Deaths from low dose paracetamol poisoning

Evaluation of cut-off values in acute paracetamol overdose following the United Kingdom guidelines

Background

The United Kingdom guideline for acute paracetamol overdose has recommended the use of ‘100-treatment line’. Emergency medical centers in some developing countries lack the resources for timely reporting of paracetamol concentrations, hence treatment depends on reported dose. This study aimed to examine whether using an reported dose is safe to predict concentration above the 100-line.

Methods

Data were retrieved from two emergency medical centers retrospectively, between 2010 and 2017. The inclusion criteria were single acute paracetamol overdose, presentation within 15 h, and age ≥ 14 years. Multiple linear regression was performed to determine the effect of ingested dose on paracetamol concentration. Subgroups were created based on ingested dose, rate of concentration above 100-line were investigated.

Results

One hundred and seventy-two patients were enrolled in the primary analysis; median dose was 133.3 mg/kg and 46 (37.8%) had concentration above 100-line in the first test. Only dose per weight was moderately correlated with the first concentration (R² = 0.410, p < 0.001). In the ≤200 mg/kg ingestion group, 18 patients showed concentration above 100-line and 8 showed acute liver injury. The cut-off value of 150 mg/kg showed 82.6% sensitivity and 73.8% specificity to predict concentration above 100-line.

Conclusion

Where paracetamol concentration is not available and activated charcoal is readily used, following United Kingdom guideline, it is safe to use an ingested dose of > 150 mg/kg as the cut-off value for N-acetylcysteine treatment with risk stratification for hepatotoxicity if the patient is ≥14 years and visit the ED within 15 h after an acute paracetamol overdose.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-021-00547-1.

[Drug interactions in pain therapy]

BACKGROUND

Pain is one of the most common reasons for consulting a physician. Chronic pain patients often suffer from a variety of comorbidities, such as depression and anxiety and they are therefore often simultaneously treated with more than one drug. The probability of drug interactions increases with every additional drug.

MATERIAL AND METHODS

A systematic internet and literature search up to February 2015 was carried out. Systematic lists were included. In addition, the drug prescription information sheets were used and an internet search via Pubmed and google.com was carried out for drugs alone and in combination in order to find substance-specific interactions.

RESULTS

A differentiation is made between pharmaceutical, pharmacodynamic and pharmacokinetic drug interactions. Pharmaceutical interactions are caused by chemical, physical or physicochemical incompatibility of drugs or adjuvants used. These can even occur outside the body and during concomitant administration via the same route. A pharmacodynamic interaction in pain management is for example the additive sedative effect of opioids and benzodiazepines when taken together. Pharmacokinetic interactions occur during the absorption, distribution, metabolism and in the elimination phases.

CONCLUSION

Many drug interactions can be avoided by careful and continuous evaluation of pharmacotherapy and if necessary its adaptation; however, a sound knowledge of the underlying pharmacological mechanisms and the properties of currently used analgesics is necessary.

Treating acetaminophen overdose: thresholds, costs and uncertainties

The United Kingdom's Medicines and Healthcare Products Regulatory Agency (MHRA) modified the indications for N-acetylcysteine therapy of acetaminophen (paracetamol) overdose in September 2012. The new treatment threshold line was lowered to 100 mg/L (662 μmol/L) for a 4 hours acetaminophen concentration from the previous 200 mg/L (1325 μmol/L). This decision has the potential to substantially increase overall costs associated with acetaminophen overdose with unclear benefits from a marginal increase in patients protected from hepatotoxicity, fulminant hepatic failure, death, or transplant. Changing the treatment threshold for acetaminophen overdose also implies that ingestion amounts previously thought not to require acetaminophen concentration measurements would need to be revised. As a result, more individuals will be sent to hospitals in order that everyone with a predicted 4 hours concentration above the 100 mg/L line will have concentrations measured and potentially be treated with N-acetylcysteine. Before others consider adopting this new treatment guideline, formal cost-effectiveness analyses need to be performed to define the appropriate thresholds for referral and treatment.

Acetaminophen and acetylcysteine dose and duration: past, present and future

Acetylcysteine has been utilized successfully in the treatment of acetaminophen overdose since the 1970s. Although prospective trials as to efficacy and safety of acetylcysteine were conducted, there were no randomized controlled trials. This commentary addresses the reasons for this, and the background to choice of dose of acetylcysteine utilized in the oral and IV dosing regimens. Nomograms to predict possible hepatotoxicity based upon time of ingestion of acetaminophen were developed from a relatively arbitrary definition of toxicity as an aspartate aminotransferase/alanine aminotransferase (ALT/AST) greater than 1000 IU/L. While these have proved generally useful, patients still continue to develop hepatic damage after acetaminophen overdose, particularly if they present late after ingestion. The optimum management of these patients remains unclear, and one area of uncertainty is the dose and duration of acetylcysteine in various circumstances. This article discusses the issues that need to be elucidated to better target changes in acetylcysteine dose. The potential for measurements of other markers to improve treatment selection is the subject of further research.

A Three-Stage-Integrative Approach for the Identification of Potential Hepatotoxic Compounds From Botanical Products

With the increasing use of herbal medicines and dietary supplements, intensive concerns about their potential toxicities have been raised. Screening and identifying the toxic compounds from these botanical products composed by hundreds of components have become a critical but challenging problem. In this study, 3 methods, including fraction separation, an in-house-developed fluorescein diacetate-based automatic microscopy screening (FAMS) platform, and liquid chromatography-mass spectrometry-based compounds identification were integrated within the Three-Stage-Integrative (TSI) approach for the identification of potential hepatotoxicants from botanical products. The sensitivity and linear range of FAMS assay was validated and compared with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay by previously reported hepatotoxic compounds. The success of TSI approach was further demonstrated by its application to Fructus aristolochiae. Aristolochic acid IVa and aristolodione were tentatively identified to be potential hepatotoxicants in this plant. These applications suggested that our TSI approach provides an effective tool for identifying potential toxic compounds from botanical products.

