Updates on acetaminophen toxicity

Disposable Nafion-Coated Single-Walled Carbon Nanotube Test Strip for Electrochemical Quantitative Determination of Acetaminophen in a Finger-Prick Whole Blood Sample

A disposable electrochemical test strip for the quantitative point-of-care (POC) determination of acetaminophen (paracetamol) in plasma and finger-prick whole blood was fabricated. The industrially scalable dry transfer process of single-walled carbon nanotubes (SWCNTs) and screen printing of silver were combined to produce integrated electrochemical test strips. Nafion coating stabilized the potential of the Ag reference electrode and enabled the selective detection in spiked plasma as well as in whole blood samples. The test strips were able to detect acetaminophen in small 40 μL samples with a detection limit of 0.8 μM and a wide linear range from 1 μM to 2 mM, well within the required clinical range. After a simple 1:1 dilution of plasma and whole blood, a quantitative detection with good recoveries of 79% in plasma and 74% in whole blood was achieved. These results strongly indicate that these electrodes can be used directly to determine the unbound acetaminophen fraction without the need for any additional steps. The developed test strip shows promise as a rapid and simple POC quantitative acetaminophen assay.

A Study on the Medication Errors in the Administration of N-Acetylcysteine for Paracetamol Overdose Patients in Malaysia

Introduction

N-Acetylcysteine (NAC) has been used to treat paracetamol overdose for four decades. But the administration of NAC regimens is complicated. Therefore, medication errors are an ongoing issue in the acute-care setting and directly impact the safety of patients.

Objective

To evaluate the rate of NAC-related medication errors during the management of paracetamol overdose at a teaching hospital in Malaysia.

Methods

This clinical audit study was performed retrospectively between June 2008 and June 2011. Patients who presented to the adult emergency department with paracetamol overdose and had received at least the loading dose of intravenous NAC were eligible. Children below the age of 12 years old were not included. Also, patients displaying chronic excessive paracetamol usage or recurrent paracetamol overdose were excluded. We determined the type and frequency of medication errors during intravenous NAC administration.

Results

The study population ranged from 13 to 87 years old (mean age: 25.06; median: 23) and was predominantly female. The overall prevalence of intravenous NAC-related medication errors was found to be 84.3%. Moreover, the following frequencies were observed based on error type: 5.9% wrong dose, 37.3% incorrect infusion rate, 8.5% interruption during treatment, and 66.5% unnecessary administration.

Conclusion

We observe a surprisingly high prevalence of medication errors related to the administration of intravenous NAC. Thus, this emerging issue needs be addressed in order to ensure patient safety as well as to prevent unnecessary hospital admissions and/or burdening treatment costs. (Hong Kong j.emerg.med. 2014;21: 361-367)

Drug-Induced Liver Injury: Cascade of Events Leading to Cell Death, Apoptosis or Necrosis

Drug-induced liver injury (DILI) can broadly be divided into predictable and dose dependent such as acetaminophen (APAP) and unpredictable or idiosyncratic DILI (IDILI). Liver injury from drug hepatotoxicity (whether idiosyncratic or predictable) results in hepatocyte cell death and inflammation. The cascade of events leading to DILI and the cell death subroutine (apoptosis or necrosis) of the cell depend largely on the culprit drug. Direct toxins to hepatocytes likely induce oxidative organelle stress (such as endoplasmic reticulum (ER) and mitochondrial stress) leading to necrosis or apoptosis, while cell death in idiosyncratic DILI (IDILI) is usually the result of engagement of the innate and adaptive immune system (likely apoptotic), involving death receptors (DR). Here, we review the hepatocyte cell death pathways both in direct hepatotoxicity such as in APAP DILI as well as in IDILI. We examine the known signaling pathways in APAP toxicity, a model of necrotic liver cell death. We also explore what is known about the genetic basis of IDILI and the molecular pathways leading to immune activation and how these events can trigger hepatotoxicity and cell death.

