Hepatotoxicity due to repeated intake of low doses of paracetamol

Hepatorenal Protective Effects of Hydroalcoholic Extract of Solidago canadensis L. against Paracetamol-Induced Toxicity in Mice

Paracetamol (AKA acetaminophen) is a widely used drug and is used for mild to moderate pains, such as mild osteoarthritis, toothache, headache, and pain caused by minimally invasive surgeries. Despite being a harmless drug in lower doses, acetaminophen can be toxic to the liver and kidneys if overdosed and even results in death. In this study, the therapeutic effects of Solidago canadensis L. extract (SCE) were investigated. 48 adult male Swiss albino mice (20-30 grams) were randomly divided into six groups of 8. The control group was gavaged with normal saline every 12 hours for 6 days. The second group received paracetamol at a 500 mg/kg intraperitoneally (i.p) dose on the sixth day. The third, fourth, and fifth groups were gavaged doses of 125, 250, and 500 mg/kg of SCE every 12 hours for six days, respectively, and on the sixth day, we received paracetamol at a dose of 500 mg/kg i.p. The sixth group only received SCE every 12 hours at a dose of 1000 mg/kg via gavaging for six days. On the seventh day (24 hours after paracetamol injection), blood samples were collected to measure the serum level of creatinine, uric acid, blood urea nitrogen (BUN), total protein, albumin, alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and total and direct bilirubin, and liver and kidney tissues were also sampled for histopathological examination. It was observed that paracetamol caused a considerable increase in the ALT, AST, ALP, uric Acid, and BUN levels (P < 0.01), while those in SCE-treated groups were significantly lower. In addition, various lesions in the paracetamol group were observed, while in the SCE-receiving groups, receiving prophylactic SCE inhibited the high-intense lesions such as the infiltration of inflammatory cells, hyperemia, and vacuolar degeneration, which decreased significantly in the control group in comparison with that of the paracetamol group (P < 0.05). In conclusion, SCE can have substantial protective effects against paracetamol's hepatorenal toxicity.

Comparative Study of Protective Effect of Cimetidine and Verapamil on Paracetamol-Induced Hepatotoxicity in Mice

Paracetamol, chemically known as acetaminophen, if taken in higher doses has hepatotoxic potential. Cimetidine by inhibiting the cytochromal enzymes and reducing the production of the toxic metabolite can reduce the hepatotoxic potential while Verapamil can act as a hepatoprotective by maintaining calcium homeostasis. The present study was conducted to study the hepatoprotective activity of Cimetidine and Verapamil against the toxicity induced by paracetamol. In addition to the group receiving only distilled water or 300 mg/kg paracetamol additional groups were added treated with 150 mg/kg Cimetidine and Verapamil alone or both. The Liver function tests and histopathology revealed hepatotoxicity in the group receiving paracetamol (PCM) while normal parameters were observed in the groups receiving Cimetidine and Verapamil. Our results strongly suggested that Cimetidine and Verapamil possess hepatoprotective potential against paracetamol induced hepatotoxicity.

Hepatotoxicity risk factors and acetaminophen dose adjustment, do prescribers give this issue adequate consideration? A French university hospital study

BACKGROUND

The hepatotoxicity of acetaminophen is recognised worldwide. Unfavourable prognoses relating to overdose include liver transplantation and/or death. Several hepatotoxicity risk factors (HRFs) should motivate the adjustment of acetaminophen daily intake (to < 4 g/day): advanced age, weight < 50 kg, malnutrition, chronic alcoholism, chronic hepatitis B and C and HIV infection, severe chronic renal failure and hepatocellular insufficiency.

METHOD

Over a 7-day period in Rennes University Hospital in December 2017, using DxCare® software, with an odds ratio estimation, we analysed all acetaminophen prescriptions, to assess to what extent the presence of HRFs altered the prescribers' choice of acetaminophen dose (< 4 g/day versus 4 g/day).

RESULTS

Among 1842 patients, considering only the first acetaminophen prescription, 73.7% were on 4 g/day. Almost half this population had at least 1 HRF. Whereas around 80% of the prescriptions in the < 4 g/day group were for patients with at least 1 HFR, only 53% of the prescriptions in the 4 g/day group concerned patients without HFRs (p < 0.001). Age > 75 and low weight were associated with the prescriber's choice of dose. Neither chronic alcoholism nor hepatocellular insufficiency influenced the acetaminophen doses prescribed.

CONCLUSION

Considering the widespread use of acetaminophen and its favourable safety profile compared with other analgesic drugs, it appears urgent to remind prescribers of the maximum daily dose recommendations for acetaminophen for patients with HRFs, especially those with chronic alcoholism and hepatocellular insufficiency.

Dietary supplementation with cysteine prevents adverse metabolic outcomes of repeated cures with paracetamol in old rats

Cysteine (Cys), a conditionally indispensable amino acid, is required for the detoxification of paracetamol (acetaminophen, N-acetyl-para-aminophenol, 4-hydroxy-acetanilide, APAP), a drug of widespread use in older persons. We recently reported that repeated APAP cures could worsen sarcopenia in old rats, likely to be due to the impairment of Cys/GSH homoeostasis. The aim of the study was to evaluate whether a dietary Cys supplementation during APAP cures could improve Cys/GSH homoeostasis and thus preserve skeletal muscle. Male 21·5-month-old Wistar rats received three 2-week-long cures of APAP (1 % of diet) alone or with extra Cys (0·5 % of diet), intercalated with washout periods of 2 weeks (APAP and APAP-Cys groups, respectively). They were compared with untreated control rats (CT group). CT and APAP-Cys groups were pair-fed to the APAP group. Dietary Cys supplementation was efficient to prevent increase in liver mass (P<0·0001), decrease in liver GSH (P<0·0001), increase in blood GSH concentration (P<0·0001), and to some extent, decrease in plasma free Cys concentration (P<0·05), all induced by repeated APAP cures. The addition of Cys to APAP cures decreased plasma alanine transaminase (P<0·05), the fractional synthesis rate of liver proteins (P<0·01), and increased masses of extensor digitorum longus (P<0·01), and soleus (P<0·05), compared with the APAP group. Cys supplementation prevented alteration in Cys/GSH homoeostasis and increased some muscle masses in old rats under repeated cures with a non-toxic dose of APAP.

