Outcomes from massive paracetamol overdose: a retrospective observational study

Rapid identification of potential nonsteroidal anti-inflammatory drug overdose-induced liver toxicity and prediction of follow-up exposure: Integrating bioanalytical and population pharmacokinetic assay

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most frequently used drugs that can cause liver toxicity. The aim of this study was to integrate bioanalytical and population pharmacokinetic (PopPK) assay to rapidly screen and quantify the concentrations of NSAIDs in plasma and monitor clinical safety. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous quantification of acetaminophen (APAP), flurbiprofen (FLB), aspirin (ASP), and ibuprofen (IBP), four commonly used NSAIDs. The PopPK model of the signature toxicant was analyzed based on the published literature. The LC-MS/MS method was successfully validated and applied to determine NSAID concentrations in patient plasma samples. APAP, ASP, and IBP data were best fitted using a one-compartment model, and FLB data were best fitted using a two-compartment model. Bootstrapping and visual predictive checks suggested that a robust and reliable pharmacokinetic model was developed. A fast, simple, and sensitive LC-MS/MS method was developed and validated for determining APAP, FLB, ASP, and IBP in human plasma. Combined with the PopPK model, this method was applied to rapidly analyze the concentrations of NSAIDs in clinical samples from patients presenting to the emergency department with acute liver dysfunction and monitored NSAIDs clinical safety.

A novel approach to low-cost, rapid and simultaneous colorimetric detection of multiple analytes using 3D printed microfluidic channels

This research paper presents an inventive technique to swiftly create microfluidic channels on distinct membrane papers, enabling colorimetric drug detection. Using a modified DIY RepRap 3D printer with a syringe pump, microfluidic channels (µPADs) are crafted on a flexible nylon-based substrate. This allows simultaneous detection of four common drugs with a single reagent. An optimized blend of polydimethylsiloxane (PDMS) dissolved in hexane is used to create hydrophobic channels on various filter papers. The PDMS-hexane mixture infiltrates the paper's pores, forming hydrophobic barriers that confine liquids within the channels. These barriers are cured on the printer's hot plate, controlling channel width and preventing spreading. Capillary action drives fluid along these paths without spreading. This novel approach provides a versatile solution for rapid microfluidic channel creation on membrane papers. The DIY RepRap 3D printer integration offers precise control and faster curing. The PDMS-hexane solution accurately forms hydrophobic barriers, containing liquids within desired channels. The resulting microfluidic system holds potential for portable, cost-effective drug detection and various sensing applications.

Paracetamol (acetaminophen) poisoning: The early years

Paracetamol (acetaminophen) was marketed in the 1950s as a nonprescription analgesic/antipyretic without any preclinical toxicity studies. It became used increasingly for self-poisoning, particularly in the UK and was belatedly found to cause acute liver damage, which could be fatal. Management of poisoned patients was difficult as maximum abnormalities of liver function were delayed for 3 days or more after an overdose. There was no treatment and the mechanism of hepatotoxicity was not known. The paracetamol half-life was prolonged with liver damage occurring when it exceeded 4 h and the Rumack-Matthew nomogram was an important advance that allowed stratification of patients into separate zones of risk. It is used to guide prognosis and treatment and its predictive value could be increased by combining it with the paracetamol half-life. The problems of a sheep farmer in Australia in the early 1970s led to the discovery of the mechanism of paracetamol hepatotoxicity, and the first effective treatment of overdosage with intravenous (IV) cysteamine. This had unpleasant side effects and administration was difficult. N-acetylcysteine soon became the treatment of choice for paracetamol overdose and given early it was very effective when administered either IV or orally. N-acetylcysteine could cause anaphylactoid reactions, particularly early during IV administration when the concentrations were highest. Simpler and shorter regimes with slower initial rates of infusion have now been introduced with a reduced incidence of these adverse effects. In addition, there has been a move to use larger doses of N-acetylcysteine given over longer periods for patients who are more severely poisoned and those with risk factors. There has been much interest recently in the search for novel biomarkers such as microRNAs, procalcitonin and cyclophilin that promise to have greater specificity and sensitivity than transaminases. Paracetamol-protein adducts predict hepatotoxicity and are specific biomarkers of toxic paracetamol metabolite exposure. Another approach would be measurement of the plasma levels of cysteine and inorganic sulfate. It is 50 years since the first effective treatment for paracetamol poisoning and, apart from liver transplantation, there is still no effective treatment for patients who present late.

Fifty years of paracetamol (acetaminophen) poisoning: the development of risk assessment and treatment 1973-2023 with particular focus on contributions published from Edinburgh and Denver

INTRODUCTION

Fifty years ago, basic scientific studies and the availability of assay methods made the assessment of risk in paracetamol (acetaminophen) poisoning possible. The use of the antidote acetylcysteine linked to new methods of risk assessment transformed the treatment of this poisoning. This review will describe the way in which risk assessment and treatments have developed over the last 50 years and highlight the remaining areas of uncertainty.

METHODS

A search of PubMed and its subsidiary databases revealed 1,166 references published in the period 1963-2023 using the combined terms "paracetamol", "poisoning", and "acetylcysteine". Focused searches then identified 170 papers dealing with risk assessment of paracetamol poisoning, 141 with adverse reactions to acetylcysteine and 114 describing different acetylcysteine regimens. To manage the extensive literature, we focused mainly on contributions made by the authors during their time in Edinburgh and Denver.

DOSE AND CONCENTRATION RESPONSE

The key relationship between paracetamol dose and toxicity risk was established in 1971 and led to the development of the Rumack-Matthew nomogram from data collected in Edinburgh.

MECHANISMS OF TOXICITY

A series of papers on the mechanisms of toxicity were published in 1973, and these showed that paracetamol hepatotoxicity was caused by the formation of a toxic intermediate epoxide metabolite normally detoxified by glutathione but which, in excess, was bound covalently to hepatic enzymes and proteins. An understanding of the relationship between the rate of paracetamol metabolism, paracetamol concentration, and toxic hazard in humans soon followed.

ANTIDOTE DEVELOPMENT AND EFFICACY IN PATIENTS

These discoveries were followed by the testing of a range of sulfhydryl-donors in animals and "at risk" patients. Acetylcysteine was developed as the lead intravenous antidote in the United Kingdom. The license holder in the United States refused to make an intravenous formulation. Thus, oral acetylcysteine became the antidote trialed in the United States National Multicenter Study. Intravenous acetylcysteine regimens used initially in the United Kingdom and subsequently in the United States used loading doses of 150 mg/kg over 15 minutes or one hour, 50 mg/kg over four hours, and 100 mg/kg over 16 hours. These regimens were associated with adverse drug reactions (nausea, vomiting and anaphylactoid reactions) and hence, treatment interruption. Newer dosing regimens now give loading doses more slowly. One, the Scottish and Newcastle Anti-emetic Pretreatment protocol, using an acetylcysteine regimen of 100 mg/kg over two hours followed by 200 mg/kg over 10 hours, has been widely adopted in the United Kingdom. A cohort comparison study suggests this regimen has comparable efficacy to standard regimens and offers opportunities for selective higher acetylcysteine dosing.

RISK ASSESSMENT AT PRESENTATION

No dose-ranging studies with acetylcysteine were done, and no placebo-controlled studies were performed. Thus, there is uncertainty regarding the optimal dose of acetylcysteine, particularly in patients ingesting very large overdoses of paracetamol. The choice of intervention concentration on the Rumack-Matthew nomogram has important consequences for the proportion of patients treated. The United States National Multicenter Study used a "treatment" line starting at 150 mg/L (992 µmol/L) at 4 hours post overdose, extending to 24 hours with a half-life of 4 hours, now standard there, and subsequently adopted in Australia and New Zealand. In the United Kingdom, the treatment line was initially 200 mg/L (1,323 µmol/L) at 4 hours (the Rumack-Matthew "risk" line). In 2012, the United Kingdom Medicines and Healthcare products Regulatory Agency lowered the treatment line to 100 mg/L (662 µmol/L) at 4 hours for all patients, increasing the number of patients admitted and treated at a high cost. Risk assessment is a key issue for ongoing study, particularly following the development of potential new antidotes that may act in those at greatest risk. The development of biomarkers to assess risk is ongoing but has yet to reach clinical trials.

