital with a history of ingestion of a massive amount of paracetamol tablets and a concurrent abdominal pain with vomiting. After arrival, she became unresponsive with Glasgow Coma score (GCS) of 8/15 and was mechanically ventilated. Initial laboratory investigations identify the paracetamol level of 1200 ug/ml and a significantly high anion gap metabolic acidosis. Owing to the suspicious circumstances and the depth of acidosis, a co-ingestion of methanol and ethylene glycol was suspected. Upon further evaluation, osmolal gap was found to be significantly high as well. Since neither volatile compound screening nor Fomepizole were available in our hospital, an urgent N-acetylcysteine and sodium bicarbonate (NaHCO₃) were started alongside hemodialysis. Subsequent brain computed tomography (CT) and magnetic reasoning imaging (MRI) revealed changes in putamen and basal ganglia most consistent with methanol toxicity. She was successively extubated on day four of hospitalization with residual visual deficits that had resolved eventually after several follow-ups.

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.

Acetaminophen (APAP or N-Acetyl-p-Aminophenol) and Acute Liver Failure

Acetaminophen (APAP) is the leading cause of acute liver failure (ALF), although the worldwide frequency is variable. APAP hepatotoxicity develops either following intentional overdose or unintentional ingestion (therapeutic misadventure) in the background of several factors, such as concomitant use of alcohol and certain medications that facilitate the formation of reactive and toxic metabolites. Spontaneous survival is more common in APAP-induced ALF compared with non-APAP etiologies. N-acetylcysteine is recommended for all patients with APAP-induced ALF and it reduces mortality. Liver transplantation should be offered early to those who are unlikely to survive based on described prognostic criteria.

Are some people at increased risk of paracetamol-induced liver injury? A critical review of the literature

Purpose

Paracetamol is one of the world’s most commonly used drugs. In overdose, it is well established to be hepatotoxic. The aim of this review was to identify factors that have been, or actually are, associated with the development of liver injury after paracetamol exposure in humans.

Method

Google Scholar and PubMed were searched on various dates between December 2016 and March 2017. Papers identified had their references analysed for further studies that might be relevant.

Results

At the time of writing, there was little good quality clinical evidence—from studies of paracetamol overdose or therapeutic use—to suggest that any groups of people are relatively protected from, or are at greater risk of, liver injury. The factors that were historically used to indicate higher risk in the UK have no good quality clinical evidence to support their re-introduction into clinical practice. The safe (and still effective) oral dose of paracetamol in patients weighing less than 50 kg has not been established.

Conclusion

There is no patient group that is unequivocally at elevated risk of paracetamol-induced liver toxicity. We propose two clinical scenarios that warrant further research. Firstly, there is a need to establish whether the dose of paracetamol should be reduced in patients with low body weight. Secondly, if or when genomic information regarding individual patients becomes readily available to inform prescribing, we propose the contribution of the genome to paracetamol toxicity should be re-investigated with robustly designed studies. Such studies could enhance the safe use of one of the most frequently taken drugs.

Electronic supplementary material

The online version of this article (10.1007/s00228-017-2356-6) contains supplementary material, which is available to authorized users.

The 100 most influential publications in paracetamol poisoning treatment: a bibliometric analysis of human studies

BACKGROUND

Analysis of the most influential publications within paracetamol poisoning treatment can be helpful in recognizing main and novel treatment issues within the field of toxicology. The current study was performed to recognize and describe the most highly cited articles related to paracetamol poisoning treatment.

METHODS

The 100 most highly cited articles in paracetamol poisoning treatment were identified from the Scopus database in November 2015. All eligible articles were read for basic information, including total number of citations, average citations per year, authors' names, journal name, impact factors, document types and countries of authors of publications.

RESULTS

The median number of citations was 75 (interquartile range 56-137). These publications were published between 1974 and 2013. The average number of years since publication was 17.6 years, and 45 of the publications were from the 2000s. A significant, modest positive correlation was found between years since publication and the number of citations among the top 100 cited articles (r = 0.316; p = 0.001). A total of 55 journals published these 100 most cited articles. Nine documents were published in Clinical Toxicology, whereas eight documents were published in Annals of Emergency Medicine. Citations per year since publication for the top 100 most-cited articles ranged from 1.5 to 42.6 and had a mean of 8.5 citations per year and a median of 5.9 with an interquartile range of 3.75-10.35. In relation to the origin of the research publications, they were from 8 countries. The USA had the largest number of articles, 47, followed by the UK and Australia with 38 and nine articles respectively.