Paracetamol metabolism and related genetic differences

Paracetamol (acetaminophen) is a worldwide used analgesic and antipyretic drug. It is metabolised via several metabolic pathways, including glucuronidation, sulfation, oxidation, hydroxylation, and deacetylation: Hepatic and other organ damage may occur, especially in overdose, because of the accumulation of a toxic metabolite. Intersubject and ethnic differences have been reported in paracetamol metabolism activation, suggesting possible differences in susceptibility to toxicity and in pain alleviation, linked to different pharmacogenetic profiles. This article aims at reviewing, in the literature, the links between paracetamol metabolism and enzyme genotypes in the context of toxic side effects and efficacy of paracetamol in therapeutics.

Drugs and pharmaceuticals: management of intoxication and antidotes

The treatment of patients poisoned with drugs and pharmaceuticals can be quite challenging. Diverse exposure circumstances, varied clinical presentations, unique patient-specific factors, and inconsistent diagnostic and therapeutic infrastructure support, coupled with relatively few definitive antidotes, may complicate evaluation and management. The historical approach to poisoned patients (patient arousal, toxin elimination, and toxin identification) has given way to rigorous attention to the fundamental aspects of basic life support--airway management, oxygenation and ventilation, circulatory competence, thermoregulation, and substrate availability. Selected patients may benefit from methods to alter toxin pharmacokinetics to minimize systemic, target organ, or tissue compartment exposure (either by decreasing absorption or increasing elimination). These may include syrup of ipecac, orogastric lavage, activated single- or multi-dose charcoal, whole bowel irrigation, endoscopy and surgery, urinary alkalinization, saline diuresis, or extracorporeal methods (hemodialysis, charcoal hemoperfusion, continuous venovenous hemofiltration, and exchange transfusion). Pharmaceutical adjuncts and antidotes may be useful in toxicant-induced hyperthermias. In the context of analgesic, anti-inflammatory, anticholinergic, anticonvulsant, antihyperglycemic, antimicrobial, antineoplastic, cardiovascular, opioid, or sedative-hypnotic agents overdose, N-acetylcysteine, physostigmine, L-carnitine, dextrose, octreotide, pyridoxine, dexrazoxane, leucovorin, glucarpidase, atropine, calcium, digoxin-specific antibody fragments, glucagon, high-dose insulin euglycemia therapy, lipid emulsion, magnesium, sodium bicarbonate, naloxone, and flumazenil are specifically reviewed. In summary, patients generally benefit from aggressive support of vital functions, careful history and physical examination, specific laboratory analyses, a thoughtful consideration of the risks and benefits of decontamination and enhanced elimination, and the use of specific antidotes where warranted. Data supporting antidotes effectiveness vary considerably. Clinicians are encouraged to utilize consultation with regional poison centers or those with toxicology training to assist with diagnosis, management, and administration of antidotes, particularly in unfamiliar cases.

Guidelines for the management of paracetamol poisoning in Australia and New Zealand--explanation and elaboration. A consensus statement from clinical toxicologists consulting to the Australasian poisons information centres

Paracetamol is involved in a large proportion of accidental paediatric exposures and deliberate self-poisoning cases, although subsequent hepatic failure and death are both uncommon outcomes. The optimal management of most patients with paracetamol overdose is usually straightforward. However, several differing nomograms and varying recommendations regarding potential risk factors for hepatic injury introduce complexity. In order to reconcile management advice with current Australasian clinical toxicology practice, revised guidelines have been developed by a panel of clinical toxicologists consulting to the poisons information centres in Australia and New Zealand using a workshop and consultative process. This article summarises the rationale for the recommendations made in these new guidelines.

Antipyretic analgesics: nonsteroidal antiinflammatory drugs, selective COX-2 inhibitors, paracetamol and pyrazolinones

Antipyretic analgesics are a group of heterogeneous substances including acidic (nonsteroidal antiinflammatory drugs, NSAIDs) and nonacidic (paracetamol, pyrazolinones) drugs. Moreover, various selective cyclooxygenase-2 (COX-2) inhibitors with improved gastrointestinal tolerability as compared with conventional NSAIDs have been established for symptomatic pain treatment in recent years. The present review summarizes the pharmacology of all of these drugs with particular emphasis on their rational use based on the diverse pharmacokinetic characteristics and adverse drug reaction profiles. Referring to the current debate, potential mechanisms underlying cardiovascular side effects associated with long-term use of COX inhibitors are discussed.

Effects of Combined UDP-Glucuronosyltransferase (UGT) 1A1*28 and 1A6*2 on Paracetamol Pharmacokinetics in β-Thalassemia/HbE

In addition to pathophysiological changes, genetic variations can alter drug pharmacokinetics in patients with thalassemia. Numerous drugs are metabolized by UDP-glucuronosyltransferases (UGT) including paracetamol (PCM), a widely used analgesic. Co-occurrence of the UGT1A1 polymorphism (UGT1A1*28) and the UGT1A6 polymorphism (UGT1A6*2) may affect PCM glucuronidation. To elucidate the effect of these combined polymorphisms on the PCM metabolism in thalassemic patients, 15 beta-thalassemia/hemoglobin E subjects with three different UGT1A genotypes received a single oral dose of 1,000 mg PCM. Drug disposition was determined by HPLC. Patients who have UGT1A6*2 without UGT1A1*28 showed a significant, lower area under concentration-time curve (AUC(0)-->infinity) of PCM, PCM-glucuronide and PCM-sulfate than those of the patients with wild-type UGT1A1 and UGT1A6 (p < 0.05). In addition, a high elimination rate constant and clearance of PCM and its metabolites were also found in these patients (p < 0.05). Ourstudy suggests that a subtherapeutic level of PCM may occur in patients who have UGT1A6*2 without UGT1A1*28.

