Chronic excessive acetaminophen use and liver damage

The Evolution of Circulating Biomarkers for Use in Acetaminophen/Paracetamol-Induced Liver Injury in Humans: A Scoping Review

Acetaminophen (APAP) is a widely used drug, but overdose can cause severe acute liver injury. The first reports of APAP hepatotoxicity in humans were published in 1966, shortly after the development of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as the first biomarkers of liver injury as opposed to liver function. Thus, the field of liver injury biomarkers has evolved alongside the growth in APAP hepatotoxicity incidence. Numerous biomarkers have been proposed for use in the management of APAP overdose patients in the intervening years. Here, we comprehensively review the development of these markers from the 1960s to the present day and briefly discuss possible future directions.

Reduction of systemic exposure and side effects by intra-articular injection of anti-inflammatory agents for osteoarthritis: what is the safer strategy?

Osteoarthritis (OA) is a chronic degenerative joint disease associated with pain, inflammation, and cartilage degradation. However, no current treatment can effectively halt the progression of the disease. Therefore, the use of NSAIDs and intra-articular corticosteroids is usually recommended as the primary treatment for OA-associated pain and inflammation. However, there is accumulating evidence that the long-term use of oral NSAIDs and intra-articular corticosteroids can lead to a myriad of negative side effects. Although numerous efforts have been made to develop intra-articular formulations for NSAIDs, the systemic exposure of intra-articular injection of NSAIDs and its potential side effects have not been explicitly investigated. To ascertain the evident and potential side effects of intra-articular injection of anti-inflammatory agents, we have summarised in this review the systemic exposure, local side effects, and systemic side effects of intra-articular injections of anti-inflammatory agents, including NSAIDs and corticosteroids. For developing a safer treatment to fulfil the unmet long-term use needs of patients, a new therapy, which combines the locally active drug and a sustained-release formulation, has been proposed in this review.

Long-Term Ingestion of Paracetamol and Liver Disease1

Of 45 patients with chronic active hepatitis, 17 had taken paracetamol before the onset of symptoms. There were no significant differences, however, between the two groups in abnormalities of liver function tests, nor in ease of control after paracetamol withdrawal and institution of immunosuppressive therapy. The patient who had taken more than 5 g/week was studied in greater detail, but after a challenge dose of 1 g paracetamol there was no rise in serum aminotransferases and the pattern of excretion of paracetamol metabolites was normal. A critical review of the previously published reports failed to uncover any convincing evidence that paracetamol is an initiating factor in the development of chronic active hepatitis, although it may, at therapeutic levels, cause a toxic hepatitis in those individuals at risk.

Natural product andrographolide alleviated APAP-induced liver fibrosis by activating Nrf2 antioxidant pathway

As a well-known analgesic drug, acetaminophen (APAP) is commonly used to relieve pain for patients with chronic painful diseases. Our previous study has shown that long-term ingestion of APAP caused liver fibrosis in mice. This study further investigated the critical role of nuclear factor erythroid 2-related factor 2 (Nrf2) in regulating APAP-induced liver fibrosis in mice and the anti-fibrotic effect of natural compound andrographolide (Andro). Our results showed that hepatic collagen deposition and hepatic stellate cells (HSCs) activation induced by APAP were more serious in Nrf2 knock-out mice than in normal wild-type mice. Andro reduced HSCs activation in vitro, and also decreased hepatic collagen deposition and HSCs activation induced by APAP in mice. Andro alleviated liver oxidative stress injury induced by APAP in mice and reduced cellular formation of reactive oxygen species (ROS) in HSCs. Andro enhanced Nrf2 nuclear translocation and increased the expression of Nrf2 downstream antioxidant genes both in vitro and in vivo. Furthermore, the Andro-provided protection against APAP-induced liver fibrosis was diminished in Nrf2 knock-out mice. In summary, Nrf2 is critically involved in preventing liver fibrosis induced by long-term administration of APAP in mice, and Andro alleviates APAP-induced liver fibrosis by attenuating liver oxidative stress injury via inducing Nrf2 activation. This study points out the potential application of Andro in the treatment of liver fibrosis in clinic.