CONCLUSIONS

This study is the first bibliometric assessment of the top 100 cited articles in toxicology literature. Interest in paracetamol poisoning as a serious clinical problem continues to grow. Research published in high-impact journals and from high income countries is most likely to be cited in published paracetamol research.

Acetaminophen-Induced Hepatotoxicity: a Comprehensive Update

Hepatic injury and subsequent hepatic failure due to both intentional and non-intentional overdose of acetaminophen (APAP) has affected patients for decades, and involves the cornerstone metabolic pathways which take place in the microsomes within hepatocytes. APAP hepatotoxicity remains a global issue; in the United States, in particular, it accounts for more than 50% of overdose-related acute liver failure and approximately 20% of the liver transplant cases. The pathophysiology, disease course and management of acute liver failure secondary to APAP toxicity remain to be precisely elucidated, and adverse patient outcomes with increased morbidity and mortality continue to occur. Although APAP hepatotoxicity follows a predictable timeline of hepatic failure, its clinical presentation might vary. N-acetylcysteine (NAC) therapy is considered as the mainstay therapy, but liver transplantation might represent a life-saving procedure for selected patients. Future research focus in this field may benefit from shifting towards obtaining antidotal knowledge at the molecular level, with focus on the underlying molecular signaling pathways.

Can paracetamol (acetaminophen) be administered to patients with liver impairment?

Although 60 years have passed since it became widely available on the therapeutic market, paracetamol dosage in patients with liver disease remains a controversial subject. Fulminant hepatic failure has been a well documented consequence of paracetamol overdose since its introduction, while short and long term use have both been associated with elevation of liver transaminases, a surrogate marker for acute liver injury. From these reports it has been assumed that paracetamol use should be restricted or the dosage reduced in patients with chronic liver disease. We review the factors that have been purported to increase risk of hepatocellular injury from paracetamol and the pharmacokinetic alterations in different pathologies of chronic liver disease which may affect this risk. We postulate that inadvertent under-dosing may result in concentrations too low to enable efficacy. Specific research to improve the evidence base for prescribing paracetamol in patients with different aetiologies of chronic liver disease is needed.

Ethanol consumption produces a small increase in circulating miR-122 in healthy individuals

INTRODUCTION

MicroRNA 122 (miR-122) is a new circulating biomarker for liver injury, which increases earlier than conventional markers in patients with acetaminophen hepatotoxicity. However, as co-ingestion of ethanol is common with drug overdose, a confounding effect of acute ethanol consumption on serum miR-122 must be examined.

METHODS

Blood was collected from healthy volunteers before and after recreational consumption of ethanol. Routine biochemistry and haematology measurements were performed, and serum miR-122 was measured by qPCR. The primary outcome was the difference in serum miR-122 with ethanol consumption.

RESULTS

We recruited 18 participants (72% male). Their mean serum ethanol concentration was 113 mg/dl (95% confidence interval [CI] 91-135 mg/dl) after consuming ethanol. Serum miR-122 increased from a mean of 71.3 million (95% CI 29.3-113.2 million) to 139.1 million (95% CI 62.6-215.7 million) copies/ml (2.2-fold increase). There was no significant difference in serum alanine aminotransferase activity before and after ethanol consumption.

CONCLUSION

miR-122 increased with moderate ethanol consumption, but the fold change was modest. As increases with acetaminophen toxicity are 100- to 10 000-fold, moderate ethanol intoxication is unlikely to confound the use of this biomarker of hepatotoxicity.

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.