CONCLUSION

Even after 50 years, there are still areas of uncertainty. These include appropriate acetylcysteine doses in patients who ingest different paracetamol doses or multiple (staggered) ingestions, early identification of at-risk patients, and optimal treatment of late presenters.

Avoiding falsely low creatinine concentrations measured in patients treated with N-acetylcysteine for acetaminophen intoxication using enzymo-amperometric method - An in vitro and in vivo study

BACKGROUND

Circulating creatinine is a biomarker of paramount importance in clinical practice. In cases of acetaminophen (APAP) intoxication, the antidote, N-acetylcysteine (NAC), interferes with commonly used creatininase-peroxidase methods. This study aimed to assess whether creatininase-amperometric methods were affected in this context.

METHODS

This study includes in vitro interference tests, involving four creatinine assays using NAC-spiked plasma pools and an in vivo retrospective study comparing creatininase-peroxidase and creatininase-amperometric measurements in patients presenting with NAC-treated APAP poisoning.

RESULTS

Creatininase-peroxidase method was impacted by NAC interference in a clinically-significant manner at therapeutic NAC levels (basal value recovery of 80 % and 70 % for 500 and 1000 mg.L-1 of NAC, respectively), surpassing the desirable Reference Change Value (RCV%). Enzymo-amperometric methods were not impacted. Among patients, a mean bias of -45.2 ± 28.0 % was observed for the peroxidase detection method compared to the amperometric in those who received NAC prior plasma sampling and -2.7 ± 5.4 % in those who did not.

CONCLUSIONS

Our findings indicate that enzymo-amperometric creatinine assays remain unaffected by NAC interference due to the absence of the peroxidase step in the analytical process. Therefore, these methods are suitable to prevent spurious hypocreatininemia in APAP intoxicated patients undergoing NAC therapy.

An international survey of the treatment of massive paracetamol overdose in 2023

INTRODUCTION

Changes in the commercialization of nonprescription drugs have made large quantities of paracetamol available to individuals, resulting in larger overdoses than previously observed. Although most patients with paracetamol overdose can be managed with acetylcysteine, patients with a massive overdose may become critically ill earlier and fail standard antidotal therapy. Several strategies are proposed for the management of these patients, including using increased doses of acetylcysteine, extracorporeal removal, and fomepizole. However, the benefits of these strategies remain largely theoretical, with sparse evidence for efficacy in humans.

METHODS

This cross-sectional study surveys international practice patterns of medical toxicology providers regarding the management of a hypothetical patient with a massive paracetamol overdose.

RESULTS

A total of 342 responses from 31 different nations were obtained during the study period. Sixty-one percent of providers would have increased their acetylcysteine dosing when treating the hypothetical massive overdose. Thirty percent of respondents recommended an indefinite infusion of acetylcysteine at 12.5 mg/kg/hour after the bolus dose, whereas 20 percent recommended following the "Hendrickson" protocol, which advocates for a stepwise increase in acetylcysteine dosing to match high paracetamol concentrations at the 300 mg/L, 400 mg/L, and 600 mg/L lines on the Rumack-Matthew nomogram. Ten percent of respondents stated they would have given "double dose acetylcysteine" but did not specify what that entailed. Forty-seven percent of respondents indicated that they would have given fomepizole, and 28 percent of respondents recommended extracorporeal removal.

DISCUSSION

Our survey study assessed the approach to a hypothetical patient with a massive paracetamol overdose and demonstrated that, at minimum, most respondents would increase the dose of acetylcysteine. Additionally, almost half would also include fomepizole, and nearly one-third would include extracorporeal removal.

CONCLUSIONS

There is considerable international variation for the treatment of both non-massive and massive paracetamol overdoses. Future research is needed to identify and standardize the most effective treatment for both non-massive and massive paracetamol overdoses.

Late N-acetylcysteine for successful recovery of acetaminophen-related acute liver failure: A case report

Acetaminophen toxicity is one of the leading causes of liver failure. Although N-acetylcysteine (NAC) is generally successful in preventing acetaminophen hepatotoxicity when given in a timely manner, if not prescribed in the early golden time, the only practical way to save the patient might be liver transplantation. The case presented was a 20-year-old female with an acetaminophen overdose (30 g), for which more than 24 h had passed since the ingestion. Despite the critical clinical condition, loss of consciousness (Glasgow Coma Score of 4) of the patient, and passing the golden time of antidote administration, the decision was made by the healthcare team to administer NAC. After transferring the patient to the intensive care unit, the three-bag NAC regimen was initiated and appropriate monitoring was performed. After this, the regimen of 3 g q8h was continued for the patient. The patient's condition began to improve slowly on the second day and then she was extubated on the fourth day. Finally, she was discharged on the tenth day. Although the golden period of antidote administration had passed outwardly, there was no need for a liver transplant and the patient recovered successfully with late NAC administration. Hence, clinicians can benefit from the use of NAC even in the late phases of acetaminophen liver toxicity.

Management of Acetaminophen Poisoning in the US and Canada: A Consensus Statement

Importance

The US and Canada currently have no formal published nationwide guidelines for specialists in poison information or emergency departments for the management of acetaminophen poisoning, resulting in significant variability in management.

Objective

To develop consensus guidelines for the management of acetaminophen poisoning in the US and Canada.

Evidence Review

Four clinical toxicology societies (America's Poison Centers, American Academy of Clinical Toxicology, American College of Medical Toxicology, and Canadian Association of Poison Control Centers) selected participants (n = 21). Led by a nonvoting chairperson using a modified Delphi method, the panel created a decision framework and determined the appropriate clinical management of a patient with acetaminophen poisoning. Unique to this effort was the collection of guidelines from most poison centers in addition to systematic collection and review of the medical literature. Comments from review by external organizations were incorporated before the guideline was finalized. The project began in March 2021 and ended in March 2023.

Findings

The search retrieved 84 guidelines and 278 publications. The panel developed guidelines for emergency department management of single or repeated ingestion of acetaminophen. In addition, the panel addressed extended-release formulation, high-risk ingestion, coingestion of anticholinergics or opioids, age younger than 6 years, pregnancy, weight greater than 100 kg, and intravenous acetaminophen use. Differences from current US practice include defining acute ingestion as an ingestion presentation from 4 to 24 hours after overdose was initiated. A revised form of the Rumack-Matthew nomogram was developed. The term massive ingestion was replaced with the term high-risk ingestion and denoted by a specific nomogram line. Other recommendations include specific criteria for emergency department triage, laboratory evaluation and monitoring parameters, defining the role of gastrointestinal decontamination, detailed management of acetylcysteine treatment, associated adverse effects, and stopping criteria for acetylcysteine treatment, as well as criteria for consultation with a clinical toxicologist. Finally, specific treatment considerations, including acetylcysteine dosing, fomepizole administration, and considerations for extracorporeal elimination and transplant evaluation, were addressed.

Conclusions and Relevance

This qualitative study provides a consensus statement on consistent evidence-based recommendations for medical, pharmacy, and nursing education and practice to optimize care of patients with acetaminophen poisoning.

Acetaminophen Metabolites on Presentation Following an Acute Acetaminophen Overdose (ATOM-7)

Acetaminophen (APAP) is commonly taken in overdose and can cause acute liver injury via the toxic metabolite NAPQI formed by cytochrome (CYP) P450 pathway. We aimed to evaluate the concentrations of APAP metabolites on presentation following an acute APAP poisoning and whether these predicted the subsequent onset of hepatotoxicity (peak alanine aminotransferase > 1,000 U/L). The Australian Toxicology Monitoring (ATOM) study is a prospective observational study, recruiting via two poison information centers and four toxicology units. Patients following an acute APAP ingestion presenting < 24 hours post-ingestion were recruited. Initial samples were analyzed for APAP metabolites, those measured were the nontoxic glucuronide (APAP-Glu) and sulfate (APAP-Sul) conjugates and NAPQI (toxic metabolite) conjugates APAP-cysteine (APAP-Cys) and APAP-mercapturate (APAP-Mer). The primary outcome was hepatotoxicity. In this study, 200 patients were included, with a median ingested dose of 20 g, 191 received acetylcysteine at median time of 5.8 hours post-ingestion. Twenty-six patients developed hepatotoxicity, one had hepatotoxicity on arrival (excluded from analysis). Those who developed hepatotoxicity had significantly higher total CYP metabolite concentrations: (36.8 μmol/L interquartile range (IQR): 27.8-51.7 vs. 10.8 μmol/L IQR: 6.9-19.5) and these were a greater proportion of total metabolites (5.4%, IQR: 3.8-7.7) vs. 1.7%, IQR: 1.3-2.6, P < 0.001)]. Furthermore, those who developed hepatotoxicity had lower APAP-Sul concentrations (49.1 μmol/L, IQR: 24.7-72.2 vs. 78.7 μmol/L, IQR: 53.6-116.4) and lower percentage of APAP-Sul (6.3%, IQR: 4.6-10.9 vs. 13.1%, IQR, 9.1-20.8, P < 0.001)]. This study found that those who developed hepatotoxicity had higher APAP metabolites derived from CYP pathway and lower sulfation metabolite on presentation. APAP metabolites may be utilized in the future to identify patients who could benefit from increased acetylcysteine or newer adjunct or research therapies.