Long-term acetaminophen treatment induced liver fibrosis in mice and the involvement of Egr-1

Acetaminophen (APAP)-induced acute liver injury has already been well studied. However, whether long-term administration of APAP will cause liver fibrosis is still not very clear. This study aims to investigate the liver fibrosis in mice induced by long-term APAP treatment and the involvement of early growth response 1 (Egr-1). C57BL/6 mice were orally given with APAP (200, 300mg/kg) for 2, 6 or 10 weeks, respectively. Liver hydroxyproline content, collagen deposition and inflammatory cells infiltration were increased in mice treated with APAP (200, 300mg/kg) for 6 or 10 weeks. Liver mRNA expression of collagen (COL)1a1, Col3a1, transforming growth factor-β (TGF-β) and serum contents of COL1, COL3, TGF-β were all increased in APAP-treated mice. Liver expression of α-smooth muscle actin (α-SMA) and phosphorylated ERK1/2 and Smad2/3 were all increased in APAP-treated mice. Furthermore, increased liver mRNA expression of Egr-1 and its subsequent nuclear translocation were found in APAP-treated mice. Egr-1 knock-out mice were further applied. APAP-induced liver fibrosis was found to be more serious in Egr-1 knock-out mice. N-acetyl-p-benzoquinoneimine (NAPQI), the APAP hepatotoxic metabolite, increased cellular mRNA expression of α-SMA, Col1a1, Col3a1, TGF-β, induced ERK1/2 and Smad2/3 phosphorylation and Egr-1 nuclear translocation in hepatic stellate LX2 cells. In conclusion, long-term administration of APAP induced liver fibrosis in mice, and Egr-1 was critically involved in this process. This study points out a warning and reference for patients with long-term APAP ingestion in clinic.

Abuse liability of centrally acting non-opioid analgesics and muscle relaxants--a brief update based on a comparison of pharmacovigilance data and evidence from the literature

There is a lack of data regarding the abuse liability of centrally acting non-opioid analgesics (NOA) and muscle relaxants (MR). A comparison of data retrieved from a German pharmacovigilance database (BfArM; accessed May 2013) and data from the literature concerning the abuse liability of NOA and MR approved in Germany was performed. The BfArM-database demonstrated cases of abuse only for clonidine and paracetamol, whereas the literature suggests evidence for an abuse potential of baclofen, clonidine, ketamine, metamizole, methocarbamol, orphenadrine, paracetamol, propyphenazone, and tizanidine. The low number of detected cases in the BfArM-database could be a result of under-reporting.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

A review of the hepatotoxicity of paracetamol at therapeutic or near-therapeutic dose levels, with particular reference to alcohol abusers

The number of published reports associating hepatotoxicity with paracetamol ingestion at therapeutic or near-therapeutic dose levels is small but is, nevertheless, suggestive of a relationship. There is however, mounting evidence that certain groups of patients, such as alcohol-dependent people, patients receiving enzyme-inducing drugs (particularly anti-convulsant and anti-tuberculosis medications) as well as those with certain infectious diseases, are rendered more susceptible to paracetamol-induced hepatotoxicity. Seventy-four case reports where therapeutic or near-therapeutic doses of paracetamol resulted in hepatic injury are reviewed and factors and mechanisms which might explain this apparently increased vulnerability to damage are discussed.

Paracetamol (acetaminophen) clearance in patients with cirrhosis of the liver

The pharmacokinetics of paracetamol were studied in 11 patients with cirrhosis of the liver and 12 controls. The average biological half-life after oral administration of 1 g paracetamol was significantly prolonged in patients with hepatic cirrhosis compared to the controls (3.7 hr vs.2.1 hr) and, correspondingly, the average plasma clearance was significantly reduced from 337 ml x min-1 in the controls to 162 ml x min-1 in the patients with cirrhosis of the liver. After subchronic dosing of paracetamol with 1 g paracetamol t. i. d. the plasma half-lives of paracetamol remained unchanged. Steady-state levels of paracetamol were significantly increased in the patients with cirrhosis of the liver. A significant correlation between the values of plasma clearance of paracetamol and prothrombin time (r = +0.88), galactose elimination capacity (r = +0.66), plasma albumin (r = +0.85) was found. No clinical or biochemical signs of hepatotoxicity were observed during the study.

