Paracetamol overdose and hepatotoxicity at a regional Australian hospital: a 4-year experience

Performance of the paracetamol-aminotransferase multiplication product in risk stratification after paracetamol (acetaminophen) poisoning: a systematic review and meta-analysis

BACKGROUND

Risk stratification in paracetamol (acetaminophen) poisoning is crucial because hepatotoxicity is common and can be mitigated with treatment. However, current risk stratification tools have limitations.

AIMS

We evaluated the diagnostic performance of the paracetamol concentration × aminotransferase multiplication product, for predicting hepatotoxicity after paracetamol overdose.

METHODS

Medline, Cochrane Library and Embase were searched for eligible papers. We used random effects models to obtain pooled estimates of the likelihood ratios and diagnostic odds ratios, from which sensitivity and specificity were computed. We assessed two commonly used cut-off values of paracetamol × aminotransferase, 1500 mg/L × IU/L and 10,000 mg/L × IU/L. Using the confusion matrices of these two cut-offs, area under the summary receiver operator characteristic curve and optimal cut-off values in different clinical scenarios were established.

RESULTS

Six studies comprising 5036 participants were included. In 4051 patients, using the cut-off of 1500 mg/L × IU/L, a diagnostic odds ratio of 31.90 (95%CI: 9.52-106.90), sensitivity of 0.98 (95%CI: 0.94-1.00) and specificity of 0.66 (95%CI: 0.49-0.89) were obtained. In 3983 patients, using the cut-off of 10,000 mg/L × IU/L, a diagnostic odds ratio of 99.34 (95%CI: 12.26-804.87), sensitivity of 0.65 (95%CI: 0.51-0.82) and specificity of 0.97 (95%CI: 0.95-1.00) were obtained. For staggered ingestions, the 1500 mg/L × IU/L cut-off yielded a diagnostic odds ratio of 69.53 (95%CI: 4.03-1199.75), sensitivity of 1.00 (95%CI: 0.87-1.00) and specificity of 0.74 (95%CI: 0.43-1.00). Next, using the 10,000 mg/L × IU/L cut-off in this scenario yielded a diagnostic odds ratio of 254.58 (95%CI: 11.12-5827.60), sensitivity of 0.79 (95%CI: 0.59-1.00) and specificity of 0.98 (95%CI: 0.94-1.00). The overall summary receiver operator characteristic curve was 0.91 (95%CI: 0.75-0.97), and the optimal cut-off value was 3840 mg/L × IU/L. The summary receiver operator characteristic curve in patients with staggered ingestions was 0.96 (95%CI: 0.85-0.99). The summary receiver operator characteristic curve in patients with staggered ingestions and whose paracetamol concentration was below the detectable limit of 10 mg/L at presentation was 0.97 (95%CI: 0.94-0.99).

CONCLUSION

In this first meta-analysis, paracetamol × aminotransferase demonstrates its use in prognosticating hepatotoxicity in patients with paracetamol poisoning. It complements the Rumack-Matthew nomogram as it has shown promise in addressing two key limitations of the nomogram: it is usable after more than 24 h between overdose and acetylcysteine treatment, and it is applicable in staggered ingestions.

Epidemiological differences of common liver conditions between Asia and the West

Liver diseases form a heterogenous group of acute and chronic disorders of varying etiologies. Not only do they result in significant morbidity and mortality, but they also lead to a marked reduction in quality of life, together with a high socioeconomic burden globally. A better understanding of their global distribution is necessary to curb the massive health-care and socioeconomic burden that they entail. Notable differences and similarities have been described between common liver disease conditions occurring in Asia and the West (Europe and North America), giving rise to the need for an updated collective appraisal of this subject. In this review, the epidemiological differences of common liver conditions, specifically acute liver failure, drug-induced liver injury, acute-on-chronic liver failure, hepatocellular carcinoma, and non-alcoholic fatty liver disease, between Asia and the West are discussed.

Characteristics and Outcomes of Acetaminophen Overdose and Hepatotoxicity in Thailand

Background and Aims: Acetaminophen (APAP) is the leading cause of drug overdose and hepatotoxicity worldwide, including in Thailand. Patterns of overdose and hospital management are known to have significant impacts on the outcomes of APAP overdose, and these factors vary from country to country. Therefore, this study aimed to analyze clinical characteristics of Thai patients with APAP overdose in terms of overdose patterns, clinical presentation, treatment and outcomes. Methods: In this retrospective analytical study, medical records of adult patients hospitalized with a diagnosis of APAP overdose at Rajavithi Hospital, Bangkok, between January 2013 and December 2017 were reviewed. Results: A total of 184 patients diagnosed with APAP overdose were included. The median age was 22 (15-76) years and the majority were female (79.9%). Most overdoses were intended self-poisoning ingestion (90.8%) with a median dose of 10.5 g (4.5-50). A total of 121 patients were treated with N-acetylcysteine with a median visit-to-N-acetylcysteine time of 2 (0.5-15) h. Overall, 15.6% developed mild hepatotoxicity (aspartate aminotransferase or alanine aminotransferase >3 times the upper limit of normal), 6.4% developed severe hepatotoxicity (aspartate aminotransferase or alanine aminotransferase >10 times the upper limit of normal and international normalized ratio >2.0) and 3 patients developed acute liver failure (1 patient resolved spontaneously and 2 patients, neither of whom had a liver transplant, died). Significant predictors for hepatotoxicity included older age, chronic alcohol drinking, repeated taking of medication for more than 8 h (staggered ingestion), long duration between ingestion and hospital visit, alcohol coingestion, abdominal pain symptoms, and acute kidney injury. Conclusions: Most cases of APAP overdose in Thailand appear to be young women with intentional ingestion. With prompt management, most patients (76.4%) did not develop significant hepatotoxicity; nevertheless, despite N-acetylcysteine therapy, hepatotoxicity including acute liver failure was observed in a small proportion of patients, particularly those with unintentional overdose and chronic alcohol drinking.