A pharmacokinetic study of paracetamol in Thai β-thalassemia/HbE patients

BACKGROUND

Thalassemia may alter the pharmacokinetics of several drugs in thalassemic patients. Paracetamol is a commonly used analgesic and antipyretic drug which is extensively metabolized in the liver via glucuronidation. The aim of this study was to compare the pharmacokinetics of paracetamol (PCM) and its metabolites [paracetamol glucuronide (PCM-G), paracetamol sulfate (PCM-S), and paracetamol cysteine (PCM-C)] in 16 patients with 16 normal subjects.

METHOD

Following an overnight fast, a single dose of paracetamol (1,000 mg of Tylenol(R)) was given and blood samples were obtained at predose, 0.5, 1, 1.5, 2, 3, 4, 5, 7, and 9 h after dosing for determination of the plasma levels of PCM and its metabolites by high-performance liquid chromatography.

RESULTS

There was no significant difference in maximum concentration of PCM between groups. However, a significantly shorter elimination half-life of PCM was observed in the thalassemic subjects (p<0.001). Total apparent clearance of PCM was significantly faster in thalassemic subjects (p<0.01) while the apparent volume of distribution of PCM did not change. The area under the concentration time curve (AUC(0->infinity)) of PCM-G and PCM-S increased in thalassemic subjects (p<0.05) whereas this parameter for PCM-C was slightly lower in the patients. The half-lives of PCM metabolites were significantly shorter (p<0.01) in thalassemic subjects.

CONCLUSION

The results indicate that the elimination of PCM and its metabolites in thalassemic subjects is faster than that in normal subjects. Our pharmacokinetic data provide additional evidence that plasma PCM-G is higher in thalassemic patients with hyperbilirubinemia, which could be a casual relationship in regulating the UDP-glucuronosyltransferase expression.

The hospital management of fatal self-poisoning in industrialized countries: an opportunity for suicide prevention?

Suicide by self-poisoning is a prevalent cause of death worldwide. A substantial proportion of individuals who poison themselves come into contact with medical services before they die. Our focus in the current study was the medical management of drug self-poisoning in industrialized countries and its possible contribution to suicide prevention. We reviewed the literature to determine the proportion of self-poisoning suicides who reach hospital alive, the sociodemographic and clinical characteristics of in-hospital overdose deaths, the in-hospital management this group of patients receives, and whether there are specific aspects of pre-hospital care and in-hospital management that have the potential to improve survival. Between 11% and 28% of individuals who died following deliberate ingestion of drugs reached hospital alive. The substances which were most frequently implicated in death were paracetamol (acetaminophen) and paracetamol compounds, tricyclic antidepressants, and benzodiazepines. Most patients received fairly intensive treatment, yet death may have been preventable in a small proportion of cases. Only one intervention (the administration of acetylcysteine) was shown to reduce mortality and this was in a highly selected group of patients (those who had ingested paracetamol and developed fulminant hepatic failure). It is possible that other interventions such as better airway management, the prompt administration of activated charcoal, and improved pre-hospital care may improve outcomes but their potential contribution to suicide prevention needs to be investigated in future studies.

Potentially Fatal Paracetamol Overdose and Successful Treatment with 3 Days of Intravenous N-acetylcysteine Regime – A Case Report

Introduction: Paracetamol overdose is the most common drug overdose worldwide. To our knowledge, the maximum number of paracetamol tablets ingested reported in the literature is 45 g. Clinical Picture: We describe a 21-year-old patient who acutely ingested 120 tablets, each 500 mg paracetamol (i.e., 60 g equivalent to 1200 mg/kg body weight) in a suicidal attempt. Our patient also drank 2 bottles of codeine-based cough syrup equivalent to 360 mg of codeine. At 6 hours post ingestion, her serum paracetamol level was 207 mg/L. The poor prognostic factors for paracetamol overdose in our patient included massive paracetamol ingestion (confirmed by blood levels), codeine co-ingestion and elevated serum amylase (189 U/L). Treatment: She was treated with a 3-day modified regimen of intravenous N-acetylcysteine. Outcome: The liver function tests and the prothrombin time remained normal over the second and third day of admission and the patient was discharged without complications on the fifth day. Conclusion: From this experience we feel that in very severe paracetamol poisoning, a modified regime of intravenous N- acetylcysteine for 3 days is safe and efficacious. Key words: Codeine, Hyperamylasaemia, Ingestion, Suicidal

A Risk Quantification Instrument for Acute Acetaminophen Overdose Patients Treated With N-Acetylcysteine

STUDY OBJECTIVE

The risk of hepatotoxicity after acute acetaminophen overdose varies with timed serum acetaminophen concentration and delay to treatment. The ability to accurately predict hepatotoxicity is needed to reduce confusion about the optimal treatment regimen for individual patients and the effects of risk modifiers such as ethanol. We quantitatively estimate the risk of hepatotoxicity based on the degree and duration of pretreatment exposure to supratherapeutic concentrations of acetaminophen.

METHODS

We examined all hospitalizations for acute acetaminophen overdose within a retrospective multicenter Canadian registry. We used a previously developed composite measure incorporating timed serum acetaminophen concentration and time to N-acetylcysteine treatment into a single parameter. We then modeled hepatotoxicity on this parameter, as well as age, sex, and ethanol use. Hepatotoxicity was defined as peak aminotransferase level of 1,000 IU/L or greater at 24 hours or longer.