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

Purpose

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

Method

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

Results

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

Conclusion

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

Electronic supplementary material

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

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

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

Evaluation of the hepatroprotective and nephroprotective activities of Scrophularia hypericifolia growing in Saudi Arabia

The hepatroprotective and nephroprotective effects of the ethanol extract of the aerial parts of Scrophularia hypericifolia growing in Saudi Arabia were evaluated at 250 and 500 mg kg(-1) doses using Wistar albino rats as experimental animal model. Toxic doses of paracetamol were used to induce liver and kidney toxicities, while the standard drug silymarin was used as reference. The biochemical parameters such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma glutamyl transpeptidase (GGT) and total bilirubin were estimated as reflections of the liver condition. Kidney condition was investigated through measurement of serum urea, serum creatinine, sodium and potassium levels. Liver and kidney samples of rats treated with 500 mg kg(-1) of the extract were subjected to the histopathological study. The ethanol extract of the aerial parts of S. hypericifolia showed dose dependent moderate level of protection against paracetamol induced hepatrotoxicity and nephrotoxicity as indicated from the obtained results. The reduction of the sodium and potassium levels by the higher dose of the extract exceeded that obtained by silymarin.

Antioxidant and Hepatoprotective Properties of Tofu (Curdle Soymilk) against Acetaminophen-Induced Liver Damage in Rats

The antioxidant and hepatoprotective properties of tofu using acetaminophen to induce liver damage in albino rats were evaluated. Tofus were prepared using calcium chloride, alum, and steep water as coagulants. The polyphenols of tofu were extracted and their antioxidant properties were determined. The weight gain and feed intake of the rats were measured. The analysis of serum alanine aminotransferase (ALT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) activities and the concentrations of albumin, total protein, cholesterol, and bilirubin were analyzed. The result reveals that the antioxidant property of both soluble and bound polyphenolic extracts was significantly higher in all tofus, but the steep water coagulated tofu was recorded higher. Rats fed with various tofus and acetaminophen had their serum ALP, ALT, AST, and LDH activities; total cholesterol; and bilirubin levels significantly (P < 0.05) reduced, and total protein and albumin concentrations increased when compared with basal diet and acetaminophen administered group. Therefore, all tofus curdled with various coagulants could be used to prevent liver damage caused by oxidative stress.

Hepatoprotective activity of dried- and fermented-processed virgin coconut oil

The present study aims to determine the hepatoprotective effect of MARDI-produced virgin coconut oils, prepared by dried- or fermented-processed methods, using the paracetamol-induced liver damage in rats. Liver injury induced by 3 g/kg paracetamol increased the liver weight per 100 g bodyweight indicating liver damage. Histological observation also confirms liver damage indicated by the presence of inflammations and necrosis on the respective liver section. Interestingly, pretreatment of the rats with 10, but not 1 and 5, mL/kg of both VCOs significantly (P < .05) reduced the liver damage caused by the administration of paracetamol, which is further confirmed by the histological findings. In conclusion, VCO possessed hepatoprotective effect that requires further in-depth study.

Systems biology approach to study permeability of paracetamol and its solid dispersion

Physiological changes that take place at cellular level are usually reflective of their level of gene expression. Different formulation excipients have an impact on physiological behavior of the exposed cells and in turn affect transporter genes, enterocyte-mediated metabolism and toxicity biomarkers. The aim of this study was to prepare solid dispersion of paracetamol and evaluate genetic changes that occur in Caco-2 cell lines during the permeability of paracetamol alone and paracetamol solid dispersion formulations. Paracetamol-PEG 8000 solid dispersion was prepared by melt fusion method and the formulation was characterised using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Formulation of solid dispersion resulted in the conversion of crystalline drug into an amorphous form. Permeability studies showed that paracetamol absorption was higher from the solid dispersion formulation. DNA microarrays analysis was carried out in order to investigate the involvement of any efflux/uptake transporters in paracetamol or its solid dispersion permeability. Neither transporter carriers nor efflux proteins were found to be involved in the absorption of paracetamol or its PEG solid dispersion. Gene expression analysis established that paracetamol toxicity was potentially reduced upon formulation into solid dispersion when ATP binding cassette (ABC) and solute carrier transporter (SLC) genes were analyzed.

Emergency orthogeriatrics: concepts and therapeutic alternatives

Multidisciplinary orthogeriatric care can enhance prompt ED diagnosis, optimal pre- and postoperative care, and functional recovery in older adults with bony injuries. Emergency care providers should be cognizant of prevalent geriatric syndromes including delirium and standing level falls to minimize fracture-related morbidity. Recognizing the implications of aging physiology, acute care physicians should be aware of effective alternatives to analgesia, procedural sedation, and definitive imaging to promote early surgical management and postoperative recovery.

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

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

Acetaminophen usage patterns and concentrations of glutathione and gamma-glutamyl transferase in alcoholic subjects

STUDY OBJECTIVES

To determine if subjects with chronic alcoholism are predisposed to acetaminophen-induced hepatotoxicity, and to determine the contributing factors.

DESIGN

Prospective cohort study.

SETTING

Community-based crisis intervention center.

SUBJECTS

One hundred eighty-eight subjects who answered "yes" to at least one of the four questions on the CAGE (Cut down-Annoyed-Guilty-Eye-opener) questionnaire for identifying alcoholism, and 10 healthy volunteers (controls).

INTERVENTION

A history, physical examination, urine toxicologic analysis, ethanol and drug therapy history, and venous blood samples were collected on all subjects.

MEASUREMENTS AND MAIN RESULTS

Venous blood was analyzed for a liver profile, prothrombin time, and total and oxidized glutathione concentrations. A significantly higher proportion of daily drinkers were regular daily users (29.2% [45/154] vs 11.8% [4/34], p=0.0497) as well as abusers (35.7% [55/154] vs 14.7% [5/34], p=0.0237) of acetaminophen compared with non daily drinkers. Alcoholic subjects with elevated gamma-glutamyl transferase (GGT >or= 51 U/L) levels had significantly lower median plasma glutathione concentrations (2.33 micromol/L, 95% confidence interval [CI] 1.74-2.69 micromol/L) compared with those of alcoholic subjects with normal GGT concentrations (5.97 micromol/L, 95% CI 4.39-7.03 micromol/L, p<0.0001) and healthy volunteers (6.59 micromol/L, 95% CI 4.79-9.65 micromol/L, p=0.0002). A significant inverse correlation was also noted between the GGT concentration and the plasma total glutathione concentration (r = -0.62, p<0.0001). None of the 188 subjects met all preset criteria for hepatotoxicity.