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

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

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

Introduction

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

Methods

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

Results

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

Conclusions

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

Characterisation and outcomes of adult patients with paracetamol overdose presenting to a tertiary hospital in Singapore

INTRODUCTION

Paracetamol is the most common pharmaceutical agent implicated in toxic exposure in Singapore. This study aimed to describe the characteristics of paracetamol overdose in the adult population managed at a tertiary healthcare facility in Singapore.

METHODS

Medical records of adult patients hospitalised with a diagnosis of paracetamol overdose at National University Hospital, Singapore, over a three-year period from January 2011 to December 2013 were retrospectively reviewed.

RESULTS

A total of 177 patients had paracetamol overdose. The median age was 25 years, with a significant female predominance (71.2%). Intentional ingestion accounted for the majority (76.8%) of cases. The median dose of paracetamol ingested was 10 (interquartile range 8-15) g. Among patients who reported ingesting more than 10 g, 46.5% perceived the overdose as non-lethal. N-acetylcysteine was administered in 76.3% of patients, among whom 24.4% experienced an anaphylactoid reaction. Of the 10 (5.6%) patients who had severe hepatotoxicity, 2 (1.1%) developed acute liver failure. Most patients had resolving transaminases at discharge and none required liver transplantation. The median length of hospitalisation was three days. There were no fatalities.

CONCLUSION

Paracetamol overdose occurred predominantly in young adults with intentional ingestion, suggesting that preventive measures targeted at promoting public awareness may not suffice. However, the perceived lack of lethality by many patients who ingested potentially toxic amounts of paracetamol reflects a certain knowledge gap. Healthcare providers should proactively educate consumers on the proper use of paracetamol and the consequences of its overdose.

Seasonality in acute liver injury? Findings in two health care claims databases

BACKGROUND

Presumed seasonal use of acetaminophen-containing products for relief of cold/influenza ("flu") symptoms suggests that there might also be a corresponding seasonal pattern for acute liver injury (ALI), a known clinical consequence of acetaminophen overdose.

OBJECTIVE

The objective of this study was to determine whether there were any temporal patterns in hospitalizations for ALI that would correspond to assumed acetaminophen use in cold/flu season.

METHODS

In the period 2002-2010, monthly hospitalization rates for ALI using a variety of case definitions were calculated. Data sources included Truven MarketScan(®) Commercial Claims and Encounters (CCAE) and Medicare Supplemental and Coordination of Benefits (MDCR) databases. We performed a statistical test for seasonality of diagnoses using the periodic generalized linear model. To validate that the test can distinguish seasonal from nonseasonal patterns, we included two positive controls (ie, diagnoses of the common cold [acute nasopharyngitis] and influenza), believed to change with seasons, and two negative controls (female breast cancer and diabetes), believed to be insensitive to season.

RESULTS

A seasonal pattern was observed in monthly rates for common cold and influenza diagnoses, but this pattern was not observed for monthly rates of ALI, with or without comorbidities (cirrhosis or hepatitis), breast cancer, or diabetes. The statistical test for seasonality was significant for positive controls (P<0.001 for each diagnosis in both databases) and nonsignificant for ALI and negative controls.

CONCLUSION

No seasonal pattern was observed in the diagnosis of ALI. The positive and negative controls showed the expected patterns, strengthening the validity of the statistical and visual tests used for detecting seasonality.

Redox Nanoparticle Therapeutics for Acetaminophen-Induced Hepatotoxicity in Mice

The purpose of this study was to evaluate the hepatoprotective effect of an antioxidative nanoparticle (RNP(N)) recently developed against APAP-induced hepatotoxicity in mice. The effects of oral administration of RNP(N) to APAP-treated mice were assessed for various biochemical liver function parameters: alanine transaminase (ALT) activity, aspartate transaminase (AST) activity, alkaline phosphatase (ALP) activity, prothrombin time, and serum albumin (ALB) level. The treatment effects were assessed in terms of free radical parameters: malondialdehyde (MDA) accumulation, glutathione peroxidase (GPx) activity, % inhibition of superoxide anion (O2 (-∙)), and histopathological examination. The N-acetylcysteine (NAC)-treated group exhibited an enhanced prothrombin time relative to the control group, while RNP(N) did not prolong prothrombin time. The RNP(N)-treated animals exhibited lower levels of ALT, AST, and ALP, while increased ALB levels were measured in these animals compared to those in the other groups. The RNP(N)-treated animals furthermore exhibited improved MDA levels, GPx activity, and % inhibition of O2 (-∙), which relate to oxidative damage. Histological staining of liver tissues from RNP(N)-treated animals did not reveal any microscopic changes relative to the other groups. The findings of this study suggest that RNP(N) possesses effective hepatoprotective properties and does not exhibit the notable adverse effects associated with NAC treatment.