Impact of amending the acetylcysteine marketing authorisation on treatment of paracetamol overdose

In September 2012, the Medicines and Healthcare products Regulatory Agency (MHRA) substantially amended the Marketing Authorisation for acetylcysteine following an extensive review. The present study examined the impact of this license change on patterns of acetylcysteine use in patients presenting to hospital after paracetamol (acetaminophen) overdose. Between September 2011 and April 2013, 785 consecutive patients presented to York Hospital due to paracetamol overdose, and a before-after analysis was used to compare outcomes. There were 483 patients before and 302 patients after the license amendment, and age, gender, acute or staggered overdose pattern, and dose were similar in both groups. In the patients with paracetamol concentrations between the "100-line" and "200-line," a significantly higher proportion received acetylcysteine treatment (51% before versus 98% after, P = 0.0029), as expected. A modest increase was also observed in relation to late or staggered overdose or cases where the time of ingestion was uncertain (53% versus 74%, P = 0.0430). The median duration of hospital stay increased across the entire study population, from 15 to 24 hours (P = 0.0159) due to the increased proportion of patients requiring acetylcysteine treatment. The findings indicate that the MHRA amendment is a financially costly intervention, and further studies are needed to examine clinical outcomes so that its cost effectiveness might be addressed.

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.

Metabolism and disposition of acetaminophen: recent advances in relation to hepatotoxicity and diagnosis

Acetaminophen (APAP) is one of the most widely used drugs. Though safe at therapeutic doses, overdose causes mitochondrial dysfunction and centrilobular necrosis in the liver. The first studies of APAP metabolism and activation were published more than 40 years ago. Most of the drug is eliminated by glucuronidation and sulfation. These reactions are catalyzed by UDP-glucuronosyltransferases (UGT1A1 and 1A6) and sulfotransferases (SULT1A1, 1A3/4, and 1E1), respectively. However, some is converted by CYP2E1 and other cytochrome P450 enzymes to a reactive intermediate that can bind to sulfhydryl groups. The metabolite can deplete liver glutathione (GSH) and modify cellular proteins. GSH binding occurs spontaneously, but may also involve GSH-S-transferases. Protein binding leads to oxidative stress and mitochondrial damage. The glucuronide, sulfate, and GSH conjugates are excreted by transporters in the canalicular (Mrp2 and Bcrp) and basolateral (Mrp3 and Mrp4) hepatocyte membranes. Conditions that interfere with metabolism and metabolic activation can alter the hepatotoxicity of the drug. Recent data providing novel insights into these processes, particularly in humans, are reviewed in the context of earlier work, and the effects of altered metabolism and reactive metabolite formation are discussed. Recent advances in the diagnostic use of serum adducts are covered.

Novel acetylcysteine regimens for treatment of paracetamol overdose

Paracetamol (acetaminophen) overdose remains the leading cause of death or transplantation due to acute liver failure in many parts of the world. Acetylcysteine has long been recognized as an effective antidote, via oral or intravenous administration, minimizing the risk and severity of acute liver injury if administered sufficiently early after a paracetamol overdose. Despite this, its mechanisms of action remain obscure, and there is uncertainty regarding the optimal dose and duration of treatment. The intravenous infusion protocol was originally developed as a three-step loading regimen; it causes very high early peak plasma concentrations of acetylcysteine whereas the later maintenance infusion is associated with much lower concentrations. This pharmacokinetic profile is associated with two particular concerns: a high rate of occurrence of adverse effects that occur after the initial loading infusion, and the possibility that the maintenance phase of treatment might deliver too low a dose of acetylcysteine for optimum protection against liver injury. Recently described novel administration regimens offer different rates of intravenous acetylcysteine administration in both the loading and maintenance phases. These alternative regimens appear to be well tolerated in small patient groups, but too few clinical data are available to evaluate their comparative efficacy in preventing paracetamol-induced liver injury.

Effect of therapeutic doses of acetaminophen (up to 4 g/day) on serum alanine aminotransferase levels in subjects consuming ethanol: systematic review and meta-analysis of randomized controlled trials

STUDY OBJECTIVE

To quantify the effect of therapeutic doses of acetaminophen on serum alanine aminotransferase (ALT) levels in subjects who consumed ethanol.

DESIGN

Systematic review of six randomized placebo-controlled trials, of which five were included in a meta-analysis.

SUBJECTS

Subjects included in the meta-analysis were those who consumed ethanol and received acetaminophen in doses up to 4 g/day (551 subjects) or placebo (350 subjects).