Paracetamol as a toxic substance for children: aspects of legislation in selected countries

Paracetamol is used widely in pediatrics because it has a high drug safety when used in therapeutic dosages. In case of overdose the majority of paracetamol is metabolized to N-acetyl-p-benzoquinone imine (NAPQI), which is responsible for the severe toxic effects. The covalent connection between NAPQI and hepatic proteins leads to hepatocellular damage and possibly to severe liver failure. The antidote for paracetamol is N-acetylcysteine (NAC). It is a precursor of glutathione and aids to fill glutathione stores. The Rumack-Matthew nomogram should be used to decide on antidote treatment. Pediatric drug metabolism differs from adult metabolism. Children have a larger liver size compared to their body weight than adults, resulting in a higher metabolism rate. Young children seem to be less sensitive to acute intoxication than adults. One hypothesis to explain the lower rate refers to the larger liver size. The acute toxic dosage for children is more than 200 mg/kg body weight. There seems to be a global increase in accidental pediatric paracetamol overdose. Governmental websites of various European Union (EU) countries were searched for legal information on paracetamol availability in pharmacies and non-pharmacy stores. Various EU countries permit prescription-free sales of paracetamol in pharmacies and non-pharmacy stores. In Sweden paracetamol 500 mg may be sold in both pharmacies and non-pharmacies in a maximum pack size of 20 units. In the United Kingdom (UK) paracetamol 500 mg is listed in the general sales list with a maximum pack size of 30 effervescent tablets or 16 tablets. In Ireland paracetamol 500 mg may be sold in a maximum pack size of 12 units in a non-pharmacy. In the Netherlands paracetamol 500 mg is legal to be sold in a maximum pack size of 50 units in a drug store and with a maximum of 20 units in any other non-pharmacy. Several countries in the European Union are permitted to offer paracetamol prescription-free in pharmacies and non-pharmacy stores without legal guidance on the storage position within the store. Further research is needed to investigate whether paracetamol is located directly accessible to young children within the stores in EU countries which permit prescription-free sales of paracetamol.

Pharmacogenomics of acetaminophen in pediatric populations: a moving target

Acetaminophen (APAP) is widely used as an over-the-counter fever reducer and pain reliever. However, the current therapeutic use of APAP is not optimal. The inter-patient variability in both efficacy and toxicity limits the use of this drug. This is particularly an issue in pediatric populations, where tools for predicting drug efficacy and developmental toxicity are not well established. Variability in toxicity between age groups may be accounted for by differences in metabolism, transport, and the genetics behind those differences. While pharmacogenomics has been revolutionizing the paradigm of pharmacotherapy for many drugs, its application in pediatric populations faces significant challenges given the dynamic ontogenic changes in cellular and systems physiology. In this review we focused on the ontogenesis of the regulatory pathways involved in the disposition of APAP and on the variability between pediatric, adolescent, and adult patients. We also summarize important polymorphisms of the pharmacogenes associated with APAP metabolism. Pharmacogenetic studies in pediatric APAP treatment are also reviewed. We conclude that while a consensus in pharmacogenetic management of APAP in pediatric populations has not been achieved, a systems biology based strategy for comprehensively understanding the ontogenic regulatory pathway as well as the interaction between age and genetic variations are particularly necessary in order to address this question.

Robust protein nitration contributes to acetaminophen-induced mitochondrial dysfunction and acute liver injury

Acetaminophen (APAP), a widely used analgesic/antipyretic agent, can cause liver injury through increased nitrative stress, leading to protein nitration. However, the identities of nitrated proteins and their roles in hepatotoxicity are poorly understood. Thus, we aimed at studying the mechanism of APAP-induced hepatotoxicity by systematic identification and characterization of nitrated proteins in the absence or presence of an antioxidant, N-acetylcysteine (NAC). The levels of nitrated proteins markedly increased at 2h in mice exposed to a single APAP dose (350mg/kg ip), which caused severe liver necrosis at 24h. Protein nitration and liver necrosis were minimal in mice exposed to nontoxic 3-hydroxyacetanilide or animals co-treated with APAP and NAC. Mass-spectral analysis of the affinity-purified nitrated proteins identified numerous mitochondrial and cytosolic proteins, including mitochondrial aldehyde dehydrogenase, Mn-superoxide dismutase, glutathione peroxidase, ATP synthase, and 3-ketoacyl-CoA thiolase, involved in antioxidant defense, energy supply, or fatty acid metabolism. Immunoprecipitation followed by immunoblot with anti-3-nitrotyrosine antibody confirmed that the aforementioned proteins were nitrated in APAP-exposed mice but not in NAC-cotreated mice. Consistently, NAC cotreatment significantly restored the suppressed activity of these enzymes. Thus, we demonstrate a new mechanism by which many nitrated proteins with concomitantly suppressed activity promotes APAP-induced mitochondrial dysfunction and hepatotoxicity.