CONCLUSIONS

Daily drinkers were more than twice as likely as non daily drinkers to be regular daily acetaminophen users and abusers. Alcoholic subjects with elevated GGT concentrations had significantly lower plasma total glutathione concentrations, and plasma total glutathione concentrations inversely correlated with GGT concentrations. Elevated GGT concentrations may be a clinical marker of depleted glutathione in alcoholic subjects. Acetaminophen-induced hepatotoxicity appears to be uncommon in alcoholic subjects, despite the 31.9% (60/188 patients) who took doses that are potentially hepatotoxic.

Does therapeutic use of acetaminophen cause acute liver failure?

STUDY OBJECTIVE

To compare the reported occurrence of liver failure in subjects in prospective trials with that in patients in retrospective reports after repeated use of therapeutic dosages of acetaminophen.

DESIGN

Systematic review of the medical literature.

DATA SOURCE

MEDLINE and EMBASE biomedical and pharmacologic databases.

SUBJECTS

Adults who received repeated dosing of acetaminophen 4 g/day or lower for at least 24 hours.

MEASUREMENTS AND MAIN RESULTS

Articles written in several languages were abstracted by trained personnel using a structured abstraction form. Data were categorized by methodology (prospective vs retrospective), acetaminophen dosage, and type of liver effect. A total of 791 articles were identified, which included 30,865 subjects in prospective studies and 9337 patients in retrospective reports. The prospective studies reported no cases of fulminant hepatic injury, liver transplantation, or death due to acetaminophen. Of the 30,865 subjects in these studies, 129 (0.4%) were identified who had a serum aminotransferase level that exceeded the upper limit of normal, including 61 subjects in randomized trials in which the proportion of serum aminotransferase level increase was the same as or less than that in the placebo group and 68 subjects in trials without a placebo group. In addition, 4263 (13.8%) received the maximum recommended therapeutic dosage (3.9-4 g/day). In the retrospective reports, 96 patients (1.0%) had a serum alanine aminotransferase level that exceeded the upper limit of normal, one (0.01%) underwent liver transplantation, and six (0.06%) died. Causality relationship of acetaminophen for each retrospective case was assessed with the Naranjo adverse drug reaction probability scale. The mean +/- SD Naranjo score for all 103 retrospective cases was 3.2 +/- 1.9, indicating a possible relationship between the increased aminotransferase levels and acetaminophen use. Some retrospective reports contained information suggesting that the patient had ingested an overdose despite a history of therapeutic use.

CONCLUSION

Prospective studies indicated that repeated use of a true therapeutic acetaminophen dosage may slightly increase the level of serum aminotransferase activity, but hepatic failure or death was not reported. Retrospective reports indicated a higher rate of increased serum aminotransferase levels, and several reported associated liver injury and death. The differing results and presence of evidence indicating inaccurate acetaminophen dosage information in some case reports suggests that these cases may be inadvertent overdoses, rather than true therapeutic dosages.

Acetaminophen safety and hepatotoxicity--where do we go from here?

Acetaminophen has been widely used for > 50 years in the treatment of pain and fever and provides for the safe and effective relief of these symptoms. In a small minority of patients, however, acetaminophen is responsible for life-threatening liver injury and accounts for up to 50% of all adult cases of acute liver failure in the US. Although approximately two-thirds of adult overdoses are associated with suicide attempts, many are inadvertent, often due to the use of multiple acetaminophen formulations over many days. Additionally, some individuals appear to experience acetaminophen toxicity at 'therapeutic' doses of < 4 g/day, for reasons unknown. In pediatric populations, the overwhelming majority of acetaminophen overdoses are due to unintentional overdoses, except for the predominance of suicidal ingestions in the teenage population. This article seeks to review the mechanism and metabolism of acetaminophen and the features of toxicity in adults, pediatric and special populations. Additionally, expert opinion is presented herein to aid in reducing the frequency and severity of liver injury from acetaminophen.

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.

Fulminant hepatic failure and paracetamol overuse with therapeutic intent in febrile children

OBJECTIVE

To evaluate the risk of fulminant hepatic failure in relation to paracetamol overuse with therapeutic intent in febrile children.

METHODS

It was a case control study. Paracetamol ingestion for the current febrile illness was compared between 25 cases of fulminant hepatic failure and 33 hospital age matched controls.

RESULTS

Supra-therapeutic doses of paracetamol (mean 145 mg/kg/day) were consumed by all 25 cases compared to none in the control group. Mean paracetamol level in the cases and controls were, respectively, 26.84 mg /dl and 0.051 mg /dl (p< 0.001). The mean duration of paracetamol intake prior to admission in cases was 3. 45 days compared to 1.85 days in the control group. Nineteen, 5 and 3 were, respectively, graded as hepatic encephalopathy grade 1, 2 and 3. All six patients in grade 2 and 3 had hepatomegaly compared to 78% in the grade 1. Four had jaundice and all were in grade 2 or 3. Mean alanine aminotransferase was 2781 U/L None of the randomly selected cases (6) had serological evidence of Hepatitis A, Hepatitis B or Dengue. Three cases died.

CONCLUSION

Exposure to multiple supratherapeutic doses of paracetamol is a risk factor to develop fulminant hepatic failure in children with an acute viral like febrile illness.

Repeated supratherapeutic doses of paracetamol in children--a literature review and suggested clinical approach

The safety of paracetamol when given in the recommended dosage is well documented. However, in recent years there have been many reports of liver failure associated with repeated exposure to supratherapeutic doses of paracetamol. This paper reviews the literature on chronic supratherapeutic paracetamol exposure in children and the different dosing guidelines. Based on which, we suggest the following approach: liver injury secondary to repeated dosing of paracetamol should be considered when a child has received more than 75 mg/kg/d for at least 2 d, or if risk factors for paracetamol toxicity have been identified. Liver transaminases, coagulation factors, and paracetamol serum concentrations should be measured in these children and in symptomatic children with vomiting, right upper quadrant abdominal pain, and jaundice who have taken paracetamol. Treatment with N-acetyl cysteine should be started regardless of paracetamol concentrations if transaminases or INR are elevated.