MEASUREMENTS AND MAIN RESULTS

A comprehensive literature search of the MEDLINE, EMBASE, and International Pharmaceutical Abstracts databases and the Cochrane Central Register of Controlled Trials was performed to identify randomized, placebo-controlled trials that enrolled subjects who consumed ethanol, received acetaminophen in therapeutic doses up to 4 g/day, and had serum ALT level measurements. A total of 184 articles were identified; six articles met all criteria. Five of the six articles reported ALT levels on study day 4 for both groups of subjects who received acetaminophen or placebo. Thus, for the meta-analysis, we used the primary outcome of mean change in serum ALT level from baseline to day 4 in the acetaminophen groups compared with the placebo groups. We found that the difference in mean change from baseline ALT levels between the acetaminophen and placebo groups on day 4 was 0.0 U/L (95% confidence interval -0.2-0.1 U/L). There were no reports of liver dysfunction, liver failure, or death in any of the trials.

CONCLUSION

In randomized, placebo-controlled trials of subjects who consumed ethanol, no elevation of ALT level on study day 4 was noted when subjects ingested up to 4 g/day of acetaminophen.

Comparative drug dose and drug combinations in patients that present to hospital due to self-poisoning

Self-poisoning is a common reason for acute presentation to hospital. Commonly involved drugs have been reported, but few data exist concerning the different combinations of agents or comparative doses ingested. The present study sought to better characterise the typical patterns of drug overdose that may present via the emergency department. Consecutive adults ≥16 years of age that presented to York Hospital owing to self-poisoning were studied for 2010-2011 inclusive. The primary outcome measure was reported dose, expressed as a multiple of the defined daily dose (DDD) to allow comparison between different agents. There were 1024 patients, including 622 women (60.7%), and median age was 32 years (range, 16 to 92 years). Overdose in men was associated with a higher overall quantity of drugs: arithmetic mean of 20 DDD multiples (95% CI, 15-26) versus 13 (11-15), p = 0.001. Overdose involved a single agent only in 538 patients (52.5%). The mean paracetamol dose was 4.0 (95% CI, 3.7-4.3) DDD multiples; the doses of antidepressants (19.4, 17.0-21.7, p < 0.0001) and benzodiazepines (18.0, 12.8-23.2, p < 0.0001) were comparatively higher. The types of agents involved in self-poisoning and common combinations of agents are characterised. Psychotropic medications were ingested in comparatively larger quantities than analgesic agents and had worse clinical outcome. Further work is required to understand the factors that determine the quantity of drug ingested in patients at risk of drug overdose so as to minimise the risk of significant toxicity.

Staggered overdose pattern and delay to hospital presentation are associated with adverse outcomes following paracetamol-induced hepatotoxicity

AIMS

Paracetamol (acetaminophen) poisoning remains the major cause of severe acute hepatotoxicity in the UK. In this large single centre cohort study we examined the clinical impact of staggered overdoses and delayed presentation following paracetamol overdose.

RESULTS

Between 1992 and 2008, 663 patients were admitted with paracetamol-induced severe liver injury, of whom 161 (24.3%) had taken a staggered overdose. Staggered overdose patients were significantly older and more likely to abuse alcohol than single time point overdose patients. Relief of pain (58.2%) was the commonest rationale for repeated supratherapeutic ingestion. Despite lower total ingested paracetamol doses and lower admission serum alanine aminotransferase concentrations, staggered overdose patients were more likely to be encephalopathic on admission, require renal replacement therapy or mechanical ventilation and had higher mortality rates compared with single time point overdoses (37.3% vs. 27.8%, P= 0.025), although this overdose pattern did not independently predict death. The King's College poor prognostic criteria had reduced sensitivity (77.6, 95% CI 70.8, 81.5) for this pattern of overdose. Of the 396/450 (88.0%) single time point overdoses in whom accurate timings could be obtained, 178 (44.9%) presented to medical services >24 h following overdose. Delayed presentation beyond 24 h post overdose was independently associated with death/liver transplantation (OR 2.25, 95% CI 1.23, 4.12, P= 0.009).

CONCLUSIONS

Both delayed presentation and staggered overdose pattern are associated with adverse outcomes following paracetamol overdose. These patients are at increased risk of developing multi-organ failure and should be considered for early transfer to specialist liver centres.

The therapeutic applications of and risks associated with acetaminophen use: a review and update

BACKGROUND

In response to the April 2010 U.S. Food and Drug Administration's (FDA's) revision of warning labeling for over-the-counter (OTC) acetaminophen, or N-acetyl-p-aminophenol (APAP), products, the authors reviewed APAP's potential for liver toxicity.