Reliability of the reported ingested dose of acetaminophen for predicting the risk of toxicity in acetaminophen overdose patients

PURPOSE

The present study examines the relationship between the dose of acetaminophen reported to have been ingested by patients and the occurrence of serum acetaminophen levels above the 'possible toxicity' line in patients presenting at the hospital after acetaminophen overdose. The prognostic value of patient-reported dosage cut-offs of 8, 10 and 12 g was determined.

METHODS

This retrospective cohort study included patients admitted to the emergency department or hospital within 24 hours of acetaminophen ingestion. Serum acetaminophen concentrations were considered to be the gold standard, and specificity, sensitivity and positive/negative predictive values were calculated from the reported ingested dose, to predict toxicity using the Rumack-Matthew nomogram (i.e. the 'possible toxicity' treatment line) and standard equations.

RESULTS

Of 305 patients identified, 291 met the study inclusion criteria, and 121 (41.6%) had serum acetaminophen concentrations above the 'possible toxicity' treatment line. The range of patient-reported acetaminophen ingested was 1-75 g, with 185 patients (63.6%) reporting ≥8 g. One hundred eighteen patients (97.5%) who reported ingesting ≥8 g had serum acetaminophen concentrations above the '150-line', compared with only three patients (2.5%) who reported ingesting <8 g (p < 0.001). The positive predictive value of a patient-reported dose ≥8 g for predicting serum acetaminophen concentrations above the 'possible toxicity' treatment line was 63.78%, with a negative predictive value of 97.17%. The sensitivity of patient-reported doses ≥8 g was high (97.52%) but with low specificity (60.59%). The sensitivity of patient-reported doses ≥10 g also was high (89.26%) with low specificity (65.29%), whereas the sensitivity of ≥12 g dose was low (61.16%) with high specificity (86.47%).

CONCLUSIONS

Patient-reported doses of acetaminophen are good risk indicators for acetaminophen overdose patients in Malaysia. Patient-reported ingestion of ≥8 g (as a cut-off dose) had a higher sensitivity than ≥10 g or ≥12 g. The results of this study have important implications for toxicity risk evaluations in areas with poor serum acetaminophen assay availability.

Review article: Drug-induced liver injury--its pathophysiology and evolving diagnostic tools

BACKGROUND

Drug-induced liver injury (DILI) is a significant cause of morbidity and mortality accounting for at least 13% of acute liver failure cases in the US. It is the leading cause of acute liver failure among patients referred for liver transplantation and the most common reason that drugs in development do not obtain FDA approval. The incidence of DILI has been reported to be one in 10,000 to one in 100,000 patients; however, the actual incidence is probably higher due in part to the difficulty of diagnosis.

AIM

To present a review of the current literature on DILI with a focus on its pathophysiology and evolving diagnostic modalities.

METHODS

A PubMed literature search was conducted using the terms 'drug induced liver injury', 'pathophysiology', 'causality', 'diagnosis', 'toxicogenomics' and 'pharmacogenetics'.

RESULTS

Drug-induced liver injury is an area of ongoing research. From the time it was first recognised, our understanding of the pathophysiology, its classification, diagnosis and reporting by established national networks continues to challenge and evolve. Metabonomics, pharmacogenetics, proteomics and transcriptomics are more recent areas of study that have been applied to further the understanding of DILI.

CONCLUSIONS

Despite recent advances in our understanding of drug-induced liver injury, many aspects of its pathophysiology and clinical impact remain unclear. In addition, genomic-based studies are evolving concepts, which undoubtedly continue to contribute to our understanding of the underlying mechanisms of drug-induced liver injury.

Consumption of three most widely used analgesics in six European countries

WHAT IS KNOWN AND OBJECTIVE

Analgesics are among the most widely used drugs and there is wide intercountry variability in the rates of consumption of different analgesics. Our objective is to determine and compare patterns of analgesic consumption in the Slovak Republic and a number of other European countries.

METHODS

We undertook a drug utilization study using WHO ATC/defined daily doses (DDD) methodology. Wholesale analgesic data collected by the Slovak State Institute for Drug Control were used. Utilization was calculated as DDD per 1000 inhabitants per day. Comparison with wholesale data from Czech Republic, Estonia, Finland, Norway and Denmark, published on the Internet, was made.