CONCLUSION

Liver injury secondary to repeated dosing of paracetamol is rare but may result in severe morbidity and mortality. The cumulative dose of paracetamol should not exceed 75 mg/kg/d. Children treated with higher doses for more than 2 d should be evaluated for possible liver injury and treated with N-acetyl cysteine if evidence of liver injury is found.

Severe hepatotoxicity after therapeutic doses of acetaminophen

BACKGROUND

Acetaminophen overdose is a frequent cause of acute liver failure. Controversy exists over the rare association of severe hepatotoxicity or acute liver failure with therapeutic doses of acetaminophen.

CASE SUMMARY

A 45-year-old white man weighing 85 kg with asymptomatic HIV, hepatitis B virus, and hepatitis C virus (HCV) infection presented with signs of severe hepatotoxicity: aspartate aminotransferase (AST), 8,581 IU/L; alanine aminotransferase (ALT), 5,433 IU/L; L-lactate dehydrogenase, 13,641 IU/L; and prothrombin international normalized ratio, 2.15. He reported taking acetaminophen 1,000 mg QID for the previous 4 days and 1,000 mg that morning because of a febrile illness. Immediate administration of continuous IV N-acetylcysteine 150 mg/kg for the first 90 minutes and then 50 mg/kg q4h for the next 3 days was followed by clinical improvement and a rapid decrease in AST and ALT. AST levels decreased from 8,581 to 42 IU/L within 11 days. Several potential risk factors for acetaminophen hepatotoxicity (ie, chronic alcohol, tobacco, and opiate consumption, malnutrition, illness-induced starvation, HIV infection, and HCV infection) were present in this patient.

CONCLUSIONS

This patient with multiple risk factors and severe hepatotoxicity after therapeutic dosage of acetaminophen was successfully treated with N-acetylcysteine.

Protective effects of Swertia longifolia Boiss. and its active compound, swerchirin, on paracetamol-induced hepatotoxicity in mice

Aerial parts of Swertia longifolia Boiss. (Gentianaceae), which grows in the north of Iran, were screened for hepatoprotective activity against paracetamol (acetaminophen)-induced hepatotoxicity in Swiss mice. Pretreatment with total plant extract and swerchirin, the major component of the plant, significantly reduced the elevation of biochemical parameters, AST (aspartate aminotransferase), ALT (alanine aminotransferase) and ALP (alkaline phosphatase), the enzymes that are increased by liver damage (P < 0.001). Our results indicated that total plant extract and swerchirin were hepatoprotective in the range of 6-50 mg kg(-1) orally.

Acetaminophen poisoning: an evidence-based consensus guideline for out-of-hospital management

The objective of this guideline is to assist poison center personnel in the appropriate out-of-hospital triage and initial management of patients with suspected ingestions of acetaminophen. An evidence-based expert consensus process was used to create this guideline. This guideline applies to ingestion of acetaminophen alone and is based on an assessment of current scientific and clinical information. The expert consensus panel recognizes that specific patient care decisions may be at variance with this guideline and are the prerogative of the patient and the health professionals providing care. The panel's recommendations follow. These recommendations are provided in chronological order of likely clinical use. The grade of recommendation is provided in parentheses. 1) The initial history obtained by the specialist in poison information should include the patient's age and intent (Grade B), the specific formulation and dose of acetaminophen, the ingestion pattern (single or multiple), duration of ingestion (Grade B), and concomitant medications that might have been ingested (Grade D). 2) Any patient with stated or suspected self-harm or who is the recipient of a potentially malicious administration of acetaminophen should be referred to an emergency department immediately regardless of the amount ingested. This referral should be guided by local poison center procedures (Grade D). 3) Activated charcoal can be considered if local poison center policies support its prehospital use, a toxic dose of acetaminophen has been taken, and fewer than 2 hours have elapsed since the ingestion (Grade A). Gastrointestinal decontamination could be particularly important if acetylcysteine cannot be administered within 8 hours of ingestion. Acute, single, unintentional ingestion of acetaminophen: 1) Any patient with signs consistent with acetaminophen poisoning (e.g., repeated vomiting, abdominal tenderness in the right upper quadrant or mental status changes) should be referred to an emergency department for evaluation (Grade D). 2) Patients less than 6 years of age should be referred to an emergency department if the estimated acute ingestion amount is unknown or is 200 mg/kg or more. Patients can be observed at home if the dose ingested is less than 200 mg/kg (Grade B). 3) Patients 6 years of age or older should be referred to an emergency department if they have ingested at least 10 g or 200 mg/kg (whichever is lower) or when the amount ingested is unknown (Grade D). 4) Patients referred to an emergency department should arrive in time to have a stat serum acetaminophen concentration determined at 4 hours after ingestion or as soon as possible thereafter. If the time of ingestion is unknown, the patient should be referred to an emergency department immediately (Grade D). 5) If the initial contact with the poison center occurs more than 36 hours after the ingestion and the patient is well, the patient does not require further evaluation for acetaminophen toxicity (Grade D). Repeated supratherapeutic ingestion of acetaminophen (RSTI): 1) Patients under 6 years of age should be referred to an emergency department immediately if they have ingested: a) 200 mg/kg or more over a single 24-hour period, or b) 150 mg/kg or more per 24-hour period for the preceding 48 hours, or c) 100 mg/kg or more per 24-hour period for the preceding 72 hours or longer (Grade C). 2) Patients 6 years of age or older should be referred to an emergency department if they have ingested: a) at least 10 g or 200 mg/kg (whichever is less) over a single 24-hour period, or b) at least 6 g or 150 mg/kg (whichever is less) per 24-hour period for the preceding 48 hours or longer. In patients with conditions purported to increase susceptibility to acetaminophen toxicity (alcoholism, isoniazid use, prolonged fasting), the dose of acetaminophen considered as RSTI should be greater than 4 g or 100 mg/kg (whichever is less) per day (Grade D). 3) Gastrointestinal decontamination is not needed (Grade D). Other recommendations: 1) The out-of-hospital management of extended-release acetaminophen or multi-drug combination products containing acetaminophen is the same as an ingestion of acetaminophen alone (Grade D). However, the effects of other drugs might require referral to an emergency department in accordance with the poison center's normal triage criteria. 2) The use of cimetidine as an antidote is not recommended (Grade A).