RESULTS

Of 1,270 admitted patients treated mostly with intravenous N-acetylcysteine for less than 24 hours, our model accurately identified the 94 patients who developed hepatotoxicity (discriminatory index 0.93). Hepatotoxicity occurred in none of the 313 patients (95% confidence interval [CI] 0% to 1.0%) above the traditional 150 mug/mL treatment line who were classified as low risk (<1%) using our instrument. After adjustment for severity of exposure, the risk of hepatotoxicity was considerably higher in the absence of coingested ethanol (median hepatotoxic dose 16.5 mmol/L x hour [95% CI 8.74 to 31.0 mmol/L x hour] versus 27.1 mmol/L x hour [95% CI 11.1 to 66.3 mmol/L x hour]), particularly among alcoholics (4.79 mmol/L x hour [95% CI 2.13 to 10.8 mmol/L x hour]).

CONCLUSION

Our risk prediction instrument identifies a large group of low-risk patients for whom 20-hour intravenous N-acetylcysteine therapy is sufficient. Our results suggest that acute and chronic ethanol use dramatically influences acetaminophen toxicity. This work may facilitate the evaluation of individualized treatment strategies for higher-risk patients.

Self-poisoning suicides in England: a multicentre study

BACKGROUND

Suicide by self-poisoning is an important cause of death worldwide. A substantial proportion of those with a fatal outcome may come into contact with medical services before they die.

AIM

To estimate the proportion of self-poisoning suicides who reached hospital alive; to compare those who reached hospital alive with those who did not; to describe in detail the clinical characteristics and medical management of those dying in hospital.

DESIGN

Retrospective audit.

METHODS

We studied 24 coroners' jurisdictions across England, reviewing coroners' files and identifying all suicides by self-poisoning (drugs and other ingestible poisons) from 1 January 2001 to 31 December 2001.

RESULTS

Of the 214 individuals who completed suicide by self-poisoning during the study period, 49 (23%) reached hospital alive. Those reaching hospital were more likely to be female, more likely to have ingested paracetamol and less likely to have ingested co-proxamol. In the hospital sample, the commonest causes of death were respiratory (n = 10), hepatic or hepatorenal (n = 8), cardiac (n = 5), or a result of hypoxic brain injury (n = 5). Only 18% of in-hospital deaths occurred within 24 h of the overdose.

DISCUSSION

Extrapolating to England as a whole, we might expect 300 self-poisoning suicides per year to reach hospital alive (6% of all suicides). Improved medical management might produce a small but significant reduction in the rate of suicide. Such interventions should not be restricted to the emergency care domain. Further research will help to clarify the likely contribution of improved medical management to suicide prevention.

Liver delivery of NO by NCX-1000 protects against acute liver failure and mitochondrial dysfunction induced by APAP in mice

1. NCX-1000, (3alpha, 5beta, 7beta)-3,7-dihydroxycholan-24oic acid[2-methoxy-4-[3-[4-(nitroxy)butoxy]-3-oxo-1-propenyl]phenyl ester, is a nitric oxide (NO)-derivative of ursodeoxyxholic acid (UDCA) that selectively release NO in the liver. 2. Here, we demonstrated that administering mice with 40 micromol kg(-1) NCX-1000, but not UDCA, improves liver histopathology and reduces mortality caused by 330 micromol kg(-1) APAP from 60 to 25% (P<0.01). Administration of NCX-1000, in a therapeutic manner, that is, 2 h after acetaminophen (APAP) intoxication reduced mortality, improved liver histopathology and prevented liver IFN-gamma, TNF-alpha, Fas/Fas ligand and inducible nitric oxide synthase (iNOS) mRNA accumulation caused by APAP. 3. In vitro exposure of primary cultures of mouse hepatocytes to APAP, 6.6 mm, resulted in apoptosis followed by necrosis. Loss of cell viability correlates with early mitochondrial membrane potential (Deltapsi(m)) hyperpolarization followed by depolarization and cytochrome c translocation from mitochondria to cytosol. APAP-induced apoptosis associated with procaspase-3 and -9 cleavage, appearance of truncated Bid and activation of poly(ADP-ribose) polymerase (PARP). 4. Treating primary culture of hepatocytes with 5 microm cyclosporine and 10 microm trifluoperazine for eight resulted in significant reduction of apoptosis induced by APAP suggesting that loss of Deltapsim was mechanistically involved in apoptosis induced by APAP in vitro. 5. NCX-1000, but not UDCA, concentration-dependently (ED(50)=16 microm) protected against Deltapsi(m) depolarization and reduced transition from apoptosis to necrosis caused by 6.6 mm APAP. 6. Treating primary cultures of hepatocytes with the NO-donor DETA-NO, 100 microm, reduced apoptosis induced by APAP and prevented caspase activation. 7. In conclusion, NCX-1000 is effective in protecting against APAP-induced hepatotoxicity when administered in a therapeutic manner. This protection may involve the inhibition of apoptosis and the maintenance of mitochondrial integrity.

[The flavonoids effect against vinblastine, cyclophosphamide and paracetamol toxicity by inhibition of lipid-peroxydation and increasing liver glutathione concentration]

The paracetamol and cyclophosphamid are metabolized in the liver by the cytochrome P450. The formed reactive intermediates are responsible of a hepatocyte depletion of the glutathion and a lipoperoxydation. the vinblastine is also a chemotherapeutic agent hepatotoxic and hematotoxic. Otherwise, flavonoïds are polyphenols substances of plant origin having some biological and anti-oxydative properties. However no information is available on their effects on glutathion and glutathion-s-transferases. In our research, we valued the effect of oral administration of flavonoids (diosmine and quercetine) under shape of propolis extract to 60 mg/kg daily during 14 days, on hematological and hepatic toxicity of a single dose of cyclophosphamide 80 mg/kg by intravenous way, vinblastine 2 mg/kg by intravenous way and the hepatic toxicity of the paracetamol managed by oral way to 200 mg/kg corresponding to 2/3 the DL50 at the rat female albinos wistar. We did a blood numeration, an assessment of serum activities of transaminases and alkali phosphatases as well as quantification of the glutathion and the malondialdehyde (MDA) in liver homogenats of rats treated. Analyses are done at regular intervals; 1, 3, 7 and 14 days after the administration of drugs. In the group of rats treated by the cyclophosphamid paracetamol alone we observed since the 1st day, an increase of lipid peroxide (MDA) of 120% and a downfall of hepatic glutathion including the group receiving the vinblastine (until 210% of reduction). In the same way a severe leucopenia and a thrombopenia (70% of reduction) are observed between the 3rd and the 14th day at rats treated by the chemotherapeutic agents alone (cyclophosphamide and vinblastine). The combination of flavonoids with drugs have clearly reduced the effect of drugs toxicity. Indeed, the aplasic observed with the vinblastine, as well as the leucopenia and thrombopenia of the cyclophosphamide are corrected entirely. In the same way, we noted a restoration of rates of peroxide and glutathion. Flavonoïds seem to act by activation of the turn over of the glutathion and enzymes stimulating particularly glutathion-s-transferases permitting the captation of the reactive metabolites of the studied drugs.