Detecting mRNA Predictors of Acetaminophen-Induced Hepatotoxicity in Mouse Blood Using Quantitative Real-Time PCR

Acetaminophen (APAP) is a widely used analgesic and antipyretic drug. Drug-induced liver injury from agents such as APAP is known to vary between individuals within a species. To avoid liver injury and ensure the proper use of pharmaceutical products, it is important to be able to predict such risks using genetic information. This study evaluated the use of quantitative real-time polymerase chain reaction (RT-qPCR) to identify mRNAs (carried in the blood of male ddY mice) capable of predicting susceptibility to APAP-induced hepatotoxicity. Screening was performed on samples obtained at 18 h after treatment from mice that had been orally treated with 500 mg/kg APAP. APAP-induced hepatotoxicity was seen in 60% of the mice, and the mortality rate was 12%. Blood APAP concentration did not differ significantly between mice with and without APAP-induced hepatotoxicity. We compared blood mRNA expression levels between mice with (positive, serious or lethal injury) and without hepatotoxicity in the APAP-treated group. The transcript levels of interleukin-encoding loci Il1β, Il10, and tumor necrosis factor (Tnf) were increased in the lethal injury group. Transcripts of the loci encoding transthyretin (Ttr) and metallothionein 1 (Mt1) showed increases in the liver injury group, while those of the glutathione peroxidase 3-encoding locus (Gpx3) were decreased. APAP hepatotoxicity was potentiated in fasted animals, although fasting did not appear to affect the level of expression of these genes. These results indicate that mRNA expression of Il1β, Il10, Tnf, Ttr, Mt1, and Gpx3 in mouse blood may provide useful surrogate markers of APAP-induced hepatotoxicity.

The use of paracetamol (acetaminophen) among a community sample of people with chronic non-cancer pain prescribed opioids

BACKGROUND

The regular use of simple analgesics in addition to opioids such as paracetamol (or acetaminophen) is recommended for persistent pain to enhance analgesia. Few studies have examined the frequency and doses of paracetamol among people with chronic non-cancer pain including use above the recommended maximum daily dose.

AIMS

To assess (i) the prevalence of paracetamol use among people with chronic non-cancer pain prescribed opioids, (ii) assess the prevalence of paracetamol use above the recommended maximum daily dose and (iii) assess correlates of people who used paracetamol above the recommended maximum daily dose including: age, gender, income, education, pain severity and interference, use of paracetamol/opioid combination analgesics, total opioid dose, depression, anxiety, pain self-efficacy or comorbid substance use, among people prescribed opioids for chronic non-cancer pain.

METHODS

This study draws on baseline data collected for the Pain and Opioids IN Treatment (POINT) study and utilises data from 962 interviews and medication diaries. The POINT study is national prospective cohort of people with chronic non-cancer pain prescribed opioids. Participants were recruited from randomly selected pharmacies across Australia.

RESULTS

Sixty-three per cent of the participants had used paracetamol in the past week (95% CI = 59.7-65.8). Among the paracetamol users 22% (95% CI = 19.3-24.6) had used paracetamol/opioid combination analgesics and 4.8% (95% CI = 3.6-6.3) had used paracetamol above the recommended maximum daily dose (i.e. > 4000 mg/day). Following binomial logistic regression (χ(2) = 25.98, df = 10, p = 0.004), people who had taken above the recommended maximum daily dose were less likely to have low income (AOR = 0.52, 95% CI = 0.27-0.99), more likely to use paracetamol/opioid combination analgesics (AOR = 2.01, 95% CI = 1.02-3.98) and more likely to take a higher opioid dose (AOR = 1.00, 95% CI = 1.00-1.01).

CONCLUSION

The majority of people with chronic non-cancer pain prescribed opioids report using paracetamol appropriately. High income, use of paracetamol/opioid combination analgesics and higher opioid dose were independently associated with paracetamol use above the recommended maximum daily dose.

Emergency department visits for acetaminophen overdose: a Canadian population-based epidemiologic study (1997–2002)

Objective:

We describe the epidemiology of emergency department (ED) visits for acetaminophen overdose in a large Canadian health region, with a focus on sociodemographic risk factors and temporal trends.

Methods:

Patients presenting to an ED in the Calgary Health Region (population ~ 1.1 million) for acetaminophen overdose between 1997 and 2002 were identified using regional administrative data.