Measuring quality in arthritis care: The Arthritis Foundation's quality indicator set for analgesics

OBJECTIVE

To develop systematically validated quality indicators (QIs) addressing analgesic safety.

METHODS

A comprehensive literature review of existing quality measures, clinical guidelines, and evidence supporting potential QIs concerning nonselective (traditional) nonsteroidal anti-inflammatory drugs (NSAIDs) and newer cyclooxygenase 2-selective NSAIDs was undertaken. An expert panel then validated or refuted potential indicators utilizing a proven methodology.

RESULTS

Eleven potential QIs were proposed. After panel review, 8 were judged to be valid; an additional 10 were proposed by the panel, of which 7 were rated as valid. Quality indicators focused upon informing patients about risk, NSAID choice and gastrointestinal prophylaxis, and side effect monitoring.

CONCLUSION

The 15 validated indicators were combined, where appropriate, to yield 10 validated processes of care indicators for the safe use of NSAIDs. These indicators developed by literature review and finalized by our expert panel process can serve as a basis to compare the quality of analgesic use provided by health care providers and delivery systems.

Hepatoprotective activity of Trianthema portulacastrum L. against paracetamol and thioacetamide intoxication in albino rats

The ethanolic extract of Trianthema portulacastrum L. (Aizoaceae) showed a significant dose dependent (100 mg, 200 mg/kg p.o. 10x) protective effect against paracetamol and thioacetamide induced hepatotoxicity in albino rats. The degree of protection was measured by using biochemical parameters like serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), alkaline phosphatase (ALP), bilirubin (BRN), and total protein (TP). The plant extract completely prevented the toxic effects of paracetamol (acetaminophen) and thioacetamide on the above serum parameters. A significant hepatoprotective activity of the ethanolic extracts of Trianthema portulacastrum L. was reported.

Glutathione, glutathione-dependent enzymes and antioxidant status in erythrocytes from children treated with high-dose paracetamol

AIM

To investigate glutathione and antioxidant status changes in erythrocytes from febrile children receiving repeated supratherapeutic paracetamol doses.

METHODS

Fifty-one children aged 2 months to 10 years participated in the study. Three groups were studied: group 1 (n = 24) included afebrile children who did not receive paracetamol; and groups 2 (n = 13) and 3 (n = 14) included children who had fever above 38.5 degrees C for more than 72 h. Patients in group 2 received paracetamol at a dose of 50 +/- 15 (30-75) mg kg(-1) day(-1) and those in group 3 received paracetamol above the recommended therapeutic dose, ie 107 28 (80-180) mg kg(-1) day(-1). A blood sample was taken for the measurement of liver transaminases, gammaglutamil transferase (GGT), reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPX), glutathione S-transferase (GST), superoxide dismutase (SOD) and antioxidant status.

RESULTS

Aspartate aminotransferase activity in group 3 was higher than in the other groups (P = 0.027). GSH, SOD and antioxidant status were significantly lower in group 3 compared with groups 1 and 2 (mean differences: for GSH 3.41 micromol gHb(-1), 95% confidence interval (CI) 2.10-4.72, and 2.15 micromol gHb(-1), 95% CI 0.65-3.65, respectively; for SOD 856 U min(-1) gHb(-1), 95% CI 397-1316, and 556 U min(-1) gHb(-1), 95% CI 30-1082, respectively; and for antioxidant status 0.83 mmol l(-1) plasma, 95% CI 0.30-1.36, and 0.63 mmol l(-1) plasma, 95% CI 0.02-1.24, respectively). GR activity was significantly lower in groups 3 and 2 in comparison with group 1 (mean differences 3.44 U min(-1) gHb(-1), 95% CI 0.63-6.25, and 5.64 U min(-1) gHb(-1), 95% CI 2.90-8.38, respectively). Using multiple regression analysis, paracetamol dose was found to be the only independent variable affecting GR, GST and SOD activities (P = 0.007, 0.003 and 0.008, respectively).

CONCLUSIONS

In febrile children, treatment with repeated supratherapeutic doses of paracetamol is associated with reduced antioxidant status and erythrocyte glutathione concentrations. These significant changes may indicate an increased risk for hepatotoxicity and liver damage.

Paracetamol-induced hepatotoxicity at recommended dosage

In patients who develop liver damage following moderate paracetamol overdose in the order of 5-10 g daily, recent fasting and nutritional impairment have been identified as key precipitants. Hepatotoxicity caused by paracetamol at recommended dosage, in the absence of exposure to enzyme-inducing drugs, has recently been described as an idiosyncratic phenomenon. The possible importance of fasting and malnutrition in this setting is uncertain. We report a severely malnourished 53-year-old woman who developed severe hepatotoxicity whilst receiving paracetamol at recommended dosage (4 g daily) following a period of fasting, in the absence of enzyme-inducing agents. Subsequent paracetamol exposure up to 2.6 g daily thrice weekly, in the setting of ongoing malnutrition and fasting as before, did not lead to recurrent liver damage. These findings indicate that paracetamol-related liver damage occurring within recommended dosage guidelines can be a dose-dependent rather than necessarily idiosyncratic phenomenon, at least in the setting of recent fasting and severe malnutrition.

Approaches toward repeated supratherapeutic doses of paracetamol in children: a survey of medical directors of poison centres in North America and Europe

BACKGROUND

During the last few years there has been an increase in the number of reports of liver failure associated with prolonged paracetamol (acetaminophen) administration in children for therapeutic reasons.

OBJECTIVE

To describe the approach taken by medical directors of poison centres regarding the treatment of repeated supratherapeutic doses of paracetamol in children.