Paracetamol poisoning: Which nomogram should we use?

OBJECTIVES

To determine the type of paracetamol nomograms used in Australasian EDs. To review the literature to determine the evidence base for existing nomograms.

METHODS

A cross sectional descriptive study via postal survey of all Australasian EDs accredited for specialist emergency medicine training by the Australasian College for Emergency Medicine (ACEM). A literature review using Knowledge Finder search engine was employed.

RESULTS

The response rate was 87%. The most commonly used nomogram had a four-hour treatment level of 1300 mumol/L (69%). A total of 22% of respondents used a four-hour treatment level of 1000 mumol/L. Two departments (3%) treated all patients above the 660 mumol/L line. Eleven departments (15%) did not have a treatment line below 1300 mumol/L.

CONCLUSION

Practice varies in Australasian EDs. Patients with paracetamol levels below the 1300 mumol/L have been reported in the literature to develop hepatotoxicity, and deaths have been documented. N-acetylcysteine is extremely safe when used in the recommended dosages.

Paracetamol poisoning--impact of pack size restrictions

BACKGROUND

Pack sizes of paracetamol available to the public were reduced by legislation in 1998.

OBJECTIVE

To study the effect of the legislation on paracetamol poisoning related admissions to an accident and emergency department and to a tertiary referral liver unit.

METHOD

Data were obtained from the University Hospitals, Birmingham, UK (UHB) Trust Information Service and the Queen Elizabeth Hospital liver unit records on (a) the number of patients admitted to hospital because of paracetamol overdose and (b) the number of patients admitted to the liver unit with parcetamol-induced hepatotoxicity.

RESULTS

Prior to legislation, an average of 360 people a year were admitted to UHB. However, following the change in legislation the number of admissions has fallen to an average of 250 people per year. This represents a reduction of 31%. Prior to legislation, an average of 76 people per year were admitted to the liver unit. Post-legislation this number has dropped to an average of 38 per year representing a reduction of 50%.

CONCLUSION

Legislation restricting paracetamol pack-size reduced the incidence and severity of poisoning.

Nitric oxide releasing acetaminophen (nitroacetaminophen)

The nitric oxide releasing derivative of acetaminophen (nitroacetaminophen) exhibits potent anti-inflammatory and anti-nociceptive activity in a variety of animal models. On a mol for mol basis nitroacetaminophen is some 3-20 times more potent than acetaminophen. Nitroacetaminophen exhibits little or no hepatotoxicity following administration in rat or mouse and indeed protects against the hepatotoxic activity of acetaminophen. Nitroacetaminophen does not affect blood pressure or heart rate of anaesthetised rats but has similar potency to acetaminophen as an anti-pyretic agent. The enhanced anti-inflammatory and anti-nociceptive activity of nitroacetaminophen and the reduced hepatotoxicity in these animal models is likely to be secondary to the slow release of nitric oxide from the molecule. As yet the precise molecular mechanism(s) underlying these actions of nitroacetaminophen are not clear. Evidence for inhibition of cytokine-directed formation of pro-inflammatory molecule production (e.g. COX-2, iNOS) by an effect on the NF-kappaB transduction system and/or nitrosylation (and thence inhibition) of caspase enzyme activity has been reported. Data described in this review indicate that the profile of pharmacological activity of nitroacetaminophen and acetaminophen are markedly different. The possibility that nitroacetaminophen could be an attractive alternative to acetaminophen in the clinic is discussed.

Parents' perceptions and use of analgesics at home after children's day surgery

BACKGROUND

Children are found to suffer from unnecessarily severe postoperative pain following day surgery. Reasons for parents' insufficient use of analgesics may be based on misleading perceptions of children's analgesics. The purpose of this study was to describe parents' perceptions and use of analgesics for children after discharge at home.

METHODS

In this survey, 840 questionnaires were given to parents, and answers from 201 mothers and 114 fathers whose children, aged 1-6 years, had undergone day surgery in 10 Finnish hospitals are presented.

RESULTS

One-third (36%) of the children were assessed as having moderate or severe postoperative pain after discharge. More than three-quarters of the parents had given analgesics to the child. Analgesics were given mostly to children who were assessed to have pain and found to have several types of pain behaviour. Most of the parents had accurate perceptions of children's analgesics, but some of them had misleading perceptions of the nature and adverse effects of children's analgesics, which were related to giving analgesics to the child. Fathers, more often than mothers, seem to have such misleading perceptions.

CONCLUSIONS

Parents tended to give analgesics to children who actually needed pain alleviation. Parents' perceptions of children's analgesics were mostly accurate. However, misleading perceptions of children's analgesics also exist among the parents. These misleading perceptions appear to decrease parents' use of children's postoperative pain medication.

Ease of access is a principal factor in the frequency of paracetamol overdose

BACKGROUND

In Ireland, 30% of non-fatal overdoses involve paracetamol.

AIMS

To determine how and where patients obtained paracetamol, to assess awareness of toxicity and examine the relationship between dose and suicidal intent.