TYPES OF STUDIES REVIEWED

The authors reviewed the literature in which investigators examined data related to the epidemiology of APAP-related liver toxicity, studies in which the investigators evaluated the risk factors for its occurrence and case reports. They included articles that were used by the FDA as the basis for establishing the new labeling requirements.

RESULTS

Findings from the literature in which investigators have examined the relationship between APAP and liver toxicity indicate several key risk factors. Foremost are the extensive use of one or more APAP-containing compounds (particularly combinations with opioid agents) and the small margin of safety between the therapeutic and toxic doses. Both of these factors lead to unintentional or intentional drug overdose. Concurrent use of alcohol may contribute to hepatotoxicity, but it may be related to behavior rather than biochemical mechanisms involved in liver damage.

CONCLUSIONS

The widespread use of APAP has contributed to a substantial increase in the number of cases of acute liver toxicity in the United States. Since APAP is a component of many prescription and OTC medications, unintentional overdose can occur.

CLINICAL IMPLICATIONS

APAP has numerous applications in dentistry, but if it is used conjointly for other conditions, the risk of the patient's experiencing an overdose increases. In the context of recent FDA concerns about the increased incidence of APAP-related liver toxicity, the authors provide recommendations for safe prescribing practices for APAP. Practitioners should caution patients to follow recommended dosage instructions and avoid taking multiple APAP-containing products.

Drug-induced liver injury: what was new in 2008?

BACKGROUND

Given the number of publications appearing annually regarding drug-induced liver injury (DILI), there remains a need to concisely summarize each year's new crop of case series and reports as well as the advances in mechanisms of liver injury and in the field of pharmacogenomics relating to DILI.

OBJECTIVE

To present an up-to-date review of the past year's most important clinical studies and reports of DILI, placing them into context of previous publications.

METHODS

A Medline search was conducted of all manuscripts appearing in the fields "hepatotoxicity" and "drug-induced liver injury" during the calendar year 2008. The most clinically relevant English language case reports and studies exploring mechanisms and risk factors for DILI were then chosen for review, and supplemented with older literature where appropriate.

CONCLUSIONS

As in past years, 2008 was replete with publications dealing with virtually all facets of DILI, including updated incidence and prevalence data, as well as the latest information regarding mechanisms of liver injury. Data from the first 300 patients in the National Institute of Health-sponsored DILI Network registry of > 100 non-acetaminophen causes were presented. Antimicrobials and CNS drugs were responsible for > 60% of cases, with herbals and dietary supplements being increasingly reported. Identification of genetic predispositions to DILI is coming of age with the FDA calling for the testing of human leukocyte antigen B(*)5701 before the use of abacavir to reduce the risk of hypersensitivity reactions. Several groups emphasized the pitfalls in utilizing Roussel Uclaf Causality Assessment Method and other causality assessment methodologies, and an updated review appeared on the use of potentially hepatotoxic medications in patients with underlying liver disease.

Comparison of the 20-hour intravenous and 72-hour oral acetylcysteine protocols for the treatment of acute acetaminophen poisoning

STUDY OBJECTIVE

To compare outcomes after acute acetaminophen poisoning in 2 large cohorts of patients treated with either the 20-hour intravenous or 72-hour oral acetylcysteine protocol.

METHODS

We conducted a retrospective cohort study with historical control comparing patients treated with one of 2 acetylcysteine regimens. Data for the 20-hour group were obtained from a medical record review of patients on whom the 20-hour intravenous protocol was initiated in Canadian hospitals from 1980 to 2005. The 72-hour group consisted of a historical cohort of patients treated in US hospitals with the 72-hour oral protocol from 1976 to 1985. The primary outcome was hepatotoxicity (aminotransferase levels >1,000 IU/L).

RESULTS

Of the 4,048 patients analyzed, 2,086 were in the 20-hour group and 1,962 were in the 72-hour group. The incidence of hepatotoxicity was 13.9% in the 20-hour group and 15.8% in the 72-hour group (-1.9% absolute difference; 95% confidence interval [CI] -4.2 to 0.3). The relative risk of hepatotoxicity was lower in the 20-hour group when acetylcysteine was initiated within 12 hours of ingestion. The relative risk was lower in the 72-hour group when acetylcysteine was initiated later than 18 hours after ingestion. There was no significant risk difference between groups when acetylcysteine treatment was started 12 to 18 hours after ingestion. One patient in the 20-hour group received a liver transplant and died because of acetaminophen toxicity compared with no liver transplants and 3 deaths in the 72-hour group. Anaphylactoid reactions to intravenous acetylcysteine were reported in 148 of 2,086 patients (7.1%; 95% CI 6.1% to 8.3%). This study is limited by comparison of 2 separate data sets from different countries and study years.