METHODS

Questionnaires mailed to the medical directors of 76 poison centres in North America and 48 poison centres in Europe asked respondents to comment on the management of a hypothetical case of a child who had received repeated doses of paracetamol at a daily dose of 90 mg/kg during a febrile illness and who presented to the emergency department with mildly elevated serum transaminase levels.

RESULTS

The response rate was 62% for North American centres and 44% for European centres. There was a wide range of answers regarding the maximal safe daily dose of paracetamol. For the case described, 71% of the respondents suggested measuring paracetamol serum concentration. Fifty-four percent suggested treating the patient with acetylcysteine and 35% suggested not treating the patient.

CONCLUSIONS

Our study showed that there is little agreement among medical directors of poison centres on the toxic threshold for chronic exposure to paracetamol in children and on how these cases should be managed.

Analgesics and glutathione

A growing body of evidence indicates that glutathione (GSH) plays a vitally important role in cellular function. It detoxifies toxic metabolites of drugs and reactive oxygen species and regulates gene expression, apoptosis, and transmembrane transport of organic solutes. The maintenance of GSH homeostasis is essential for the organism to perform its many functions. The turnover of GSH is a dynamic process, and large quantities of GSH are synthesized per day from its precursor amino acids cysteine, glutamic acid, and glycine. Toxic doses of paracetamol deplete intracellular GSH and result in cell death by a combination of mechanisms, leading to necrosis and apoptosis, mainly in the liver. In clinical situations characterized by low GSH, the risk of toxicity from therapeutic doses of paracetamol may conceivably be increased. This toxicity has been reported in chronic alcoholics who have low intrahepatic GSH and who may have an induced enzyme system that generates the toxic metabolite of paracetamol. Considering the large number of alcoholics in our population and the widespread use of paracetamol, this must be a rare and essentially unpredictable occurrence. Except for anecdotal reports, there is no convincing evidence that other populations in which low GSH has been observed-such as patients with human immunodeficiency virus (HIV) infection or chronic hepatitis C, malnourished patients, and patients with cirrhosis-are at higher risk of experiencing adverse events from paracetamol.

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.

Determination of acetaminophen-protein adducts in mouse liver and serum and human serum after hepatotoxic doses of acetaminophen using high-performance liquid chromatography with electrochemical detection

Acetaminophen-induced hepatotoxicity has been attributed to covalent binding of the reactive metabolite N-acetyl-p-benzoquinone imine to cysteine groups on proteins as an acetaminophen-cysteine conjugate. We report a high-performance liquid chromatography with electrochemical detection (HPLC-ECD) assay for the conjugate with increased sensitivity compared with previous methods. Previous methods to quantitate the protein-bound conjugate have used a competitive immunoassay or radiolabeled acetaminophen. With HPLC-ECD, the protein samples are dialyzed and then digested with protease. The acetaminophen-cysteine conjugate is then quantified by HPLC-ECD using tyrosine as an internal reference. The lower limit of detection of the assay is approximately 3 pmol/mg of protein. Acetaminophen protein adducts were detected in liver and serum as early as 15 min after hepatotoxic dosing of acetaminophen to mice. Adducts were also detected in the serum of acetaminophen overdose patients. Analysis of human serum samples for the acetaminophen-cysteine conjugate revealed a positive correlation between acetaminophen-cysteine conjugate concentration and serum aspartate aminotransferase (AST) activity or time. Adducts were detected in the serum of patients even with relatively mild liver injury, as measured by AST and alanine aminotransferase. This assay may be useful in the diagnostic evaluation of patients with hepatotoxicity of an indeterminate etiology for which acetaminophen toxicity is suspect.

Pathophysiology and first-line treatment of osteoarthritis

OBJECTIVE

To review the pathophysiology of osteoarthritis (OA) and the various treatment modalities, focusing specifically on acetaminophen (APAP), nonsteroidal antiinflammatory drugs (NSAIDs), and cyclooxygenase-2 (COX-2) inhibitors as the primary treatment options.

DATA SOURCES

Primary literature and tertiary references were identified by a MEDLINE search (1966-March 2001) and through other secondary sources.

STUDY SELECTION AND DATA EXTRACTION

After evaluating the articles and references identified from the data sources, all the information that was judged relevant by the reviewers was included in the review article.

DATA SYNTHESIS

OA is the most common joint disorder worldwide. Current research suggests that factors such as inflammation and changes in subchondral bone may play a larger role in the pathophysiology than previously thought. With this research and the development of COX-2 inhibitors, selecting the medication of choice for OA has become difficult.

CONCLUSIONS

More research needs to be done before the pathophysiology of OA can be clearly determined. In the meantime, treatment should be based on clinical data and patient response. Studies have shown that APAP and NSAIDs have comparable efficacy, as do traditional NSAIDs and COX-2 inhibitors. APAP is associated with fewer toxicities than are the traditional NSAIDs. Due to their mechanism of action, the new COX-2 inhibitors should result in fewer adverse effects compared with traditional NSAIDs, but evidence from clinical trials has not been conclusive. Therefore, APAP should still be considered the drug of choice for OA.

Management of paracetamol overdose: current controversies

Paracetamol (acetaminophen) is one of the most frequently used analgesics, and is the most commonly used substance in self-poisoning in the US and UK. Paracetamol toxicity is manifested primarily in the liver. Treatment with N-acetyl-cysteine (NAC), if started within 10 hours from ingestion, can prevent hepatic damage in most cases. Pharmacokinetic data relating plasma paracetamol concentration to time after ingestion have been used to generate a 'probable hepatoxicity line' to predict which cases of paracetamol overdose will result in hepatotoxicity and should be treated with NAC. However, later studies use a 25% lower line as their 'possible hepatotoxicity line'. Although adopting the original line may save considerable resources, further studies are needed to determine whether such an approach is safe. On the basis of the metabolism of paracetamol, several risk factors for paracetamol toxicity have been proposed. These risk factors include long term alcohol (ethanol) ingestion, fasting and treatment with drugs that induce the cytochrome P450 2E1 enzyme system. Although some studies have suggested that these risk factors may be associated with worse prognosis, the data are inconclusive. However, until further evidence is available, we suggest that the lower line should be used when risk factors are present. In Canada and the UK, the intravenous regimen for NAC is used almost exclusively; in the US, an oral regimen is used. Both regimens have been shown to be effective. There is no large scale study with direct comparison between these 2 therapeutic protocols and controversy still exists as to which regimen is superior. During the last few years there has been an increase in the number of reports of liver failure associated with prolonged paracetamol administration for therapeutic reasons. The true incidence of this phenomenon is not known. We suggest testing liver enzyme levels if a child has received more than 75 mg/kg/day of paracetamol for more than 24 hours during febrile illness, and to treat with NAC when transaminase levels are elevated. Paracetamol overdose during pregnancy should be treated with either oral or intravenous NAC according to the regular protocols in order to prevent maternal, and potentially fetal, toxicity. Unless severe maternal toxicity develops, paracetamol overdose does not appear to increase the risk for adverse pregnancy outcome.