Fomepizole should not be used more liberally in paracetamol overdose

Fomepizole is a promising new treatment for preventing liver injury following paracetamol (acetaminophen) overdose. However, we need robust clinical trials to be performed to demonstrate its effect on clinical outcomes that are important to our patients and important to healthcare providers. Until such trials are performed, the toxicology community should learn the lessons from the COVID pandemic-potential novel therapeutic options may be theoretically appealing, but their effectiveness needs to be assessed in robust clinical trials before they are used in clinical practice.

Renoprotective Effect of Taxifolin in Paracetamol-Induced Nephrotoxicity: Emerging Evidence from an Animal Model

BACKGROUND

Taxifolin (TXF) is a flavonoid found abundantly in citrus/onion. Encouraging results on its renoprotective effect have been reported in a limited number of drug-induced nephrotoxicity animal models. The present study aimed to evaluate for the first time the potential renoprotective effects of TXF in a paracetamol (PAR)-induced nephrotoxicity rat model.

METHODS

Rats were divided into three equal groups (n = 6 animals per group). Group 1 (PAR group, PARG) received PAR diluted in normal saline by gavage (1000 mg/kg). Group 2 (TXF group, TXFG) received TXF diluted in normal saline by gavage (50 mg/kg) one hour after PAR administration. Group 3 (control group, CG) received normal saline. Twenty-four hours after PAR administration, all animals were sacrificed using high-dose anesthesia. Blood samples were collected and kidneys were removed.

RESULTS

The serum blood urea nitrogen, creatinine levels and serum malondialdehyde levels were significantly increased in the PARG. The serum glutathione peroxidase, glutathione reductase and total glutathione levels were significantly higher in the TXFG. At the same time, the kidneys of the PARG animals demonstrated tubular epithelium swelling, distension and severe vacuolar degeneration. The kidneys of the TXFG animals showed mildly dilated/congested blood vessels.

CONCLUSIONS

The TXF renoprotective effects are promising in preventing PAR-induced nephrotoxicity, mainly through antioxidant activity, and warrant further testing in future studies.

Large paracetamol overdose-Higher dose acetylcysteine is required

Paracetamol poisoning continues to be a worldwide problem and, despite the availability of an effective antidote, acetylcysteine (NAC), the optimal way to use this antidote, particularly following very large doses of paracetamol, has not been established. Recent case series have shown an increased toxicity from high doses of paracetamol, even in those receiving prompt NAC therapy, particularly in patients above the 300 mg/L nomogram treatment line. Clinical trial evidence supporting shorter NAC dosing now allows the possibility for intensifying treatment without the risk of very high rates of ADRs. New biomarkers also show the possibility of early identification of patients at risk of liver injury who might also benefit from increased intensity treatment. This article discusses these data and proposes a logical therapy for increasing NAC dosing which now requires clinical trial testing.

Large paracetamol overdose - Higher dose NAC is NOT required

Paracetamol overdose is common in developed countries but less than 10% involve large ingestions exceeding 30 g or 500 mg/kg. High dose acetylcysteine (NAC) has been proposed in patients taking large paracetamol overdoses based on reports of hepatotoxicity despite early initiation of NAC treatment with the commonly used 300 mg/kg intravenous acetylcysteine regimen. The evidence from cohorts of patients treated with the standard NAC regimen after large paracetamol overdoses shows that it is effective in most patients. A small study in patients with paracetamol overdoses of 40 g or more and paracetamol concentrations above the 300 mg/L nomogram line showed that modification of the standard NAC regimen to provide a total of 400-500 mg/kg NAC over 21-22 h may reduce the risk of hepatotoxicity (peak ALT > 1000 IU/L) but the impact on development of hepatic failure, liver transplantation and mortality with this approach is presently unknown. Better risk stratification of patients taking paracetamol overdose may allow higher dose NAC and adjunctive treatments such as CYP2E1 inhibition and extracorporeal removal of paracetamol to be targeted to those patients at the highest risk of hepatotoxicity after a large paracetamol 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.

Successful management of delayed presentation of massive paracetamol overdose in a resource‐limited setting: A case report from Nepal

We present a case of self‐poisoning with a massive dose of paracetamol by a young Nepalese female patient who presented late to our emergency department. This report highlights the successful management of the patient with the extended use of N‐acetylcysteine over 4 days and continuous supportive therapy as required. The case is an example of the management of delayed presentation of a massive paracetamol poisoning in a resource‐limited setting, where intensive care units and hemodialysis facilities are not easily available. However, when available, massive poisoning should always be managed in continuous monitoring units under the expertise of a toxicologist.

Toxicology in the emergency department: what's new?

Intentional and accidental drug overdose, recreational drug use and exposure to toxic substances are common reasons for people presenting to emergency departments. Although the mortality rate associated with these presentations is low in the UK, they can lead to significant morbidity and prolonged hospital admissions.

This review discusses new developments in the management of paracetamol overdose. Several new protocols for the infusion of acetylcysteine, the antidote for paracetamol overdose, have been proposed in the past decade and evaluated in clinical studies. The 12-hour Scottish and Newcastle Acetylcysteine Protocol regimen and 20-hour Australian two-infusion bag protocol have been widely adopted into clinical practice and endorsed in national guidelines because of their shorter duration, reduction in adverse effects and efficacy in treating overdose. This article includes a care pathway that can facilitate the implementation of the Scottish and Newcastle Acetylcysteine Protocol.

This article also discusses the emergency management of ingested button batteries, describes the emerging threat of novel psychoactive substances, and provides an update on new UK antidote guidelines. Further up-to-date guidance on management of clinical toxicology is available to healthcare professionals on the internet database TOXBASE.

Paracetamol perturbs neuronal arborization and disrupts the cytoskeletal proteins SPTBN1 and TUBB3 in both human and chicken in vitro models

Epidemiological studies have linked long-term/high-dose usage of paracetamol (N-acetyl-para-aminophenol, APAP) during pregnancy to adverse neuropsychiatric outcomes, primarily attention-deficit hyperactive disorder (ADHD), in the offspring. Though variable, ADHD has been associated with phenotypic alterations characterized by reductions in grey matter densities and aberrations in structural connectivity, effects which are thought to originate in neurodevelopment. We used embryonic chicken cerebellar granule neurons (CGNs) and neuronally differentiating human NTERA2 cells (NT2Ns) to investigate the in vitro effects of APAP on cell viability, migration, neuritogenesis, and the intracellular levels of various proteins involved in neurodevelopment as well as in the maintenance of the structure and function of neurites. Exposure to APAP ranging from 100 to 1600 μM yielded concentration- and time-dependent reductions in cell viability and levels of neurite arborization, as well as reductions in the levels of the cytoskeletal protein β2-spectrin, with the highest APAP concentration resulting in between 50 and 75% reductions in the aforementioned metrics over the course of 72 h. Exposure to APAP also reduced migration in the NT2Ns but not CGNs. Moreover, we found concentration- and time-dependent increases in punctate aggregation of the cytoskeletal protein β3-tubulin following exposure to APAP in both cell model systems, with the highest APAP concentration approximately doubling the number of aggregates over 72-120 h. Our findings demonstrate that APAP negatively perturbs neurite arborization degree, with concurrent reductions in the protein levels of β2-spectrin and disruption of the integrity of β3-tubulin, both proteins of which play important roles in neuronal structure and function.