RESULTS AND DISCUSSION

Paracetamol/acetaminophen consumption varied only a little in Slovak Republic and Czech Republic, whereas consumption in Nordic countries was significantly higher (P < 0.05) and in Estonia significantly lower. Ibuprofen consumption was significantly higher in Czech Republic and Finland. Significantly lower consumption was in Norway. The lowest consumption of ASA/aspirin was in Denmark and in Norway. The highest consumption was in Finland.

WHAT IS NEW AND CONCLUSION

Effective therapy needs good prescribing and well-informed prescribers and patients. Our study highlights wide differences in analgesic consumption even among similar European countries. The basis of these differences and their potential clinical impact require further investigation.

N-acetylcysteine as a novel prophylactic treatment for ifosfamide-induced nephrotoxicity in children: translational pharmacokinetics

Ifosfamide (IFO), which is used in the treatment of pediatric solid tumors, causes high rates of nephrotoxicity. N-acetylcysteine (NAC), an antidote for acetaminophen overdose, has been shown to prevent IFO-induced renal cell death and nephrotoxicity in both LLCPK-1 cells and a rat model. To facilitate the use of NAC in preventing IFO-induced nephrotoxicity in children, the authors compared the systemic exposure to NAC in children treated for acetaminophen overdose to the systemic exposure of the therapeutically effective rat model. The mean systemic exposure in the rat model was 18.72 mM·h (range, 9.92-30.02 mM·h), compared to the mean systemic exposure found in treated children (14.48 mM·h; range, 6.22-32.96 mM·h). They also report 2 pediatric cases in which NAC-attenuated acute renal failure associated with IFO when given concurrently with their chemotherapy treatment. Systemic exposure to NAC measured in 1 of these cases was comparable to that in the children treated for acetaminophen overdose. These results corroborate NAC's potential to protect against IFO-induced nephrotoxicity in children when used in its clinically approved dose schedule and supports a clinical trial in children.

Anti-hepatotoxic effects of 3,4-methylenedioxyphenol and N-acetylcysteine in acutely acetaminophen-overdosed mice

3,4-Methylenedioxyphenol (sesamol) is effective against acetaminophen-induced liver injury in rats. Whether sesamol’s anti-hepatotoxic effect is comparable to that of N-acetylcysteine has never been studied. We investigated the anti-hepatotoxic effects of sesamol and N-acetylcysteine on acetaminophen-induced hepatotoxicity in mice. Equimolar doses (1 mmol/kg) of sesamol and N-acetylcysteine significantly inhibited acetaminophen (300 mg/kg)-increased serum aspartate transaminase and alanine transaminase levels 6 h post-administration. Sesamol and N-acetylcysteine maintained hepatic glutathione levels and inhibited lipid peroxidation. Moreover, the combination of sesamol and N-acetylcysteine antagonistically inhibited sesamol’s protection against acetaminophen-induced liver injury. We conclude that the protective effect of sesamol against acetaminophen-induced liver damage is comparable to that of N-acetylcysteine by maintaining glutathione levels and inhibiting lipid peroxidation in mice.

Epidemiology of idiosyncratic drug-induced liver injury

Idiosyncratic drug-induced liver injury (DILI) is a significant health problem because of its unpredictable nature, poorly understood pathogenesis, and potential to cause fatal outcomes. It is also a significant hurdle for drug development and marketing of safe prescription medications. Idiosyncratic DILI is generally rare, but its occurrence is likely underappreciated due to the lack of active reporting or surveillance systems and substantial challenges involved in its recognition and diagnosis. Nonetheless, DILI is a common cause of potentially serious and fatal acute liver failure in both children and adults. Population-based studies that accurately estimate the incidence and full spectrum of DILI are limited. However, using a prospective, population-based French study with an annual estimated incidence of 13.9 +/- 2.4 DILI cases per 100,000 inhabitants, it has been extrapolated that nearly 44,000 individuals in the United States will suffer from DILI each year. Although increasing numbers of patients are also being seen with DILI due to herbal and dietary supplements, the epidemiology of this entity requires further investigation. In this article, the epidemiology of DILI, both in the general population and in potentially high-risk subgroups, is reviewed.

Acute hepatic failure in an infant caused by acetaminophen (paracetamol) toxicity

A 7-month-old infant developed acute fatal hepatic failure owing to inadvertent duplication of paracetamol prescriptions. Paracetamol toxicity should be considered in the differential diagnosis of infants presenting with acute hepatic failure.