CONCLUSION

The risk of hepatotoxicity differed between the 20-hour and 72-hour protocols according to the time to initiation of acetylcysteine. It favored the 20-hour protocol for patients presenting early and favored the 72-hour protocol for patients presenting late after acute acetaminophen overdose.

Patterns of antiepileptic drug overdose differ between men and women: admissions to the Edinburgh Poisons Unit, 2000-2007

BACKGROUND AND AIMS

Antiepileptic drugs are increasingly used in patients with psychiatric disorders who are at increased risk of self-harm. This might increase the likelihood that these agents are used as a means of overdose. This study was designed to examine the rate of occurrence of antiepileptic drug overdose between 2000 and 2007.

METHODS

A retrospective observational study examined patterns of antiepileptic drug overdose in patients admitted to the Edinburgh Poisons Unit, and compared prescription data for the corresponding region. Data were compared using chi-square trend tests.

RESULTS

There were 18 010 admissions to the Toxicology Unit, and 613 patients ingested at least one antiepileptic drug (3.4%). The most frequently implicated were carbamazepine, sodium valproate, phenytoin and lamotrigine, which corresponded with those most commonly prescribed. Women were more likely to ingest lamotrigine than men (P < 0.0001), and less likely to ingest sodium valproate (P = 0.0234). Patients that ingested antiepileptic drugs were more likely to be admitted to hospital for >1 day (22% vs. 8%, P < 0.0001) and need transfer to a psychiatric facility (14% vs. 7%, P < 0.0001).

CONCLUSIONS

Patients that ingested antiepileptic drugs required more intensive medical and psychiatric intervention compared to ingestion of other agents. Significant gender differences were noted in the specific antiepileptic drug ingested. Further work is required to establish whether this discrepancy may be explained by gender-based prescribing practices.

Acute liver impairment after sodium valproate overdose

Liver impairment is a recognised adverse effect of long-term sodium valproate treatment, but there are few reports concerning its occurrence after acute overdose. This report describes a 36-year-old woman who deliberately ingested 32 g of sodium valproate (Epilim). Serum valproate concentration was 4370 μmol/l (630 mg/l) at 4.3 h post-ingestion (therapeutic reference range: 300-600 μmol/l), and the elimination half-life was 14.1 h. Liver biochemistry tests were initially normal but gradually became impaired, and highest alanine aminotransferase (761 U/l) occurred 2.3 days after ingestion. Supportive measures alone were sufficient to allow recovery of liver function. This case indicates that sodium valproate overdose may cause acute hepatocellular injury, even in the absence of pre-existing liver disease.

Review article: The use of potentially hepatotoxic drugs in patients with liver disease

BACKGROUND

Misconceptions surround the use of hepatotoxic drugs in chronic liver disease. While many prescription and over-the-counter (OTC) agents can be used safely, this often runs counter to labelled warnings/contraindications, especially for the statins and other commonly used agents.

AIM

To evaluate published data on the use of hepatotoxic drugs in chronic liver disease including pharmacokinetic changes in cirrhosis and drug interactions, where available, to formulate recommendations on their use.

METHODS

Using a combination of PubMed searches, review texts, the Physicians' Desk Reference and expert opinion, drugs considered at higher risk of hepatotoxicity in chronic liver disease were evaluated.

RESULTS

Most drugs and OTC products including herbals have not been formally studied in chronic liver disease, but available data suggest that several of the most commonly used agents, especially the statins, can be used safely. While there is an increased risk of drug-induced liver injury for drugs used in the treatment of tuberculosis and HIV patients with hepatitis B or C, recommendations for their safe use are emerging.

CONCLUSIONS

Although many clinicians remain hesitant to use hepatotoxic drugs in chronic liver disease, the database supporting this view is limited to just a few agents. Most medications can be used safely in patients with chronic liver disease with appropriate monitoring.