METHODS

A prospective study of patients admitted following a paracetamol overdose recording their reasons for using paracetamol, their knowledge of its toxicity and their suicidal intent scale (SIS).

RESULTS

Of 100 patients, 66% obtained paracetamol in non-pharmacy outlets, 82% cited ease of availability as the reason, 55% were aware of its toxicity, 31% of liver damage and 68% did not read the warning on packets. The mean number of tablets taken was 51.3 for males and 37.2 for females (p < 0.01). Males presented later than females for medical attention (12.5 versus seven hours [p < 0.02]) and more males than females took alcohol (p < 0.03). The mean SIS score was 14.71 for males and 12.38 for females. There was a significant correlation between the SIS and the amount of paracetamol consumed (r = 0.28; p < 0.01).

CONCLUSION

The majority obtained paracetamol in local shops or at home. Knowledge of toxicity and the need for early antidote was poor. There was a significant relationship between suicidal intent and number of tablets consumed. Limiting availability could reduce number of overdoses.

Acute versus chronic alcohol consumption in acetaminophen-induced hepatotoxicity

The aim of this study was to determine by multivariate analysis how alcohol and other factors affect the clinical course and outcome in patients with acetaminophen (paracetamol) poisoning. A total of 645 consecutive patients admitted from 1994 to 2000 with single-dose acetaminophen poisoning were studied, giving special attention to alcohol history, time between overdose and intravenous N-acetylcysteine (NAC) treatment ("time to NAC"), and other data available at the time of admittance. Up until 72 hours after ingestion, time to NAC was the single most important independent risk factor. With a time to NAC less than 12 hours, the mortality rate was 0.42% (95% CI, 0.05-2.7). When time to NAC exceeded 12, 24, and 48 hours, the mortality rate increased to 6.1%, 13%, and 19%, respectively. Chronic alcohol abuse was an independent risk factor of mortality (odds ratio [OR], 3.52; 95% CI, 1.78-6.97). Acute alcohol ingestion was an independent protective factor regarding mortality in alcoholic patients (OR, 0.08; 95% CI, 0.01-0.66) but not in nonalcoholic patients (OR, 0.21; 95% CI, 0.03-1.67). Patient age and quantity of acetaminophen were independent risk factors. In conclusion, time to NAC was confirmed as the major risk factor in acetaminophen-induced hepatotoxicity and mortality. Chronic alcohol abuse was an independent risk factor that could be counteracted by concomitant acute alcohol ingestion. We suggest that patients with chronic alcoholism and suspected acetaminophen poisoning due to an increased risk of developing hepatotoxicity should be treated with NAC regardless of risk estimation.

Alcohol exposure and paracetamol-induced hepatotoxicity

Most instances of hepatotoxicity due to paracetamol in the United Kingdom and Australia are the result of large overdoses of the drug taken with suicidal or parasuicidal intent. In contrast, serious hepatotoxicity at recommended or near-recommended doses for therapeutic purposes has been reported, mainly from the United States and in association with chronic alcohol use, leading to the widely held belief that chronic alcoholics are predisposed to paracetamol-related toxicity at relatively low doses. Yet the effects of alcohol on paracetamol metabolism are complex. Studies performed in both experimental animals and humans indicate that chronic alcohol use leads to a short-term, two- to threefold increase in hepatic content of cytochrome P4502E1, the major isoform responsible for the generation of the toxic metabolite from paracetamol, although increased oxidative metabolism of paracetamol at recommended doses has not been demonstrated clinically. A reduced hepatic content of glutathione, required to detoxify the reactive metabolite, has been documented in chronic alcoholics, due probably to associated fasting and malnutrition, providing a metabolic basis for any possible predisposition of this group to hepatotoxicity at relatively low paracetamol doses. Simultaneous alcohol and paracetamol ingestion reduces oxidative metabolism of paracetamol in both rodents and humans, predominantly as a consequence of depletion in cytosol of free NADPH. The possibilities that chronic alcohol use may predispose to paracetamol-related hepatotoxicity and that alcohol taken with paracetamol may protect against it, based on these metabolic observations, are examined in this review.

Treatment strategies for early presenting acetaminophen overdose: a survey of medical directors of poison centers in North America and Europe

BACKGROUND

Acetaminophen is frequently used in self-poisoning in Western countries. Although treatment with N-acetylcysteine (NAC) reduces liver injury, no consensus exists on the preferred management of acetaminophen toxicity.

OBJECTIVES

To describe the approach taken by toxicologists in North America and Europe toward the management of acetaminophen toxicity.

METHODS

Medical directors of poison centers in the US, Canada, and Europe were surveyed by means of a questionnaire presenting two clinical scenarios of acetaminophen overdose: a healthy adolescent with no risk factors who had an acute ingestion of acetaminophen, and an adult with both acute ingestion and possible risk factors. For each case, several questions about the management of these patients were asked.

RESULTS

Questionnaires were sent to medical directors of 76 poison centers in North America and 48 in Europe, with response rates of 62% and 44%, respectively. Forty percent of responders suggested using charcoal 4 hours after ingestion of a potential toxic dose of acetaminophen, and 90% recommended treatment with NAC when levels were above 150 microg/mL but below 200 microg/mL 4 hours after ingestion. Duration of treatment with oral NAC ranged from 24 to 96 hours; 38 responders suggested a duration of 72 hours. Of 49 centers recommending oral NAC, 18 (36.7%) said they might consider treatment for less than 72 hours. Eleven of 29 (37.9%) responders suggested treatment with intravenous NAC for more than 20 hours as their usual protocol or a protocol for specific circumstances.

CONCLUSIONS

Our study showed large variability in the management of acetaminophen overdose. Variations in treatment protocols should be addressed in clinical trials to optimize the treatment for this common problem.