Results:

A total of 2699 patients made 3015 ED visits for acetaminophen overdose between 1997 and 2002, corresponding to an age- and sex-adjusted incidence of 45.7 per 100 000 population. Alcohol-related disorders were common (19%) and overdose rates were higher in females, younger patients, Aboriginals and social assistance recipients. The incidence decreased from 52.6 per 100 000 in 1997 to 35.1 per 100 000 in 2002 (34% relative reduction;p&lt; 0.0005). When classified according to suicidal intent, the rates of intentional and unintentional overdose (69% and 25% of all overdoses, respectively) showed similar temporal trends. A marked seasonality was observed, with a peak in spring and early summer.

Conclusions:

ED visit rates for acetaminophen overdose fell between 1997 and 2002. High-risk groups, including young females and marginalized populations, may benefit from preventive and educational initiatives.

[Pediatric perioperative systemic pain therapy: Austrian interdisciplinary recommendations on pediatric perioperative pain management]

BACKGROUND

Many analgesics used in adult medicine are not licensed for pediatric use. Licensing limitations do not, however, justify that children are deprived of a sufficient pain therapy particularly in perioperative pain therapy. The treatment is principally oriented to the strength of the pain. Due to the degree of pain caused, intramuscular and subcutaneous injections should be avoided generally.

NON-OPIOIDS

The basis of systemic pain therapy for children are non-opioids and primarily non-steroidal anti-inflammatory drugs (NSAIDs). They should be used prophylactically. The NSAIDs are clearly more effective than paracetamol for acute posttraumatic and postoperative pain and additionally allow economization of opioids. Severe side effects are rare in children but administration should be carefully considered especially in cases of hepatic and renal dysfunction or coagulation disorders. Paracetamol should only be taken in pregnancy and by children when there are appropriate indications because a possible causal connection with bronchial asthma exists. To ensure a safe dosing the age, body weight, duration of therapy, maximum daily dose and dosing intervals must be taken into account. Dipyrone is used in children for treatment of visceral pain and cholic. According to the current state of knowledge the rare but severe side effect of agranulocytosis does not justify a general rejection for short-term perioperative administration.

OPIOIDS

In cases of insufficient analgesia with non-opioid analgesics, the complementary use of opioids is also appropriate for children of all age groups. They are the medication of choice for episodes of medium to strong pain and are administered in a titrated form oriented to effectiveness. If severe pain is expected to last for more than 24 h, patient-controlled anesthesia should be implemented but requires a comprehensive surveillance by nursing personnel.

KETAMINE

Ketamine is used as an adjuvant in postoperative pain therapy and is recommended for use in pediatric sedation and analgosedation.

Outcomes of patients with acetaminophen-associated toxic hepatitis at a far east poison center

BACKGROUND

There is an overall paucity of data regarding the outcomes of patients with acetaminophen-associated toxic hepatitis in Taiwan. Therefore, the purpose of this study was to recruit a larger number of patients and to examine the clinical features, the degrees of toxic hepatitis, the physiological markers, and the clinical outcomes after intentional acetaminophen poisoning, and to determine what association, if any, might exist between these findings.

METHODS

We examined the medical records of 187 patients with intentional acetaminophen poisoning who were examined at Chang Gung Memorial Hospital between 2000 and 2011. Patients were categorized into 2 groups according to hepatic complications, i.e. with (n = 15) or without (n = 172) toxic hepatitis. Demographic, clinical, and laboratory data were collected, and the mortality rate was analyzed.

RESULTS

It was found that patients with toxic hepatitis had higher serum acetaminophen level (P = 0.007), but they also arrived to the hospital later (P < 0.001) than patients without toxic hepatitis. Furthermore, patients with toxic hepatitis showed higher incidences of acute respiratory failure (P = 0.012) than those shown by patients who did not have hepatitis. The laboratory examinations also revealed greater degrees of granulocytosis (P < 0.001) and poorer liver function tests (P < 0.001) in patients with hepatitis than in patients without hepatitis. Nevertheless, a univariate logistic regression model failed to identify any significant risk factors for toxic hepatitis complication after ingestion (P > 0.05). At the end of the analysis, 1 patient with toxic hepatitis died of liver failure. Finally, there was no significant difference in mortality between patients with and without hepatitis (P = 0.080).

CONCLUSION

The analytical data revealed that toxic hepatitis was not uncommon (15/187 or 8.0%) after acetaminophen overdose. Further studies are warranted.