Fomepizole as an adjunctive therapy for acetaminophen poisoning: cases reported to the toxicology investigators consortium (ToxIC) database 2015-2020

INTRODUCTION

Fomepizole inhibits formation of toxic acetaminophen (APAP) metabolites and may prevent or reverse mitochondrial toxicity. Given these mechanisms, it may be beneficial in patients with severe APAP toxicity. Current patterns of use for this indication are not well-studied.

METHODS

This is a secondary analysis of patients enrolled in the Toxicology Investigators Consortium (ToxIC) database from January 2015 to July 2020. We queried cases in which APAP was listed as an ingested agent and fomepizole was also administered. We excluded cases in which APAP was not the primary agent, N-acetylcysteine (NAC) was not administered, or fomepizole was explicitly administered for another indication. Additionally, we sent a survey to each ToxIC site that administered fomepizole for APAP toxicity to better understand when, why, and how they were using it for this indication.

RESULTS

Twenty-five cases of fomepizole administration following an APAP ingestion met our inclusion criteria. There were one to four cases per year between 2015 and 2019 and eight cases in 2020. Seventeen of 25 (68%) cases were for a known acute ingestion. Eighteen of 25 (72%) patients developed hepatotoxicity (AST or ALT > 1000 IU/L) and 10 of 25 (40%) developed coagulopathy (PT > 15s). This was an ill patient population, with 18 of 25 (72%) developing metabolic acidosis (pH <7.20), 12 of 25 (48%) were intubated, 9 of 25 (36%) receiving vasopressors, and 6 of 25 (24%) receiving continuous renal replacement therapy. Overall, mortality was 24%.

CONCLUSION

The use of fomepizole is increasing in frequency in a small subset of critically ill and acutely APAP-poisoned patients.

Comparing N-acetylcysteine and 4-methylpyrazole as antidotes for acetaminophen overdose

Acetaminophen (APAP) overdose can cause hepatotoxicity and even liver failure. N-acetylcysteine (NAC) is still the only FDA-approved antidote against APAP overdose 40 years after its introduction. The standard oral or intravenous dosing regimen of NAC is highly effective for patients with moderate overdoses who present within 8 h of APAP ingestion. However, for late-presenting patients or after ingestion of very large overdoses, the efficacy of NAC is diminished. Thus, additional antidotes with an extended therapeutic window may be needed for these patients. Fomepizole (4-methylpyrazole), a clinically approved antidote against methanol and ethylene glycol poisoning, recently emerged as a promising candidate. In animal studies, fomepizole effectively prevented APAP-induced liver injury by inhibiting Cyp2E1 when treated early, and by inhibiting c-jun N-terminal kinase (JNK) and oxidant stress when treated after the metabolism phase. In addition, fomepizole treatment, unlike NAC, prevented APAP-induced kidney damage and promoted hepatic regeneration in mice. These mechanisms of protection (inhibition of Cyp2E1 and JNK) and an extended efficacy compared to NAC could be verified in primary human hepatocytes. Furthermore, the formation of oxidative metabolites was eliminated in healthy volunteers using the established treatment protocol for fomepizole in toxic alcohol and ethylene glycol poisoning. These mechanistic findings, together with the excellent safety profile after methanol and ethylene glycol poisoning and after an APAP overdose, suggest that fomepizole may be a promising antidote against APAP overdose that could be useful as adjunct treatment to NAC. Clinical trials to support this hypothesis are warranted.

Use of fomepizole (4-methylpyrazole) for acetaminophen poisoning: A scoping review

INTRODUCTION

Acetaminophen (paracetamol, APAP) poisoning is a prominent global cause of drug-induced liver injury. While N-acetylcysteine (NAC) is an effective antidote, it has therapeutic limitations in massive overdose or delayed presentation. The objective is to comprehensively review the literature on fomepizole as a potential adjunct antidote for acetaminophen toxicity.

METHODS

A scoping review was performed using standardized search terms from inception through July 2021.

RESULTS

Reports on fomepizole as a therapeutic adjunct for APAP toxicity span heterogeneous types of evidence. Eleven preclinical studies (in vitro and animal), fourteen case reports/series, and one human volunteer study were included. Fomepizole's action is mediated by inhibition of CYP2E1 to prevent oxidant stress generation, and inhibition of c-Jun N-terminal kinase (JNK) to decrease amplification of oxidant stress signaling to mitochondria. Studies have shown a reduction in oxidative metabolites likely by shunting metabolism away from CYP2E1 and a resultant decrease in liver injury in animals, independent of CYP2E1 interactions. Fomepizole has been linked to few adverse effects.

CONCLUSION

Based on in vitro and animal studies, and bolstered by case reports, fomepizole likely offers benefit as an adjunct antidote for APAP toxicity, however this remains to be shown in a human trial. NAC remains the standard of care antidote, but given that fomepizole is approved and generally safe, it may be considered for APAP toxicity as off-label use by experienced clinicians, in rare circumstances associated with increased risk of hepatotoxicity despite standard NAC dosing. The marginal clinical benefit of fomepizole adjunct therapy beyond NAC monotherapy remains to be clearly defined, and routine use for APAP overdose is premature based on current evidence.

Comparing development of liver injury using the two versus three bag acetylcysteine regimen despite early treatment in paracetamol overdose

INTRODUCTION

Some studies have reported that early administration of acetylcysteine using a 3-bag regimen may not fully prevent development of liver injury in some patients. We compared the incidence of acute liver injury (ALI) in patients receiving acetylcysteine within eight hours of ingestion between the two-bag acetylcysteine regimen (200 mg/kg over four hours, 100 mg/kg over 16 h) and the three-bag regimen (150 mg/kg over 1 h, 50 mg/kg over 4 h, 100 mg/kg over 16 h).

METHOD

This was a retrospective cohort study of the two-bag and three-bag acetylcysteine regimens from Monash Health, Victoria, Australia (2009-2020), compared to the three-bag acetylcysteine regimen data from the Canadian Acetaminophen Overdose Study (CAOS) database (1980-2005). The inclusion criteria included patients with an acute single ingestion of paracetamol; normal aminotransferases on presentation and acetylcysteine administered within eight hours post-overdose. The primary outcome was development of ALI (defined as: peak aminotransferase >150 IU/L).

RESULTS

At Monash Health, 191 patients were treated with the two-bag acetylcysteine regimen, and 180 patients with the three-bag regimen. The CAOS cohort provided 515 patients treated with the three-bag regimen. ALI developed in 1.6% (3/191) of the two-bag Monash Health group, 2.2% (4/180) of the three-bag Monash Health group (difference -0.6%, p 0.7), and 2.9% (15/515) of the three-bag CAOS group (difference compared to two-bag -1.3%, p 0.4). Hepatotoxicity (ALT >1000) developed in 0.5% (1/191) of patients treated with the two-bag regimen, 1.7% (3/180) in the Monash Health three-bag regimen and 1% (5/515) of the three-bag CAOS group. There were no statistically significant differences between groups.

CONCLUSIONS

ALI and hepatotoxicity were observed in a small, comparable percentage of patients despite early acetylcysteine administration using the two-bag and three-bag regimens. Repeating blood tests at the end of acetylcysteine treatment will identify these patients and indicate those requiring continuation of acetylcysteine.

Evaluation of N-acetylcysteine dose for the treatment of massive acetaminophen ingestion

METHODS

The use of N-acetylcysteine (NAC) remains the standard of care for treatment of acetaminophen (APAP) toxicity and overdose. Currently, there is growing evidence to suggest that massive acetaminophen overdose is associated with increased hepatotoxicity despite timely administration of NAC. This raises the question as to whether an increased dose of intravenous (IV) NAC should be used in the setting of massive APAP ingestion. This study aimed to evaluate the rate of hepatotoxicity after massive APAP overdose treated with 3 different NAC treatment regimens.

METHODS

This was a retrospective cohort study conducted by electronic medical record review of cases reported to a statewide poison control system between 2007 and 2020. Inclusion criteria were single APAP or APAP combination-medication ingestion; acute massive acetaminophen (APAP) ingestion (defined as APAP concentration ≥ 2 times above the Rumack-Matthew 150 nomogram); received one of the three NAC regimens: standard dose IV NAC, oral (PO) NAC, or high dose IV NAC. The risk of hepatotoxicity was evaluated using a multivariate logistic regression model with standard dose IV NAC as the base variable for comparison.