A NO-releasing derivative of acetaminophen spares the liver by acting at several checkpoints in the Fas pathway

NCX-701 is a nitric oxide (NO)-releasing acetaminophen (APAP) derivative. In the present study we demonstrated that NCX-701 is as effective as APAP in controlling body temperature in a rat model of endotoxin-induced fever. Liver toxicity is a major complication of APAP overdosing. To investigate whether NCX-701 is hepatotoxic, BALB/C mice were injected with 100 - 500 mg kg(-1) APAP or NCX-701 alone or in combination (i.e. 500 mg kg(-1) of both compounds). Our results demonstrated that although APAP caused a dose-dependent liver injury, NCX-701 was completely devoid of liver toxicity. At the dose of 500 mg kg(-1) APAP caused an approximately 40 fold increase of AST plasma levels and extensive centrilobular necrosis. APAP and NCX-701 share the same metabolic pathway as demonstrated by the time-course of APAP-glucuronide concentrations in plasma and liver. NCX-701 was safe in mice with pre-existing chronic liver disease. Indeed, while C57BL6 transgenic mice expressing the hepatitis B virus (HBV) at the age of 8 months were significantly more susceptible to liver damage induced by APAP (500 mg kg(-1)) than their congenic littermates, treating HBV-transgenic mice with NCX-701, 500 mg kg(-1), caused no damage. Co-administration of NCX-701 at the dose 500 mg kg(-1) to mice treated with APAP, 500 mg kg(-1), completely protected against liver damage induced by APAP. APAP, but not NCX-701, upregulated liver Fas and Fas Ligand mRNA expression in vivo. Incubating mouse hepatocytes with APAP, but not with NCX-701, increased cell surface Fas expression and sensitized hepatocytes to death induced by challenge with a Fas-agonistic antibody. Collectively, these observations suggest that APAP toxicity is Fas mediated and that NCX-701 spares the liver by acting at several checkpoints in the Fas pathway.

Measuring plasma paracetamol concentrations in all patients with drug overdose or altered consciousness: does it change outcome?

OBJECTIVE

To assess whether measuring plasma paracetamol concentrations in all patients with drug overdose or collapse (altered consciousness) changes outcome.

METHOD

A retrospective survey was performed of all patients attending the Accident and Emergency Department at Guy's Hospital, London over a 12 month period who had plasma paracetamol concentrations measured (it is hospital policy that patients presenting after any drug overdose, or with a collapse/altered consciousness have a plasma paracetamol concentration).

RESULTS

A total of 440 patients were identified who had plasma paracetamol concentrations measured, of whom 411 were eligible for the study. Altogether 115 patients presented after a collapse and paracetamol was detected in four of these. A total of 296 patients presented after a drug overdose-136 denied overdose with a paracetamol containing product and paracetamol was not detected in any of these 136 cases. Of the remaining 160 patients who gave a positive history for overdose with paracetamol, 122 presented within 24 hours and 94 had detectable paracetamol values with 16 cases above the treatment line, 12 presented more than 24 hours after ingestion, and 26 presented with a staggered overdose. One patient died as a result of paracetamol overdose.

CONCLUSIONS

This is the first study in the United Kingdom to evaluate the clinical value of routine paracetamol levels in patients presenting to the emergency department after any overdose or a collapse. Taking blood samples for plasma paracetamol estimation in patients who deny taking paracetamol is of little clinical value. However, there is the potential for missing significant paracetamol poisoning in patients presenting with collapse and so screening with a plasma paracetamol concentration is clinically justified in these patients. Such an approach can only be justified in a country in which paracetamol poisoning is prevalent, such as the United Kingdom.

Risk factors in the development of adverse reactions to N-acetylcysteine in patients with paracetamol poisoning

AIMS

To identify risk factors in the development of side-effects to N-acetylcysteine (NAC) in patients with paracetamol poisoning.

METHODS

A retrospective study was carried out based upon the hospital charts of 529 consecutive patients admitted with paracetamol poisoning, all treated with NAC, at the Department of Hepatology, Copenhagen University Hospital (the tertiary care centre of liver disease in Denmark).

RESULTS

Forty-five patients (8.5%; 95% confidence intervals (CI) 6.4, 11%) developed side-effects to NAC and 18 patients (3.4%; 95% CI 2.1, 5.4%) developed systemic side-effects. Asthmatics were 2.9 times (95% CI 2.1, 4.7) more likely to develop side-effects (Chi-square: P = 0.004). Side-effects were of similar severity in asthmatics and nonasthmatics. A history of medical allergy was not a risk factor. Serum paracetamol was lower in patients with side-effects than in those without (Mann-Whitney: P = 0.00006).

CONCLUSIONS

Asthma must be considered a risk factor in the development of side-effects to NAC. However, the side-effects are easily managed and there is no reason to withhold NAC from any patient with paracetamol poisoning. Paracetamol itself seems to offer some protection against the development of side-effects to NAC.

Unintentional acetaminophen ingestion in children and the potential for hepatotoxicity

OBJECTIVE

Children who unintentionally ingest acetaminophen are often referred to health care facilities for evaluation. Criteria for referral are not well defined and the vast majority of these exposures result in nontoxic serum concentrations. The objective of this study was to determine the incidence of potentially hepatotoxic serum concentrations and to more clearly define referral criteria for these patients.

METHODS

A prospective evaluation of all childhood (age 1-72 months) single ingestions of acetaminophen-containing products was performed by the Utah Poison Control Center. All patients ingesting 140 mg/ kg or greater or an unknown amount were referred for medical evaluation. Patients who ingested greater than 100 mg/kg were advised to administer syrup of ipecac at home if less than 1 hour since ingestion. Activated charcoal was recommended within 2 hours of ingestion if the patient was already at a health care facility. The potential for hepatotoxicity was assessed according to the Rumack-Matthew nomogram.