Clinical policy: critical issues in the management of patients presenting to the emergency department with acetaminophen overdose

This clinical policy focuses on critical issues concerning the management of patients presenting to the emergency department (ED) with acetaminophen overdose. The subcommittee reviewed the medical literature relevant to the questions posed. The critical questions are: 1. What are the indications for N-acetylcysteine (NAC) in the acetaminophen overdose patient with a known time of acute ingestion who can be risk stratified by th Rumack-Matthew nomogram? 2. What are the indications for NAC in the acetaminophen overdose patient who cannot be risk stratified by the Rumack-Matthew nomogram? Recommendations are provided on the basis of the strength of evidence of the literature. Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies that are based on preliminary, inconclusive, or conflicting evidence, or based on committee consensus. This guideline is intended for physicians working in EDs.

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.

Clinical policy: critical issues in the management of patients presenting to the emergency department with acetaminophen overdose

This clinical policy focuses on critical issues concerning the management of patients presenting to the emergency department (ED) with acetaminophen overdose. The subcommittee reviewed the medical literature relevant to the questions posed. The critical questions are: 1. What are the indications for N-acetylcysteine (NAC) in the acetaminophen overdose patient with a known time of acute ingestion who can be risk stratified by the Rumack-Matthew nomogram? 2. What are the indications for NAC in the acetaminophen overdose patient who cannot be risk stratified by the Rumack-Matthew nomogram? Recommendations are provided on the basis of the strength of evidence of the literature. Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies that are based on preliminary, inconclusive, or conflicting evidence, or based on committee consensus. This guideline is intended for physicians working in EDs.

Diclofenac potassium 12.5mg tablets for mild to moderate pain and fever: a review of its pharmacology, clinical efficacy and safety

Non-prescription (over-the-counter [OTC]) analgesics are used for the short-term treatment of acute painful conditions of mild to moderate intensity in everyday life. Well documented safety and efficacy, a rapid onset of action and a flexible daily dosing regimen are essential in this context. Film-coated, immediate-release, low-dose diclofenac potassium, developed for OTC use, offers a flexible daily dosing regimen with an initial dose of two tablets (2 x 12.5mg) followed by one or two tablets up to a maximum daily dose of six tablets (75 mg/day). The maximum plasma drug concentration is reached 30 minutes after administration, and the mean terminal half-life is 1-2 hours, allowing a 4- to 6-hour duration of activity, depending on the condition. Thirteen randomised, double-blind trials with both placebo and active controls have demonstrated the efficacy of diclofenac potassium 12.5mg tablets in conditions suitable for treatment with OTC medication, for example, acute lower back pain, headache, acute pain after dental extraction, symptoms of cold and influenza (including fever), and dysmenorrhoea. A single dose of diclofenac potassium 12.5mg is the lowest recommended effective dose. A two-tablet single dose of 25mg is at least as effective as ibuprofen 400mg. A flexible dosing regimen of an initial two tablets followed by one or two tablets up to a total daily dose of 75 mg is as effective as ibuprofen used in comparable fashion up to a total daily dose of 1200 mg. The incidence of adverse events in patients taking single or multiple doses of diclofenac potassium is similar to that of ibuprofen and placebo. In a safety study conducted to compare diclofenac potassium with ibuprofen for up to 3 months in patients with osteoarthritis of the knee, no differences in the pattern of adverse events were noted. There was no evidence of either hepatic injury or cardiovascular safety-related issues at any time during the study. Patients are generally capable of taking diclofenac potassium appropriately. A maximum OTC treatment duration of 5 days for pain and 3 days for fever is recommended.