Interventions for paracetamol (acetaminophen) overdoses

BACKGROUND

Self-poisoning with paracetamol (acetaminophen) is a common cause of hepatotoxicity in the Western World. Interventions for paracetamol poisoning encompass inhibition of absorption, removal from the vascular system, antidotes, and liver transplantation.

OBJECTIVES

The objective was to assess the beneficial and harmful effects of interventions or combination of interventions for paracetamol overdose.

SEARCH STRATEGY

The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Library, MEDLINE, EMBASE, and text searches were combined (until July 2001).

SELECTION CRITERIA

Randomised clinical trials (RCTs) and observational studies as well as human volunteer randomised trials were included. The studies could be unpublished or published as an article, an abstract, or a letter and no language limitations were applied.

DATA COLLECTION AND ANALYSIS

All the analyses were performed according to the intention to treat. The methodological quality of the included trials was evaluated by components of methodological quality.

MAIN RESULTS

Nine RCTs (all small and of low methodological quality), one quasi-randomised trials, 37 observational studies, and nine randomised trials including human volunteers were identified. It was impossible to perform meta-analyses including more than two RCTs. 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 (relative risk of mortality in patients with fulminant hepatic failure = 0.65; 95% confidence interval 0.43 to 0.99), 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 evidence supports haemoperfusion or cimetidine for paracetamol overdose. Liver transplantation has the potential to be life saving in fulminant hepatic failure, but further refinement of selection criteria for liver transplantation and evaluation of the long-term outcome are required.

REVIEWER'S CONCLUSIONS

This systematic Review has highlighted a paucity of RCTs on interventions for paracetamol overdose. Activated charcoal seems the best choice to reduce paracetamol absorption. N-acetylcysteine should be given to patients with paracetamol overdose. 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 in patients with a poor prognosis. Interventions for paracetamol overdose need assessment in high-quality, multi-centre RCTs.

Acetaminophen toxicity in children

Acetaminophen is widely used in children, because its safety and efficacy are well established. Although the risk of developing toxic reactions to acetaminophen appears to be lower in children than in adults, such reactions occur in pediatric patients from intentional overdoses. Less frequently, acetaminophen toxicity is attributable to unintended inappropriate dosing or the failure to recognize children at increased risk in whom standard acetaminophen doses have been administered. Because the symptoms of acetaminophen intoxication are nonspecific, the diagnosis and treatment of acetaminophen intoxication are more likely to be delayed in unintentional cases of toxicity. This statement describes situations and conditions that may contribute to acetaminophen toxicity not associated with suicidal intentions.

Evaluation of the protective potential of Ambrosia maritima extract on acetaminophen-induced liver damage

The hepatoprotective activity of the aqueous-methanolic extract of Ambrosia maritima was investigated against acetaminophen (paracetamol, 4-hydroxy acetanilide) induced hepatic damage. Acetaminophen at the dose of 640 mg/kg produced liver damage in rats as manifested by the significant (P < 0.001) rise in serum levels of glutamate oxaloacetate transaminase (AST), glutamate pyruvate transaminase (ALT) and alkaline phosphatase (ALP) to 1178.5 +/-118.05; 607.5 +/- 32.6 and 274.16 +/- 8.89 IU/l (n = 10), respectively, compared with respective control values of 97.83+/-3.23; 46.0 +/- 3.92 and 168.67 +/- 7.86 IU/l. Pretreatment of rats with the plant extract (100 and 200 mg/kg) lowered significantly (P < 0.001) the respective serum AST to 203.3+/-5.74 and 157.1 +/- 8.78 IU/l, ALT to 138.67 +/- 7.7 and 87.5 +/- 3.6 IU/l and ALP levels to 238.0 +/- 5.89 and 206.5 +/- 7.5 IU/l, respectively. Treatment of rats with acetaminophen led to a marked increase in lipid peroxidation as measured by malondialdehyde (MDA) (42%). This was associated with a significant reduction of the hepatic antioxidant system e.g. reduced glutathione (GSH) (65%), glutathione reductase (GSH-R) (35%), total glutathione peroxidase (GSH-Px) (32%) and glutathione-S-transferase (GST) (16%). These biochemical alterations resulting from acetaminophen administration were inhibited by pretreatment with A. maritima L. extract. These data suggest that the plant A. maritima L. may act as a hepatoprotective and antioxidant agent.

Evaluation of occult acetaminophen hepatotoxicity in hospitalized children receiving acetaminophen. Pediatric Pharmacology Research Unit Network

The safety of repeated doses of acetaminophen in ill children with the potential of reduced glutathione stores has been questioned. This study measured hepatic transaminases in children and adolescents (n=100) who received > or = 6 therapeutic doses of acetaminophen over a 48-hour period of hospitalization. Acetaminophen-protein adducts were measured in a cohort of subjects with hepatic transaminase elevation (n=8) and in those (n=10) receiving concurrent drug therapy with agents that induce the cytochrome P450 enzymes involved in acetaminophen metabolism. Acetaminophen-protein adducts were not detected in this cohort of 18 subjects. Based on this pilot study, the routine use of acetaminophen at therapeutic doses in ill, hospitalized children and adolescents appears safe.

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.