Pattern recognition analysis for hepatotoxicity induced by acetaminophen using plasma and urinary 1H NMR-based metabolomics in humans

Drug-induced liver injury (DILI) is currently an increasingly relevant health issue. However, available biomarkers do not reliably detect or quantify DILI risk. Therefore, the purpose of this study was to comparatively evaluate plasma and urinary biomarkers obtained from humans treated with acetaminophen (APAP) using a metabolomics approach and a proton nuclear magnetic resonance (NMR) platform. APAP (3 g/day, two 500 mg tablets every 8 h) was administered to 20 healthy Korean males (age, 20-29 years) for 7 days. Urine was collected daily before and during dosing and 6 days after the final dose. NMR spectra of these urine samples were analyzed using principal component analysis (PCA) and partial least-squares-discrimination analysis. Although the activities of aspartate aminotransferase and lactate dehydrogenase were significantly increased 7 days post-APAP treatment, serum biochemical parameters of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total bilirubin, γ-glutamyl transpeptidase, and lactate dehydrogenase were within normal range of hepatic function. However, urine and plasma (1)H NMR spectroscopy revealed different clustering between predosing and after APAP treatment for global metabolomic profiling through PCA. Urinary endogenous metabolites of trimethylamine-N-oxide, citrate, 3-chlorotyrosine, phenylalanine, glycine, hippurate, and glutarate as well as plasma endogenous metabolites such as lactate, glucose, 3-hydroxyisovalerate, isoleucine, acetylglycine, acetone, acetate, glutamine, ethanol, and isobutyrate responded significantly to APAP dosing in humans. Urinary and plasma endogenous metabolites were more sensitive than serum biochemical parameters. These results might be applied to predict or screen potential hepatotoxicity caused by other drugs using urinary and plasma (1)H NMR analyses.

Acetaminophen-related hepatotoxicity

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

A one-year observational study of all hospitalized and fatal acute poisonings in Oslo: epidemiology, intention and follow-up

Background

Up to date information on poisoning trends is important. This study reports the epidemiology of all hospitalized acute poisonings in Oslo, including mortality, follow-up referrals, and whether the introduction of over-the-counter sales of paracetamol outside pharmacies had an impact on the frequency of poisonings.

Methods

All acute poisonings of adults (≥16 years) treated at the five hospitals in Oslo from April 2008 to April 2009 were included consecutively in an observational cross-sectional multicentre study. A standardized form was completed by the treating physician, which covered the study aims. All deaths by poisoning in and outside hospitals were registered at the Institute of Forensic Medicine.

Results

There were 1065 hospital admissions of 912 individuals; 460 (50%) were male, and the median age was 36 years. The annual incidence was 2.0 per 1000. The most frequent toxic agents were ethanol (18%), benzodiazepines (15%), paracetamol (11%), and opioids (11%). Physicians classified 46% as possible or definite suicide attempts, 37% as accidental overdoses with substances of abuse (AOSA), and 16% as other accidents. Twenty-four per cent were discharged without any follow-up and the no follow-up odds were highest for AOSA. There were 117 deaths (eight in hospital), of which 75% were males, and the median age was 41 years. Thus, the annual mortality rate was 25 per 100 000 and the in-hospital mortality was 0.8%. Opioids were the most frequent cause of death.

Conclusions

The incidence of hospitalized acute poisonings in Oslo was similar to that in 2003 and there was an equal sex distribution. Compared with a study performed in Oslo in 2003, there has been an increase in poisonings with a suicidal intention. The in-hospital mortality was low and nine out of ten deaths occurred outside hospitals. Opioids were the leading cause of death, so preventive measures should be encouraged among substance abusers. The number of poisonings caused by paracetamol remained unchanged after the introduction of over-the-counter sales outside pharmacies and there were no deaths, so over-the-counter sales may be considered safe.

Low rates of hepatotoxicity among Asian patients with paracetamol overdose: a review of 1024 cases

Background

The metabolism of paracetamol in Asians is thought to differ from Westerners. Detailed clinical features of paracetamol -induced hepatotoxicity among Asians remains largely unreported.

Methods

A retrospective review of adult cases with paracetamol overdose over a five-year duration was performed in two of the largest public institutions in this country. Prevalence and predictive factors for hepatotoxicity were determined.

Results

Data on 1024 patients (median age 23 years, 82.0% female, ethnic groups: Malays 40.8%, Chinese 20.9% , Indian 33.2%) were obtained from January 2005 to December 2009. The median amount of paracetamol ingestion was 10.0 (IQR 5.0 - 15.0) g and the median serum paracetamol level was 274.80 (IQR 70.0 - 640.0) μmol/L at presentation. 75 (7.3%) patients developed hepatotoxicity. 23/ 55 (41.8%) patients who had ingested > 10 g of paracetamol and had a delayed (> 24 hour) administration of N-acetyl cystine (NAC) developed hepatotoxicity. No patients developed acute liver failure nor suffered any mortality (0%). Independent predictors for hepatotoxicity were identified as Malay (OR 2.22, 95% CI = 1.13-4.37) and Chinese (OR 3.26, 95% CI = 1.55-6.84) ethnicity, paracetamol dose > 10 g (OR 2.61, 95% CI = 1.53-4.46), prolonged duration of time from paracetamol ingestion to hospital presentation (> 24 hours OR 10.71, 95% CI = 3.46-33.15) and prolonged duration of time from paracetamol ingestion to NAC administration (> 24 hours OR 9.02, 95% CI = 2.97-27.45).

Conclusions

Paracetamol-induced hepatotoxicity rates in a multi-ethnic Asian population was low at 7.3%. Mortality and morbidity were non-existent despite high doses of paracetamol ingestion and delayed presentations to hospital.