RESULTS

A total of 373 patients met inclusion for the study. Of those, 135 cases were treated with standard dose IV NAC, 121 cases treated with PO NAC, and 117 cases treated with high dose IV NAC. The risk of developing hepatotoxicity was not statistically significant between the high dose IV NAC (OR 1.05, 95% CI 0.52 - 2.09) or oral NAC (OR 0.69, 95% CI 0.33 - 1.46) when compared to standard dose IV NAC. When adjusted for APAP combination medications, initial APAP ratio, initial elevated AST/ALT, and treatment within 8 h, there remained no difference between treatment regimens.

CONCLUSION

This study was unable to detect a large absolute reduction in the rate of hepatotoxicity after massive APAP ingestion in patients treated with high dose IV NAC or PO NAC when compared to standard dose IV NAC; even when treatment was initiated within 8 h of ingestion.

Paracetamol toxicity in mild overdose in combination with opioids: A retrospective observational study

AIMS

Toxicity in paracetamol overdose with opioid co-ingestion is poorly understood. We compared outcomes in both paracetamol-only and paracetamol-opioid overdoses to determine whether toxicity differed significantly between the groups, and to assess the utility of the ratio of measured plasma paracetamol concentration relative to the 4-hour nomogram-adjusted level (APAP_pl /APAP_t ).

METHODS

We conducted a retrospective observational study of all patients (n = 1159) presenting to 2 large UK hospitals between 2005 and 2013 with acute single-dose ingestion paracetamol overdose, with (n = 221) or without (n = 938) opioid co-ingestion. Adverse outcomes included biomarkers of hepatotoxicity and the need for extended treatment. Several outcomes were assessed in relation to the APAP_pl /APAP_t ratio.

RESULTS

Median ingested dose of paracetamol was low in both groups (10 g). Statistical comparison of the median APAP_pl /APAP_t ratios showed a significant difference (0.65 vs. 0.56 for the paracetamol-only and paracetamol-opioid groups respectively, P = .0329). Although there was a trend towards a lower risk of predefined toxic outcomes with opioid co-ingestion, statistical analysis did not show a significant difference, with outcomes for the paracetamol-only and paracetamol-opioid groups including the following: alanine transaminase >2× upper limit of normal, 7.7 vs. 5.7% (P = .6480); alanine transaminase >1000 IU/L, 2.4 vs. 0% (P = .2145); international normalised ratio > 1.3, 8.6 vs. 4.4% (P = .2774); and transfer to tertiary liver unit, 0.2 vs. 0% (P nonsignificant).

CONCLUSION

Our study does not support a change in current clinical practise beyond standard testing at 4 hours or longer post ingestion for mixed low dose paracetamol-opioid overdose.

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.

Risk Factors for Hepatotoxicity Due to Paracetamol Overdose in Adults

Background and Objectives: Over-the-counter availability and a good safety profile make paracetamol one of the most common analgesics in developed countries but also the leading cause of liver failure due to overdose. The objectives of the study were to identify modifiable risk factors for severe hepatotoxicity following paracetamol overdose in adults. Materials and Methods: A retrospective cohort study involved the consecutive adult patients hospitalized in a toxicological center over a period of seven years due to paracetamol overdose. Complete medical datasets of laboratory and anamnestic variables were analyzed and validated by means of logistic regression model. Results: A total of 185 patients entered the study, including 25 individuals who developed severe hepatotoxicity (plasma aminotransferases levels above 1000 UI/L) and 31 individuals with mild to moderate liver injury (plasma aminotransferases levels above upper normal range, but below 1000 UI/L). In the univariable analysis, significant hepatotoxicity risk factors were male gender, alcohol abuse, an ingested paracetamol dose, and a timespan from ingestion to hospital admission. The later one was the only significant risk factor in the multivariable model (adjusted odds ratio 1.08; 95% CI: 1.03-1.12). Conclusions: A delay in hospital admission, resulting in a delayed administration of disease-specific treatment outweighs any other known risk factors of paracetamol-induced hepatotoxicity.

Breast cancer fibroblasts and cross-talk

The breast tumor microenvironment is one of the crucial elements supporting breast cancer tumor progression and metastasis. The fibroblasts are the chief cellular component of the stromal microenvironment and are pathologically activated and differentiated into breast cancer-associated fibroblasts (CAFs). The catabolic phenotype of breast CAFs arises due to metabolic reprogramming of these fibroblasts under pseudo-hypoxic conditions. The metabolic intermediates and ATP produced by the breast CAFs are exploited by the neighboring cancer cells for energy generation. The growth factors, cytokines, and chemokines secreted by the CAFs help fuel tumor growth, invasion, and dissemination. Moreover, the interplay between breast CAFs and cancer cells, mediated by the growth factors, ROS, metabolic intermediates, exosomes, and catabolite transporters, aids in building a favorable microenvironment that promotes cancer cell proliferation, tumor progression, and metastasis. Therefore, identifying effective means to target the reprogrammed metabolism of the breast CAFs and the cross-communication between CAFs and cancer cells serve as promising strategies to develop anti-cancer therapeutics. Henceforth, the scope of the present review ranges from discussing the underlying characteristics of breast CAFs, mechanisms of metabolic reprogramming in breast CAFs, and the nature of interactions between breast CAFs and cancer cells to studying the intricacies of reprogrammed metabolism targeted cancer therapy.

Massive Acetaminophen Overdose Treated Successfully with N-Acetylcysteine, Fomepizole, and Hemodialysis

Acetaminophen overdose is one of the most common causes of acute hepatic failure in the developed world. There is strong evidence for N-acetylcysteine (NAC) as a safe and effective antidote for acetaminophen toxicity. However, there is less clarity in the management of massive overdoses (acute, single ingestions > 500 mg/kg with 4-hour equivalent concentrations ~6000 μmol/L) which are often associated with metabolic acidosis and multiorgan dysfunction. In such ingestions, the role of adjuvant treatments such as fomepizole and extracorporeal removal is unclear. We present a case of a 20-year-old female presenting with an acute ingestion of over 120 grams (1764.7 mg/kg) and an acetaminophen concentration of 5880 μmol/L who developed refractory shock, decreased level of consciousness, and metabolic acidosis requiring mechanical ventilation and vasopressor support. She was treated with gastric decontamination with activated charcoal, IV NAC, fomepizole, and hemodialysis. The patient had complete clearance of acetaminophen by 32 hours after presentation and normalization of her acid base and hemodynamic status without any organ failure. This case highlights the potential benefit of a triple strategy of NAC, fomepizole, and early hemodialysis in massive acetaminophen overdose, potentially sparing complications of prolonged intubation and ICU hospitalization.

An artificial intelligence algorithm for analyzing acetaminophen-associated toxic hepatitis

INTRODUCTION

Very little artificial intelligence (AI) work has been performed to investigate acetaminophen-associated hepatotoxicity. The objective of this study was to develop an AI algorithm for analyzing weighted features for toxic hepatitis after acetaminophen poisoning.

METHODS

The medical records of 187 patients with acetaminophen poisoning treated at Chang Gung Memorial Hospital were reviewed. Patients were sorted into two groups according to their status of toxic hepatitis. A total of 40 clinical and laboratory features recorded on the first day of admission were selected for algorithm development. The random forest classifier (RFC) and logistic regression (LR) were used for artificial intelligence algorithm development.

RESULTS

The RFC-based AI model achieved the following results: accuracy = 92.5 ± 2.6%; sensitivity = 100%; specificity = 60%; precision = 92.3 ± 3.4%; and F1 = 96.0 ± 1.8%. The area under the receiver operating characteristic curve (AUROC) was approximately 0.98. The LR-based AI model achieved the following results: accuracy = 92.00 ± 2.9%; sensitivity = 100%; specificity = 20%; precision = 92.8 ± 3.4%; recall = 98.8 ± 3.4%; and F1 = 95.6 ± 1.5%. The AUROC was approximately 0.68. The weighted features were calculated, and the 10 most important weighted features for toxic hepatitis were aspartate aminotransferase (ALT), prothrombin time, alanine aminotransferase (AST), time to hospital, platelet count, lymphocyte count, albumin, total bilirubin, body temperature and acetaminophen level.