Acetaminophen hepatotoxicity: An update

Acetaminophen is a widely used nonprescription analgesic and antipyretic agent. It is also a dose-related hepatotoxin that can cause fulminant liver failure when taken in massive overdoses or, much less commonly, at therapeutic doses in susceptible individuals. Persons who regularly consume alcohol or persons who have been fasting may be more susceptible to this hepatotoxicity. This liver injury is due not to the drug itself but to the formation of the toxic metabolite N-acetyl-p-benzoquinine imine generated through the cytochrome P-450 drug-metabolizing system. Normally, hepatic stores of glutathione combine with the toxic metabolite and prevent liver cell injury. When glutathione stores are depleted by overproduction of this metabolite, however, the reactive metabolite binds to liver cell proteins and causes hepatic necrosis. P-450 2E1 is induced by alcohol consumption and possibly starvation, and glutathione depletion can occur due to the inadequate nutrition occurring in chronic alcohol use or in starvation. Recent studies have shown that activated Kupffer cells and their secreted toxic agents such as cytokines may also play a role in this liver injury. This liver injury is characterized by extremely high levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (> 1000), and bad prognostic signs include severe prolongation of the prothrombin time, renal dysfunction, and, most importantly, acidosis. N-acetylcysteine is a highly effective antidote when given early (within 15 hours) of overdose. Some patients may develop such fulminant liver injury that they require transplantation. Unfortunately, many such patients have a course so rapid that a donor liver may not become available in time. Thus, both the medical community and the general public require a heightened understanding of this clinical problem in order to initiate prevention measures and to implement early therapeutic measures if an overdose situation occurs.

The impact of nationally distributed guidelines on the management of paracetamol poisoning in accident and emergency departments. National Poison Information Service

OBJECTIVE

To assess the impact of the treatment guidelines on the management of paracetamol self poisoning in accident and emergency (A&E) departments.

METHODS

24 A&E departments in Wales and England provided details of their management of paracetamol poisoning before and after the distribution of national treatment guidelines to all A&E departments in the United Kingdom.

RESULTS

Significant increases were seen in the availability of formal written policies, the display of treatment nomograms, the recommendation to treat beyond 16 hours after ingestion, and to use a lower line on the treatment nomogram for patients at special risk of paracetamol induced liver damage.

CONCLUSIONS

Regularly updated guidelines in the management of paracetamol poisoning should be displayed in A&E departments so that medical and nursing personnel have access to the best current information on the treatment of poisoning with this frequently used drug.

Enhanced hepatotoxicity of acetaminophen in the alcoholic patient. Two case reports and a review of the literature

We report 2 fatal cases of the acetaminophen-alcohol syndrome and review 51 reported cases in the medical literature. The MEDLINE database from January 1966 to December 1995 and bibliographies of selected articles were used to obtain the case reports. Inclusion criteria were a clear history of alcohol use, a history of acetaminophen use and/or an elevated serum acetaminophen level, peak aspartate aminotransferase (AST) greater than 800 U/L, and exclusion of other causes of hepatotoxicity by negative hepatitis serologies and/or a liver biopsy showing typical findings of acetaminophen toxicity. Demographic characteristics, clinical features, treatment, and outcome were extracted from reports meeting inclusion criteria and our own 2 cases. This syndrome affected relatively young, frequently healthy patients. Acetaminophen was invariably taken for nonsuicidal intent. The mortality rate was 32%. A typical laboratory picture was defined, characterized by an extraordinarily high AST level. Treatment with N-acetylcysteine was not effective due to delayed presentation and diagnosis. Patients who use alcohol and health care providers should be educated about this potentially fatal syndrome. Prevention is the key to reducing its occurrence.

Comparison of thermally oxidized lipids and acetaminophen with concurrent consumption of ethanol as inducers of liver cirrhosis

The mechanism(s) of liver damage initiated by ingestion of toxic components of thermally oxidized lipids was compared in a rat model with the documented mechanisms of hepatic failure and necrosis initiated by acetaminophen. Acetaminophen (50 mg/kg body weight) or oxidized lipids (0.15 ml oxidized trilinolein or 1.05 ml oxidized butter oil per rat) were intubated at 12-h intervals to rats. Treated rats were allowed free access to food and water containing 3% ethanol. Changes in relative concentration of acute-phase plasma proteins, determined by two-dimensional (2D) immunoelectrophoresis, were taken as a marker of liver damage. In contrast to simple inflammation, acute-phase plasma proteins in this study disproportionately increased or decreased as histological damage of the liver due to intubation oxidized lipids or acetaminophen. Histological examination of liver of rats intoxicated with oxidized lipids revealed severe liver cirrhosis at the end of the trial, where the remaining viable hepatocytes were separated in a matrix of collagen. [3H1]Thymidine incorporation in hepatic DNA of acetaminophen or oxidized lipid intoxication increased in the early stages of intoxication, indicative of regenerative activity of the liver. Further progression of the cirrhosis inhibited continued liver regeneration and [3H1]thymidine incorporation into hepatic DNA. The cirrhotic liver at this stage failed to regenerate to the original mass upon 75% partial hepatectomy. Therefore, it may be concluded that hepatic necrosis produced by oxidized lipids or by acetaminophen may have similar mechanisms.

Abnormal serum transaminases following therapeutic doses of acetaminophen in the absence of known risk factors

J.M., a healthy, 25-year-old male, volunteered for a study involving warfarin and acetaminophen. Acetaminophen 1 g four times a day was started for 21 days. Liver function tests taken at regular intervals for the first 12 days were unremarkable. On day 18, however, aspartate aminotransferase (AST) was 527 IU/liter and alanine aminotransferase (ALT) was 166 IU/liter. Acetaminophen was discontinued and serum transaminase levels returned to baseline levels two weeks later (AST = 26, ALT = 20). Analysis of J.M.'s urine samples over the first 18 days showed excretion patterns of glucuronide, sulfate, and glutathione derived cysteine and mercapturic acid conjugates were similar to the other subjects in the study. Acetaminophen causes hepatotoxicity in overdose or malnourished or alcoholic patients, none of which applied to our subject. Differences in metabolic activation and capacity for glutathione synthesis can predispose individuals given therapeutic doses of acetaminophen to adverse effects. Failure to detoxify a highly reactive metabolite, formed by P-450 metabolism, via glutathione conjugation is responsible for the development of acute hepatic necrosis. Accumulation of the toxic metabolite due to depleted glutathione stores may have occurred with prolonged high dosing in our subject and been responsible for his abnormal rise in liver enzymes.