A cost effectiveness analysis of the preferred antidotes for acute paracetamol poisoning patients in Sri Lanka

Background

Acute paracetamol poisoning is a rapidly increasing problem in Sri Lanka. The antidotes are expensive and yet no health economic evaluation has been done on the therapy for acute paracetamol poisoning in the developing world. The aim of this study is to determine the cost effectiveness of using N-acetylcysteine over methionine in the management of acute paracetamol poisoning in Sri Lanka.

Methods

Economic analysis was applied using public healthcare system payer perspective.

Costs were obtained from a series of patients admitted to the National Hospital of Sri Lanka with a history of acute paracetamol overdose. Evidence on effectiveness was obtained from a systematic review of the literature. Death due to hepatotoxicity was used as the primary outcome of interest. Analysis and development of decision tree models was done using Tree Age Pro 2008.

Results

An affordable treatment threshold of Sri Lankan rupees 1,537,120/death prevented was set from the expected years of productive life gained and the average contribution to GDP. A cost-minimisation analysis was appropriate for patients presenting within 10 hours and methionine was the least costly antidote. For patients presenting 10-24 hours after poisoning, n-acetylcysteine was more effective and the incremental cost effectiveness ratio of Sri Lankan rupees 316,182/life saved was well under the threshold. One-way and multi-way sensitivity analysis also supported methionine for patients treated within 10 hours and n-acetylcysteine for patients treated within 10-24 hours as preferred antidotes.

Conclusions

Post ingestion time is an important determinant of preferred antidotal therapy for acute paracetamol poisoning patients in Sri Lanka. Using n-acetylcysteine in all patients is not cost effective. On economic grounds, methionine should become the preferred antidote for Sri Lankan patients treated within 10 hours of the acute ingestion and n-acetylcysteine should continue to be given to patients treated within 10-24 hours.

Age-related changes in the hepatic pharmacology and toxicology of paracetamol

Optimal pharmacotherapy is determined when the pharmacokinetics and pharmacodynamics of the drug are understood. However, the age-related changes in pharmacokinetics and pharmacodynamics, as well as the increased interindividual variation mean optimal dose selection are a challenge for prescribing in older adults. Poor understanding of how hepatic clearance and toxicity are different with age results in suboptimal dose selection, poor efficacy, and/or increased toxicity. Of particular concern is the analgesic paracetamol which has been in use for more than 50 years and is consumed by a large proportion of older adults. Paracetamol is considered to be a relatively safe drug; however, caution must be taken because of its potential for toxicity. Paracetamol-induced liver injury from accidental overdose accounts for up to 55% of cases in older adults. Better understanding of how age affects the hepatic clearance and toxicity of drugs will contribute to evidence-based prescribing for older people, leading to fewer adverse drug reactions without loss of benefit.

Relationship between serum acetaminophen concentration and N-acetylcysteine-induced adverse drug reactions

Intravenous N-acetylcysteine is usually regarded as a safe antidote. However, during the infusion of the loading dose, different types of adverse drug reactions (ADR) may occur. The objective of this study was to investigate the relation between the incidence of different types of ADR and serum acetaminophen concentration in patients presenting to the hospital with acetaminophen overdose. This is a retrospective study of patients admitted to the hospital for acute acetaminophen overdose over a period of 5 years (1 January 2004 to 31 December 2008). Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. SPSS 15 was used for data analysis. Of 305 patients with acetaminophen overdose, 146 (47.9%) were treated with intravenous N-acetylcysteine and 139 (45.6%) were included in this study. Different types of ADR were observed in 94 (67.6%) patients. Low serum acetaminophen concentrations were significantly associated with cutaneous anaphylactoid reactions but not other types of ADR. Low serum acetaminophen concentration was significantly associated with flushing (p < 0.001), rash (p < 0.001) and pruritus (p < 0.001). However, there were no significant differences in serum acetaminophen concentrations between patients with and without the following ADR: gastrointestinal reactions (p = 0.77), respiratory reactions (p = 0.96), central nervous reactions (p = 0.82) and cardiovascular reactions (p = 0.37). In conclusion, low serum acetaminophen concentrations were associated with higher cutaneous anaphylactoid reactions. Such high serum acetaminophen concentrations may be protective against N-acetylcysteine-induced cutaneous ADR.

Association between gastrointestinal manifestations following acetaminophen poisoning and outcome in 291 acetaminophen poisoning patients

BACKGROUND

Acetaminophen poisoning is a common clinical problem, and early identification of patients with more severe poisoning is key to improving outcomes.

PURPOSES

This study intends to document prevalence, clinical characteristics, and predictors of gastrointestinal (GI) manifestations and to assess the impact of these manifestations on outcome in patients with acetaminophen poisoning.

METHODS

This is a retrospective cohort study of hospital admissions for acute acetaminophen poisoning conducted over a period of 5 years from 1 January 2004 to 31 December 2008. Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. Statistical Package for Social Sciences (SPSS) 15 was used for data analysis.