CONCLUSION

The top five weighted features for acetaminophen-associated toxic hepatitis were ALT, prothrombin time, AST, time to hospital and platelet count.

Acute liver failure following paracetamol overdose

Background

Acute liver failure is a rare syndrome comprising a coagulopathy of liver origin, jaundice and encephalopathy in a patient with no prior history of liver disease. Paracetamol overdose is the leading cause of acute liver failure in the United Kingdom and often presents with extrahepatic organ dysfunction requiring critical care. Presentation: We present the case of a patient with hyper acute liver failure secondary to paracetamol overdose. Management and discussion: Management focused on ensuring the correct diagnosis had been made, administering N-acetyl cysteine, fluid resuscitation and broad spectrum antimicrobials. Early intubation and transfer to a transplant centre were undertaken following development of hepatic encephalopathy. Neuroprotective measures and hypertonic saline were instituted to reduce the risk of intracranial hypertension. High dose haemofiltration was also started to help reduce ammonia levels. Aggressive critical care therapies with specialised input results in good outcomes for patients admitted with paracetamol induced hyper acute liver failure. Liver transplant is reserved for those patients unlikely to survive with medical treatment alone.

Clinical outcome of massive acetaminophen overdose treated with standard-dose N-acetylcysteine

BACKGROUND

Recent recognition of "massive" acetaminophen (APAP) overdoses has led to the question of whether standard dosing of N-acetylcysteine (NAC) is adequate to prevent hepatoxicity in these patients. The primary aim of this study was to evaluate the clinical outcome for patients with massive APAP overdose who received standard intravenous NAC dosing of 300 mg/kg over 21 h.

METHODS

This was a single-center retrospective cohort study conducted by chart review of APAP overdoses reported to a regional poison center from 1 January 2010 to 31 December 2019. Massive APAP overdose was defined by single, acute overdose resulting in an APAP concentration exceeding 300 mcg/mL at 4 h post-ingestion. Standard univariate statistical analysis was conducted to describe the cohort, and a multivariate logistic model was utilized to calculate adjusted odds ratios for risk of hepatoxicity.

RESULTS

1425 cases of APAP overdose were reviewed. 104 cases met the inclusion criteria of massive APAP overdose. Overall, 79 cases (76%) had no acute liver injury or hepatotoxicity, and 25 (24%) developed hepatoxicity. Nine percent (n = 4) of cases receiving NAC within 8 h developed hepatotoxicity. Crude odds for hepatoxicity was 5.5-fold higher for cases who received NAC after 8 h.

CONCLUSIONS

Standard NAC dosing received within 8 h prevented hepatoxicity in 91% (n = 40) of cases in our series of massive APAP overdoses. Additional data is needed to determine the clinical outcomes of massive APAP overdose using current intravenous NAC dosing.

The potential protective role of folic acid against acetaminophen-induced hepatotoxicity and nephrotoxicity in rats

Folic acid (FA), is a group B vitamin, has high reactive oxygen radicals quenching ability, resulting in protection against oxidative damage in aerobic cell. Acetaminophen (N-acetyl-p-aminophenol, APAP) is a nonsteroidal anti-inflammatory drug, and can promote oxidative damage in liver and kidney tissues. The aim of this study was to investigate whether folic acid has protective effects on oxidative liver and kidney injury caused by experimental APAP toxication. Forty female Sprague dawley rats were divided into 5 groups; control, APAP, FA, APAP+FA, and APAP+N-acetylcysteine (NAC) groups. APAP toxication was induced by oral gavage (3 g/kg bodyweight). FA (20 mg/kg bodyweight) and NAC (150 mg/kg bodyweight) were given by oral gavage to the specified groups. Oxidant and antioxidant parameter were determined in liver and kidney tissues. In addition, the liver and kidney tissues were histological evaluated. When compared with APAP group, superoxide dismutase (SOD) and catalase activities and glutathione levels were statistically higher, malondialdehyde (MDA) level and myeloperoxidase activity (except liver tissue) were statistically lower in both APAP+FA and APAP+NAC. Liver and kidney MDA level and kidney SOD activity were significantly lower in APAP+NAC group compared with APAP+FA group. Co-administration of NAC with APAP was found to provide protection, but hepatic cords were defective in some places and some glomerular tubules also had dilatation. Necrotic areas was reduced in the liver and the glomerular structure was in good condition in the APAP+FA group. As a result, FA might have a protective effect against APAP-induced hepato-nephrotoxicity and oxidative stress in rat.

A quarter pound of acetaminophen with propylene glycol on the side: A case report

Particularly large acetaminophen overdoses, termed massive, create a therapeutic challenge given the standardized, N-acetylcysteine-based treatment. One consideration in addition to N-acetylcysteine is the initiation of hemodialysis due to the dialyzable nature of acetaminophen, though encumbered by the concurrent removal of the antidote, N-acetylcysteine. Such cases of large acetaminophen overdose, along with possible concomitant ingestions of other drugs or inactive ingredients, can be complicated by challenging-to-interpret clinical signs and laboratory findings. We describe a case of a 46-year-old man for whom we were consulted regarding consideration of dialysis treatment 7 hours after ingestion of 125 g of acetaminophen. The patient developed multiple early signs and laboratory findings consistent with a significant acetaminophen overdose. He also developed a rarely described, likely acetaminophen-interference-induced laboratory abnormality. Finally, he possibly had toxicity from an “inactive” ingredient. He was treated with a single session of prolonged hemodialysis (9.5 hours) and increased dosing of N-acetylcysteine with a positive outcome. Herein, we discuss the decision making and interpretation of clinical data pertaining to dialysis treatment and other therapies after a massive acetaminophen overdose.

Early acetaminophen-protein adducts predict hepatotoxicity following overdose (ATOM-5)

BACKGROUND & AIMS

Acetaminophen-protein adducts are specific biomarkers of toxic acetaminophen (paracetamol) metabolite exposure. In patients with hepatotoxicity (alanine aminotransferase [ALT] >1,000 U/L), an adduct concentration ≥1.0 nmol/ml is sensitive and specific for identifying cases secondary to acetaminophen. Our aim was to characterise acetaminophen-protein adduct concentrations in patients following acetaminophen overdose and determine if they predict toxicity.

METHODS

We performed a multicentre prospective observational study, recruiting patients 14 years of age or older with acetaminophen overdose regardless of intent or formulation. Three serum samples were obtained within the first 24 h of presentation and analysed for acetaminophen-protein adducts. Acetaminophen-protein adduct concentrations were compared to ALT and other indicators of toxicity.

RESULTS

Of the 240 patients who participated, 204 (85%) presented following acute ingestions, with a median ingested dose of 20 g (IQR 10-40), and 228 (95%) were treated with intravenous acetylcysteine at a median time of 6 h (IQR 3.5-10.5) post-ingestion. Thirty-six (15%) patients developed hepatotoxicity, of whom 22 had an ALT ≤1,000 U/L at the time of initial acetaminophen-protein adduct measurement. Those who developed hepatotoxicity had a higher initial acetaminophen-protein adduct concentration compared to those who did not, 1.63 nmol/ml (IQR 0.76-2.02, n = 22) vs. 0.26 nmol/ml (IQR 0.15-0.41; n = 204; p <0.0001), respectively. The AUROC for hepatotoxicity was 0.98 (95% CI 0.96-1.00; n = 226; p <0.0001) with acetaminophen-protein adduct concentration and 0.89 (95% CI 0.82-0.96; n = 219; p <0.0001) with ALT. An acetaminophen-protein adduct concentration of 0.58 nmol/ml was 100% sensitive and 91% specific for identifying patients with an initial ALT ≤1,000 U/L who would develop hepatotoxicity. Adding acetaminophen-protein adduct concentrations to risk prediction models improved prediction of hepatotoxicity to a level similar to that obtained by more complex models.

CONCLUSION

Acetaminophen-protein adduct concentration on presentation predicted which patients with acetaminophen overdose subsequently developed hepatotoxicity, regardless of time of ingestion. An adduct threshold of 0.58 nmol/L was required for optimal prediction.