Management of the critically poisoned patient

BACKGROUND

Clinicians are often challenged to manage critically ill poison patients. The clinical effects encountered in poisoned patients are dependent on numerous variables, such as the dose, the length of exposure time, and the pre-existing health of the patient. The goal of this article is to introduce the basic concepts for evaluation of poisoned patients and review the appropriate management of such patients based on the currently available literature.

METHODS

An unsystematic review of the medical literature was performed and articles pertaining to human poisoning were obtained. The literature selected was based on the preference and clinical expertise of authors.

DISCUSSION

If a poisoning is recognized early and appropriate testing and supportive care is initiated rapidly, the majority of patient outcomes will be good. Judicious use of antidotes should be practiced and clinicians should clearly understand the indications and contraindications of antidotes prior to administration.

Acetaminophen hepatotoxicity and acute liver failure

Acetaminophen-induced hepatotoxicity is a common consequence of acetaminophen overdose and may lead to acute liver failure (ALF). Currently acetaminophen is the most common cause of ALF in both United States and United Kingdom, with a trend to increasing incidence in the United States. N-acetylcysteine is the most effective drug to prevent progression to liver failure with acetaminophen hepatotoxicity. Liver transplantation is the only definitive therapy that will significantly increase the chances of survival for advanced ALF. This communication reviews current information regarding causes and management of acetaminophen-induced hepatotoxicity and ALF.

Effects of hemolysis and lipemia on the COBAS salicylate and acetaminophen assays compared to GDS assays

OBJECTIVE

We compared the COBAS(R) acetaminophen and salicylate assays (Roche Diagnostics) with the Stanbio GDS assays (Stanbio Laboratories) that are currently used in our laboratory with respect to interferences from hemolysis and lipemia.

METHODS

Acetaminophen and salicylate were added into human serum with varying concentrations of hemoglobin or Intralipid to generate a range of acetaminophen and salicylate concentrations. Then the COBAS and GDS assays were used to measure the apparent drug concentrations; the H and L indices were measured to determine the extent of hemolysis and lipemia present in each specimen.

RESULTS

Both hemolysis and lipemia have less effect on the COBAS(R) acetaminophen and salicylate assays than on the GDS assays.

CONCLUSIONS

The COBAS assays for acetaminophen and salicylate are preferable to the current GDS assays in clinical toxicology laboratories.

Critical care toxicology

Emergency physicians are regularly called on to care for critically poisoned patients. This article reviews the general approach and management of the critically poisoned patient. Specific clinical characteristics are identified that may clue the clinician into a specific toxin class as a diagnosis. Appropriate testing in the poisoned patient is reviewed. Complications of poisoning that may bring a rapid demise of the critically ill poisoned patient are highlighted and the management of those complications is discussed.

Toxicology in the critical care unit

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

Emerging role of Nrf2 in protecting against hepatic and gastrointestinal disease

Transcription factor NF-E2-related factor 2 (Nrf2) belongs to the basic region-leucine zipper family and is activated in response to electrophiles and reactive oxygen species. Nrf2 coordinately regulates the constitutive and inducible transcription of a wide array of genes involved in drug metabolism, detoxification, and antioxidant defenses. During periods of oxidative stress, Nrf2 is released from sequestration in the cytoplasm and translocates to the nucleus. Nrf2 binds antioxidant response elements (AREs) in the regulatory regions of target genes and activates transcription. Genetically modified mice lacking Nrf2 serve as a useful tool for identifying new ARE-regulated genes and assessing the ability of Nrf2 to confer protection against a variety of pathologies in numerous organs including the liver, intestine, lung, skin, and nervous system. With regards to the liver and gastrointestinal tract, Nrf2 knockout mice are more susceptible to acetaminophen-induced hepatocellular injury, benzo[a]pyrene-induced tumor formation and Fas- and TNFalpha -mediated hepatocellular apoptosis. The higher sensitivity of Nrf2 knockout mice to chemical toxicity is due in part to reduced basal and inducible expression of detoxification enzymes. Nrf2 may also be important in protecting against liver fibrosis, gallstone development, and formation of aberrant crypt foci. Research of Nrf2 has opened up new opportunities in understanding how antioxidant defense pathways are regulated, how oxidative stress contributes to disease progression and may serve as a novel target for designing therapies to prevent and treat diseases in which oxidative stress is implicated.