RESULTS

Two hundred and ninety-one patients were studied; their mean age was 23.01 +/- 7.4 years and 76.6% had GI manifestations. Multiple logistic regression showed that significant risk factors for GI manifestations were present among patients who reported acetaminophen dose ingested >or=10 g (p < 0.001), and latency time more than 8 hours (p = 0.030). GI manifestations at first admission predicted poorer outcomes in terms of estimated acetaminophen levels to be a possible toxic (p < 0.001), elevated bilirubin levels (p = 0.002), prolonged prothrombin time (PT; p = 0.002), elevated creatinine level (p = 0.028), declination of potassium level (p < 0.001), and prolonged hospital stay (p < 0.001).

CONCLUSIONS

GI manifestations were common among patients with acetaminophen poisoning. This study suggests that the presence of GI manifestations at first presentation appears to be an important risk marker of subsequent hepatotoxicity and nephrotoxicity.

Incidence of adverse drug reactions induced by N-acetylcysteine in patients with acetaminophen overdose

BACKGROUND

Intravenous N-acetylcysteine (IV-NAC) is widely recognized as the antidote of choice for acetaminophen overdose. However, its use is not without adverse drug reactions (ADR) that might affect therapeutic outcome or lead to treatment delay.

OBJECTIVE

The aim of this study was to investigate the type and incidence of ADR induced by IV-NAC in patients treated for acetaminophen overdose.

METHODS

This is a retrospective study of patients admitted to the hospital for acute acetaminophen overdose over a period of 4 years (1 January 2005 to 31 December 2008). The primary outcome of interest in this study was the occurrence of ADR during NAC administration. Pearson chi-square test or Fisher's exact test, student's t test, and Mann-Whitney U test were used in univariate analysis. SPSS 15 was used for data analysis.

RESULTS

Two hundred and fifty five patients were studied. Different types of ADR were observed in 119 (46.7%) cases. Of those patients, 83 (69.7%) had been treated with IV-NAC versus 36 (30.3%) who had not (p < .001). The following ADR were significantly associated with IV-NAC administration: vomiting (p = .001), flushing (p < .001), rash (p < .001), pruritus (p < .001), chest pain (p = .001), bronchospasm (p = .03), coughing (p = .01), headache (p = .001), dizziness (p < .001), convulsion (p = .03), and hypotension (p = .001). ADR were mild in 54 (43.2%), moderate in 17 (13.6%), and severe in 12 (9.6%) patients. There were no ADR in 42 (33.6%) patients. Comparative results of the characteristics of patients who reacted to IV-NAC and nonreactors showed that patients with ADR had no significant difference in age, gender, ethnicity, amount ingested, latency time, and acetaminophen level than nonreactors.

CONCLUSION

ADR to IV-NAC were common among patients with acetaminophen overdose, but mostly minor and all reported adverse reactions were easily managed.

Adverse reactions associated with acetylcysteine

INTRODUCTION

Paracetamol (acetaminophen) is one of the most common agents deliberately ingested in self-poisoning episodes and a leading cause of acute liver failure in the western world. Acetylcysteine is widely acknowledged as the antidote of choice for paracetamol poisoning, but its use is not without risk. Adverse reactions, often leading to treatment delay, are frequently associated with both intravenous and oral acetylcysteine and are a common source of concern among treating physicians.

METHODS

A systematic literature review investigating the incidence, clinical features, and mechanisms of adverse effects associated with acetylcysteine.

RESULTS

A variety of adverse reactions to acetylcysteine have been described ranging from nausea to death, most of the latter due to incorrect dosing. The pattern of reactions differs with oral and intravenous dosing, but reported frequency is at least as high with oral as intravenous. The reactions to the intravenous preparation result in similar clinical features to true anaphylaxis, including rash, pruritus, angioedema, bronchospasm, and rarely hypotension, but are caused by nonimmunological mechanisms. The precise nature of this reaction remains unclear. Histamine now seems to be an important mediator of the response, and there is evidence of variability in patient susceptibility, with females, and those with a history of asthma or atopy are particularly susceptible. Quantity of paracetamol ingestion, measured through serum paracetamol concentration, is also important as higher paracetamol concentrations protect patients against anaphylactoid effects. Most anaphylactoid reactions occur at the start of acetylcysteine treatment when concentrations are highest. Acetylcysteine also affects clotting factor activity, and this affects the interpretation of minor disturbances in the International Normalized Ratio in the context of paracetamol overdose.

CONCLUSION

This review discusses the incidence, clinical features, underlying pathophysiological mechanisms, and treatment of adverse reactions to acetylcysteine and identifies particular "at-risk" patient groups. Given the commonality of adverse reactions associated with acetylcysteine, it is important to ensure that any adverse event does not preclude patients from receiving maximal hepatic protection, particularly in the context of significant paracetamol ingestion. Further work on mechanisms should allow specific therapies to be developed.

Safety and efficacy of intravenous N-acetylcysteine for acetaminophen overdose: analysis of the Hunter Area Toxicology Service (HATS) database

BACKGROUND

Acetaminophen (N-acetyl-p-aminophenyl; APAP) is the leading drug used in self-poisoning and frequently causes hepatotoxicity, including acute liver failure.