LAY SUMMARY

Acetaminophen poisoning is one of the most common causes of liver injury. This study examined a new biomarker of acetaminophen toxicity, which measures the amount of toxic metabolite exposure called acetaminophen-protein adduct. We found that those who developed liver injury had a higher initial level of acetaminophen-protein adducts than those who did not.

CLINICAL TRIAL REGISTRATION

Australian Toxicology Monitoring (ATOM) Study-Australian Paracetamol Project: ACTRN12612001240831 (ANZCTR) Date of registration: 23/11/2012.

The Effect of 4-Methylpyrazole on Oxidative Metabolism of Acetaminophen in Human Volunteers

INTRODUCTION

Acetaminophen (APAP) is commonly ingested in both accidental and suicidal overdose. Oxidative metabolism by cytochrome P450 2E1 (CYP2E1) produces the hepatotoxic metabolite, N-acetyl-p-benzoquinone imine. CYP2E1 inhibition using 4-methylpyrazole (4-MP) has been shown to prevent APAP-induced liver injury in mice and human hepatocytes. This study was conducted to assess the effect of 4-MP on APAP metabolism in humans.

METHODS

This crossover trial examined the ability of 4-MP to inhibit CYP2E1 metabolism of APAP in five human volunteers. Participants received a single oral dose of APAP 80 mg/kg, both with and without intravenous 4-MP, after which urinary and plasma oxidative APAP metabolites were measured. The primary outcome was the fraction of ingested APAP excreted as total oxidative metabolites (APAP-CYS, APAP-NAC, APAP-GSH).

RESULTS

Compared with APAP alone, co-treatment with 4-MP decreased the percentage of ingested APAP recovered as oxidative metabolites in 24-hour urine from 4.48 to 0.51% (95% CI = 2.31-5.63%, p = 0.003). Plasma concentrations of these oxidative metabolites also decreased.

CONCLUSIONS

These results show 4-MP effectively reduced oxidative metabolism of APAP in human volunteers ingesting a supratherapeutic APAP dose.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03878693.

Safety and Efficacy of the SNAP 12-hour Acetylcysteine Regimen for the Treatment of Paracetamol Overdose

BACKGROUND

Acetylcysteine (NAC) is effective at preventing liver injury after paracetamol overdose. The Scottish and Newcastle Anti-emetic Pre-treatment for Paracetamol Poisoning (SNAP) Study demonstrated that a 12 h NAC regimen was associated with fewer adverse drug reactions compared with the standard 21 h regimen. Here, we describe the clinical effectiveness of the SNAP NAC regimen.

METHODS

The SNAP regimen, consisting of intravenous NAC 100 mg/kg over 2 h then 200 mg/kg over 10 h, was introduced to treat all paracetamol overdose patients at the Royal Infirmary of Edinburgh, the Royal Victoria Infirmary, Newcastle and St Thomas' Hospital, London. Patient data were prospectively and systematically collected before and after the change in treatment (total patients N = 3340, 21 h N = 1488, SNAP N = 1852). Health record linkage was used to determine patient outcome after hospital discharge.

FINDINGS

There was no difference in liver injury or liver synthetic dysfunction between regimens. Hepatotoxicity (peak ALT > 1000 U/L) occurred in 64 (4.3%) and 67 (3.6%) patients, respectively, in the 21 h and SNAP groups (absolute difference - 0.7%, 95% CI - 2.1 to 0.6). Multivariable logistic regression did not identify treatment regimen as an outcome-associated factor. No patients were readmitted to hospital with, or died from, liver failure within 30 days of discharge. Anti-histamine treatment (for NAC anaphylactoid drug reactions) was prescribed for 163 (11.0%) patients with the 21 h regimen and 37 (2.0%) patients with the SNAP regimen (absolute difference 9.0% (95% CI 7.3 to 10.7)).

INTERPRETATION

In clinical use the SNAP regimen has similar efficacy as standard therapy for preventing liver injury and produces fewer adverse reactions.

MicroRNA from a 12-h versus 20-h acetylcysteine infusion for paracetamol overdose

Paracetamol overdose is common and microRNA (miR)-122 expression is increased with liver injury. We aimed to measure miR-122 in the setting of an abbreviated paracetamol overdose treatment regimen. We compared miRNA expression in patients treated for paracetamol poisoning with an abbreviated 12-h intravenous acetylcysteine regimen (200 mg/kg over 4 h, 50 mg/kg over 8 h) or a 20-h regimen (200 mg/kg over 4 h, 100 mg/kg over 16 h) (NACSTOP trial). miR-122 expression is increased (decreased cycle threshold (Ct) values) with paracetamol liver injury. We assessed miR-122 expression in patients receiving the two acetylcysteine regimens and in a separate group with acute liver injury (ALI). We examined 121 blood samples in 38 patients. After 20 h of acetylcysteine, median alanine transaminase (ALT) was 12 U/L (18, 14) versus 16 U/L (11, 21) ( p = 0.17) and median miR-122 Ct was 30.1 (interquartile range (IQR): 28.9, 33.3) versus 31.4 (28.9, 33.9) ( p = 0.7) in the NACSTOP abbreviated and control groups, respectively. Median normalized miR-122 Ct after 20 h of acetylcysteine was 2.2 (IQR 1.9, 6.4), 1.1 (0.7, 2.9), 63.9 (2.5, 168), 123.2 (40.9, 207.8) in the NACSTOP-abbreviated, NACSTOP-control, ALI and hepatotoxicity groups, respectively. There was no significant difference in ALT or miRNA between NACSTOP treatment groups and no signal of increased liver injury from an abbreviated 12-h acetylcysteine regimen. These findings suggest that an abbreviated acetylcysteine regimen in low-risk patients who have overdosed on paracetamol is safe. Further study is required to validate this finding utilizing miRNA as a comparative biomarker.

The NACSTOP Trial: A Multicenter, Cluster-Controlled Trial of Early Cessation of Acetylcysteine in Acetaminophen Overdose

Historically, intravenous acetylcysteine has been delivered at a fixed dose and duration of 300 mg/kg over 20 to 21 hours to nearly every patient deemed to be at any risk for hepatotoxicity following acetaminophen overdose. We investigated a 12-hour treatment regimen for selected low-risk patients. This was a multicenter, open-label, cluster-controlled trial at six metropolitan emergency departments. We enrolled subjects following single or staggered acetaminophen overdose with normal serum alanine transaminase (ALT) and creatinine on presentation and at 12 hours, and less than 20 mg/L acetaminophen at 12 hours. Patients were allocated to intervention (250 mg/kg over 12-hour) or control (300 mg/kg over 20-hour) regimens by site. The primary outcome was incidence of "hepatic injury" 20 hours following initiation of acetylcysteine treatment, defined as ALT doubling and peak ALT greater than 100 IU/L, indicating the need for further antidotal treatment. Secondary outcomes included incidence of hepatotoxicity (ALT > 1,000 IU/L), peak international normalized ratio (INR), and adverse drug reactions. Of the 449 acetaminophen overdoses receiving acetylcysteine, 100 were recruited to the study. Time to acetylcysteine (median 7 hours [interquartile ratio 6,12] versus 7 hours [6,10]) and initial acetaminophen (124 mg/L [58,171] versus 146 mg/L [66,204]) were similar between intervention and control groups. There was no difference in ALT (18 IU/L [13,22] versus 16 IU/L [13,21]) or INR (1.2 versus 1.2) 20 hours after starting acetylcysteine between groups. No patients developed hepatic injury or hepatotoxicity in either group (odds ratio 1.0 [95% confidence interval 0.02, 50]). No patients represented with liver injury, none died, and 96 of 96 were well at 14-day telephone follow-up. Conclusion: Discontinuing acetylcysteine based on laboratory testing after 12 hours of treatment is feasible and likely safe in selected patients at very low risk of liver injury from acetaminophen overdose.

Paracetamol metabolite concentrations following low risk overdose treated with an abbreviated 12-h versus 20-h acetylcysteine infusion

CONTEXT

To compare degree of liver injury and paracetamol metabolite concentrations after treatment with standard of care (20-h) vs. abbreviated (12-h) acetylcysteine regimens used in paracetamol overdose (NACSTOP trial).