RESULTS

Inclusion criteria were met by 1015 patients. The mean age was 28 +/- 12 months and mean dose was 213 +/- 148 mg/ kg. Decontamination with ipecac, gastric lavage, or activated charcoal within 2 hours of ingestion occurred in 81% of patients ingesting greater than 140 mg/kg or an unknown amount. Six patients (0.59%, 95% CI 0.12-1.16%) had "possible" or "probable" hepatotoxic serum concentrations and all had ingested greater than 200 mg/kg or an unknown amount. There were 423 patients who ingested between 100 and 200 mg/kg and none had potentially hepatotoxic serum concentrations (upper 95% CL 0.71%).

CONCLUSIONS

Children who ingest between 140-200 mg/kg of acetaminophen and demonstrate ipecac-induced emesis within 60 minutes may be safely managed at home. Patients ingesting greater than 200 mg/kg or an unknown amount should be referred for a serum acetaminophen concentration.

Paracetamol, alcohol and the liver

It is claimed that chronic alcoholics are at increased risk of paracetamol (acetaminophen) hepatotoxicity not only following overdosage but also with its therapeutic use. Increased susceptibility is supposed to be due to induction of liver microsomal enzymes by ethanol with increased formation of the toxic metabolite of paracetamol. However, the clinical evidence in support of these claims is anecdotal and the same liver damage after overdosage occurs in patients who are not chronic alcoholics. Many alcoholic patients reported to have liver damage after taking paracetamol with 'therapeutic intent' had clearly taken substantial overdoses. No proper clinical studies have been carried out to investigate the alleged paracetamol-alcohol interaction and acute liver damage has never been produced by therapeutic doses of paracetamol given as a challenge to a chronic alcoholic. The paracetamol-alcohol interaction is complex; acute and chronic ethanol have opposite effects. In animals, chronic ethanol causes induction of hepatic microsomal enzymes and increases paracetamol hepatotoxicity as expected (ethanol primarily induces CYP2E1 and this isoform is important in the oxidative metabolism of paracetamol). However, in man, chronic alcohol ingestion causes only modest (about twofold) and short-lived induction of CYP2E1, and there is no corresponding increase (as claimed) in the toxic metabolic activation of paracetamol. The paracetamol-ethanol interaction is not specific for any one isoform of cytochrome P450, and it seems that isoenzymes other than CYP2E1 are primarily responsible for the oxidative metabolism of paracetamol in man. Acute ethanol inhibits the microsomal oxidation of paracetamol both in animals and man. This protects against liver damage in animals and there is evidence that it also does so in man. The protective effect disappears when ethanol is eliminated and the relative timing of ethanol and paracetamol intake is critical. In many of the reports where it is alleged that paracetamol hepatotoxicity was enhanced in chronic alcoholics, the reverse should have been the case because alcohol was actually taken at the same time as the paracetamol. Chronic alcoholics are likely to be most vulnerable to the toxic effects of paracetamol during the first few days of withdrawal but maximum therapeutic doses given at this time have no adverse effect on liver function tests. Although the possibility remains that chronic consumption of alcohol does increase the risk of paracetamol hepatotoxicity in man (perhaps by impairing glutathione synthesis), there is insufficient evidence to support the alleged major toxic interaction. It is astonishing that clinicians and others have unquestion-ingly accepted this supposed interaction in man for so long with such scant regard for scientific objectivity.

Platelet dysfunction after intravenous ketorolac or propacetamol

BACKGROUND

Paracetamol is a weak cyclo-oxygenase inhibitor in vitro. A recent study in children has shown that high doses of paracetamol are effective and safe. We studied the effect of propacetamol on haemostasis in adult volunteers.

METHODS

Ten volunteers were investigated in a double-blind, randomized, crossover study. They received propacetamol 60 mg kg(-1) or ketorolac 0.4 mg kg(-1) in saline i.v. (30 min) in two different sessions. Platelet function was evaluated before the test infusion (S-0), two (S-2) and 24 h (S-24) after the start of the infusion. Coagulation parameters (PT, APTT, factor V and VII activities) were measured at S-0, S-24 and 48 h (S-48).

RESULTS

One of the volunteers had no secondary platelet aggregation in S-0 and was excluded from the final analysis. Two hours (S-2) after propacetamol and ketorolac administration the adrenaline (0.9 microg ml(-1) and 9.0 microg ml(-1)) induced maximal platelet aggregation was decreased compared with S-0. At S-2 platelet aggregation was inhibited more after ketorolac than after propacetamol. At 24 h after ketorolac, but not after propacetamol, there was still a decrease in the adrenaline-induced maximal platelet aggregation. Propacetamol did not affect adenosine diphosphate (ADP)-induced maximal platelet aggregation, whereas ketorolac decreased 3 and 6 microM ADP-induced maximal platelet aggregation at S-2 and S-24. However, 2 h after both ketorolac and propacetamol, thromboxane B2 (TxB2) concentration decreased in platelet rich plasma after 5 min aggregation induced by 8 microM ADP. Coagulation was unaffected.

CONCLUSION

Propacetamol 60 mg kg(-1) i.v. causes reversible platelet dysfunction demonstrated by a decrease in maximal platelet aggregation and TxB2 concentration. After 0.4 mg kg(-1) ketorolac i.v. platelet aggregation and TxB2 formation are inhibited more in comparison with propacetamol, and platelet dysfunction is still seen after 24 h.

Acute liver failure induced by alcohol and paracetamol in an HCV-infected haemophiliac

Paracetamol (acetaminophen) is frequently used by haemophiliacs in the management of acute or chronic pain, primarily due to its lack of adverse effects when taken at therapeutic doses. We describe acute hepatic and renal toxicity of paracetamol in a 36-year-old patient with haemophilia B, chronic hepatitis C and chronic alcohol abuse. Moderate doses of paracetamol (6 g/d for 4 d), taken with therapeutic intent, resulted in life-threatening organ dysfunction which gradually recovered with full supportive care.