OBJECTIVE

To provide descriptive data on the safety and efficacy of intravenous N-acetylcysteine (IV-NAC) in the treatment of APAP toxicity, based on information in the Hunter Area Toxicology Service (HATS) database involving residents of the Greater Newcastle Area of New South Wales, Australia.

METHODS

This was a retrospective analysis of all APAP overdoses from January 1987 to January 2003. Data were collected prospectively according to a published protocol and included patient characteristics, exposures to APAP and other potential toxins, treatments, and outcomes. Primary safety/tolerability endpoints included the mortality rate and incidence of adverse drug reactions, while efficacy endpoints included alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels.

RESULTS

Of 1749 patients, 399 (22.8%) were treated with IV-NAC. Of these, 37 (9.3%) had an adverse drug reaction to IV-NAC, of which seven (1.8% of total) were anaphylactoid. There were five deaths in hospital (mortality rate = 0.3%), including two attributed to APAP (0.1%) and none to IV-NAC. Of 64 patients who were treated with IV-NAC within 8 hours after APAP ingestion and had available ALT/AST data, two (3.1%) developed hepatotoxicity (AST/ALT > 1000 IU/L) compared with 32 (25%) of 128 patients receiving IV-NAC > 8 hours after APAP ingestion (p = 0.0002). A total of 26 patients (15.6%) receiving IV-NAC treatment within 8 hours after APAP ingestion had hospitalization stays > 48 hours compared with 70 (33.3%) receiving IV-NAC > 8 hours after ingestion (p < 0.0001).

CONCLUSIONS

For patients with APAP overdose seen in the HATS database of New South Wales, Australia, in-hospital death was infrequent (< 1%) and hepatotoxicity was significantly less likely when IV-NAC was administered within 8 hours after APAP ingestion compared with longer intervals (p < 0.01). As a descriptive retrospective database analysis, this study could not exclude certain sources of bias, including temporal changes over the 16-year course of data collection in the use of IV-NAC and low ascertainment of mild, self-limiting reactions to IV-NAC.

Acetaminophen hepatotoxicity

Acetaminophen is a commonly used antipyretic and analgesic agent. It is safe when taken at therapeutic doses; however, overdose can lead to serious and even fatal hepatotoxicity. The initial metabolic and biochemical events leading to toxicity have been well described, but the precise mechanism of cell injury and death is unknown. Prompt recognition of overdose, aggressive management, and administration of N-acetylcysteine can minimize hepatotoxicity and prevent liver failure and death. Liver transplantation can be lifesaving for those who develop acute liver failure.

Interventions for paracetamol (acetaminophen) overdose

BACKGROUND

Poisoning with paracetamol (acetaminophen) is a common cause of hepatotoxicity in the Western World. Inhibition of absorption, removal from the vascular system, antidotes, and liver transplantation are interventions for paracetamol poisoning.

OBJECTIVES

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

SEARCH STRATEGY

We identified trials through electronic databases, manual searches of bibliographies and journals, authors of trials, and pharmaceutical companies until December 2005.

SELECTION CRITERIA

Randomised clinical trials and observational studies were included.

DATA COLLECTION AND ANALYSIS

The primary outcome measure was all-cause mortality plus liver transplantation. Secondary outcome measures were clinical symptoms, (eg, hepatic encephalopathy, fulminant hepatic failure), hepatotoxicity, adverse events, and plasma paracetamol concentration. We used Peto odds ratios and odds ratios with 95% confidence intervals (CI) for analysis of outcomes. Random- and fixed-effects meta-analyses were performed.

MAIN RESULTS

Ten small and low-methodological quality randomised trials, one quasi-randomised study, and 48 observational studies were identified. It was not possible to perform relevant meta-analyses of randomised trials that have addressed our outcome measures. Activated charcoal, gastric lavage, and ipecacuanha are able to reduce the absorption of paracetamol, but the clinical benefit is unclear. Of these, activated charcoal seems to have the best risk-benefit ratio. N-acetylcysteine seems preferable to placebo/supportive treatment, dimercaprol, and cysteamine, but N-acetylcysteine's superiority to methionine is unproven. It is not clear which N-acetylcysteine treatment protocol offers the best efficacy. No strong evidence supports other interventions for paracetamol overdose. N-acetylcysteine may reduce mortality in patients with fulminant hepatic failure (Peto OR 0.26, 95% CI 0.09 to 0.94, one trial). Liver transplantation has the potential to be life saving in fulminant hepatic failure, but refinement of selection criteria for transplantation and long-term outcome reporting are required.

AUTHORS' CONCLUSIONS

Our results highlight a paucity of randomised trials on interventions for paracetamol overdose. Activated charcoal seems the best choice to reduce absorption. N-acetylcysteine should be given to patients with overdose but the selection criteria are not clear. No N-acetylcysteine regime has been shown to be more effective than any other. It is a delicate balance when to proceed to liver transplantation, which may be life-saving for patients with poor prognosis.