METHODS

Timed blood samples from a cohort of subjects enrolled in the cluster-controlled NACSTOP trial evaluating a 12-h acetylcysteine regimen (200 mg/kg over 4 h, 50 mg/kg over 8 h) were assayed for paracetamol metabolites as a pilot study, using liquid chromatography/mass spectrometry. Control group subjects received a 20-h course of acetylcysteine (200 mg/kg over 4 h, 100 mg/kg over 16 h). The intervention group received a 12-h acetylcysteine regimen (stopped after at least 12 h of treatment). Positive control groups not in the trial with acute liver injury (ALI) or hepatotoxicity were also studied.

RESULTS

One hundred and forty-one blood samples were collected from 40 patients receiving acetylcysteine after paracetamol overdose. Median ALT after 20 h of acetylcysteine was 12 U/L (IQR 8.14) in the abbreviated regimen group, compared to the control group 16 U/L (IQR 11.21) (p = .46). There was no significant difference in median metabolite concentrations on presentation and after 20 h of acetylcysteine between these two groups (p > .05). Presentation median sum CYP-metabolite/total metabolite percentages were 2.5 and 3.0 in the abbreviated and control NACSTOP groups, respectively.

CONCLUSIONS

An abbreviated 12-h acetylcysteine regimen for paracetamol overdose used in the NACSTOP trial had similar circulating metabolite concentrations compared to a 20-h regimen in selected subjects with low risk of hepatotoxicity. This suggests that further acetylcysteine may not be needed in the abbreviated group at time of cessation.

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.

Metabolic coupling and the Reverse Warburg Effect in cancer: Implications for novel biomarker and anticancer agent development

Glucose is a key metabolite used by cancer cells to generate ATP, maintain redox state and create biomass. Glucose can be catabolized to lactate in the cytoplasm, which is termed glycolysis, or alternatively can be catabolized to carbon dioxide and water in the mitochondria via oxidative phosphorylation. Metabolic heterogeneity exists in a subset of human tumors, with some cells maintaining a glycolytic phenotype while others predominantly utilize oxidative phosphorylation. Cells within tumors interact metabolically with transfer of catabolites from supporting stromal cells to adjacent cancer cells. The Reverse Warburg Effect describes when glycolysis in the cancer-associated stroma metabolically supports adjacent cancer cells. This catabolite transfer, which induces stromal-cancer metabolic coupling, allows cancer cells to generate ATP, increase proliferation, and reduce cell death. Catabolites implicated in metabolic coupling include the monocarboxylates lactate, pyruvate, and ketone bodies. Monocarboxylate transporters (MCT) are critically necessary for release and uptake of these catabolites. MCT4 is involved in the release of monocarboxylates from cells, is regulated by catabolic transcription factors such as hypoxia inducible factor 1 alpha (HIF1A) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and is highly expressed in cancer-associated fibroblasts. Conversely, MCT1 is predominantly involved in the uptake of these catabolites and is highly expressed in a subgroup of cancer cells. MYC and TIGAR, which are genes involved in cellular proliferation and anabolism, are inducers of MCT1. Profiling human tumors on the basis of an altered redox balance and intra-tumoral metabolic interactions may have important biomarker and therapeutic implications. Alterations in the redox state and mitochondrial function of cells can induce metabolic coupling. Hence, there is interest in redox and metabolic modulators as anticancer agents. Also, markers of metabolic coupling have been associated with poor outcomes in numerous human malignancies and may be useful prognostic and predictive biomarkers.

Massive paracetamol overdose: an observational study of the effect of activated charcoal and increased acetylcysteine dose (ATOM-2)

CONTEXT

Paracetamol is commonly taken in overdose, with increasing concerns that those taking "massive" overdoses have higher rates of hepatotoxicity and may require higher doses of acetylcysteine. The objective was to describe the clinical characteristics and outcomes of "massive" (≥ 40 g) paracetamol overdoses.

METHODS

Patients were identified through the Australian Paracetamol Project, a prospective observational study through Poisons Information Centres in NSW and Queensland, over 3 and 1.5 years, respectively, and retrospectively from three clinical toxicology unit databases (over 2.5 to 20 years). Included were immediate-release paracetamol overdoses ≥ 40 g ingested over ≤ 8 h. Outcomes measured included paracetamol ratio[defined as the ratio of the first paracetamol concentration taken 4-16 h post-ingestion to the standard (150 mg/L at 4 h) nomogram line at that time] and hepatotoxicity (ALT >1000 U/L).

RESULTS

Two hundred paracetamol overdoses were analysed, reported median dose ingested was 50 g (interquartile range (IQR): 45-60 g) and median paracetamol ratio 1.9 (IQR: 1.4-2.9, n = 173). One hundred and ninety-three received acetylcysteine at median time of 6.3 h (IQR: 4-9.3 h) post-ingestion. Twenty-eight (14%) developed hepatotoxicity, including six treated within 8 h of ingestion. Activated charcoal was administered to 49(25%), at median of 2 h post-ingestion (IQR:1.5-5 h). Those receiving activated charcoal (within 4 h of ingestion), had significantly lower paracetamol ratio versus those who did not: 1.4 (n = 33, IQR: 1.1-1.6) versus 2.2 (n = 140, IQR: 1.5-3.0) (p < .0001) (paracetamol concentration measured ≥ 1 h after charcoal). Furthermore, they had lower rates of hepatotoxicity [unadjusted OR: 0.12 (95% CI: <0.001-0.91); adjusted for time to acetylcysteine OR: 0.20 (95%CI: 0.002-1.74)]. Seventy-nine had a paracetamol ratio ≥2, 43 received an increased dose of acetylcysteine in the first 21 h; most commonly a double dose in the last bag (100 to 200 mg/kg/16 h). Those receiving increased acetylcysteine had a significant decrease risk of hepatotoxicity [OR:0.27 (95% CI: 0.08-0.94)]. The OR remained similar after adjustment for time to acetylcysteine and paracetamol ratio.

CONCLUSION

Massive paracetamol overdose can result in hepatotoxicity despite early treatment. Paracetamol concentrations were markedly reduced in those receiving activated charcoal within 4 h. In those with high paracetamol concentrations, treatment with increased acetylcysteine dose within 21 h was associated with a significant reduction in hepatotoxicity.

Outcomes from massive paracetamol overdose: a retrospective observational study

LINKED ARTICLE

This article is commented on by Bateman DN and Dear JW. Should we treat very large paracetamol overdose differently? Br J Clin Pharmacol 2017; 83: 1163-5. https://doi.org/10.1111/bcp.13279 AIMS: Treatment of paracetamol (acetaminophen) overdose with acetylcysteine is standardized, with dose determined only by patient weight. The validity of this approach for massive overdoses has been questioned. We systematically compared outcomes in massive and non-massive overdoses, to guide whether alternative treatment strategies should be considered, and whether the ratio between measured timed paracetamol concentrations (APAP_pl ) and treatment nomogram thresholds at those time points (APAP_t ) provides a useful assessment tool.

METHODS

This is a retrospective observational study of all patients (n = 545) between 2005 and 2013 admitted to a tertiary care toxicology service with acute non-staggered paracetamol overdose. Massive overdoses were defined as extrapolated 4-h plasma paracetamol concentrations >250 mg l^-1 , or reported ingestions ≥30 g. Outcomes (liver injury, coagulopathy and kidney injury) were assessed in relation to reported dose and APAP_pl :APAP_t ratio (based on a treatment line through 100 mg l^-1 at 4 h), and time to acetylcysteine.

RESULTS

Ingestions of ≥30 g paracetamol correlated with higher peak serum aminotransferase (r = 0.212, P < 0.0001) and creatinine (r = 0.138, P = 0.002) concentrations. Acute liver injury, hepatotoxicity and coagulopathy were more frequent with APAP_pl :APAP_t  ≥ 3 with odds ratios (OR) and 95% confidence intervals (CI) of 9.19 (5.04-16.68), 35.95 (8.80-158.1) and 8.34 (4.43-15.84), respectively (P < 0.0001). Heightened risk persisted in patients receiving acetylcysteine within 8 h of overdose.

CONCLUSION

Patients presenting following massive paracetamol overdose are at higher risk of organ injury, even when acetylcysteine is administered early. Enhanced therapeutic strategies should be considered in those who have an APAP_pl :APAP_t  ≥ 3. Novel biomarkers of incipient liver injury and abbreviated acetylcysteine regimens require validation in this patient cohort.