Paracetamol: new vistas of an old drug

Paracetamol (acetaminophen) is one of the most popular and widely used drugs for the treatment of pain and fever. It occupies a unique position among analgesic drugs. Unlike NSAIDs it is almost unanimously considered to have no antiinflammatory activity and does not produce gastrointestinal damage or untoward cardiorenal effects. Unlike opiates it is almost ineffective in intense pain and has no depressant effect on respiration. Although paracetamol has been used clinically for more than a century, its mode of action has been a mystery until about one year ago, when two independent groups (Zygmunt and colleagues and Bertolini and colleagues) produced experimental data unequivocally demonstrating that the analgesic effect of paracetamol is due to the indirect activation of cannabinoid CB(1) receptors. In brain and spinal cord, paracetamol, following deacetylation to its primary amine (p-aminophenol), is conjugated with arachidonic acid to form N-arachidonoylphenolamine, a compound already known (AM404) as an endogenous cannabinoid. The involved enzyme is fatty acid amide hydrolase. N-arachidonoylphenolamine is an agonist at TRPV1 receptors and an inhibitor of cellular anandamide uptake, which leads to increased levels of endogenous cannabinoids; moreover, it inhibits cyclooxygenases in the brain, albeit at concentrations that are probably not attainable with analgesic doses of paracetamol. CB(1) receptor antagonist, at a dose level that completely prevents the analgesic activity of a selective CB(1) receptor agonist, completely prevents the analgesic activity of paracetamol. Thus, paracetamol acts as a pro-drug, the active one being a cannabinoid. These findings finally explain the mechanism of action of paracetamol and the peculiarity of its effects, including the behavioral ones. Curiously, just when the first CB(1) agonists are being introduced for pain treatment, it comes out that an indirect cannabino-mimetic had been extensively used (and sometimes overused) for more than a century.

Acetaminophen Overuse in the Ohio Medicaid Population

OBJECTIVE

To examine patterns of use of acetaminophen in patients with and without risk factors for hepatotoxicity in the Ohio Medicaid population.

DESIGN

Retrospective, cross-sectional analysis of claims data.

SETTING

Ohio.

PATIENTS

Ohio Medicaid patients (n = 22,496) who received at least 6 prescriptions for acetaminophen from November 1998 through April 1999.

MAIN OUTCOME MEASURE

Overuse of acetaminophen, defined as an average daily dose (ADD) greater than or equal to 4 grams/day or an ADD of greater than or equal to 3 grams/day along with diagnosis codes suggesting underlying liver dysfunction.

RESULTS

We identified 687 patients (3.05%) who received either greater than or equal to 4 grams/day or greater than or equal to 3 grams/day and had diagnosis codes suggesting underlying liver dysfunction (n = 128).

CONCLUSION

Although the number is relatively small, some Ohio Medicaid patients are receiving acetaminophen doses that exceed safety recommendations. Because acetaminophen overuse is the leading cause of liver failure, health care professionals should be alert to the possibility of acetaminophen overuse.

Chronic acetaminophen toxicity: a case report and review of the literature

Acetaminophen is one of the most frequently used medications in the United States. While usual dosing of acetaminophen is considered harmless, both acute and chronic overdoses can be fatal. The majority of reported cases of chronic acetaminophen toxicity in adults occur in chronic alcohol abusers, patients taking P450-inducing medications, or following massive dosing. We describe a case of toxic hepatitis free of the aforementioned risk factors associated with chronic ingestion of moderately excessive doses of acetaminophen. Our patient ingested approximately 5.0 to 6.5 g of acetaminophen daily for 6 to 8 weeks via multiple medications. The inclusion of acetaminophen in numerous medications combined with the frequency of use of acetaminophen necessitates an increased concern for not only acute but also chronic acetaminophen toxicity.

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.

Hepatotoxicity associated with chronic acetaminophen administration in patients without risk factors

OBJECTIVE

To evaluate the literature regarding the potential of acetaminophen to cause toxicity in adult patients without risk factors, when used chronically in daily doses < or = 4 g.

DATA SOURCES

Key tertiary literature was reviewed, along with searches of MEDLINE (1966-July 2001). International Pharmaceutical Abstracts (1970-May 2001), and PREMEDLINE (July Week 5, 2001). Key search terms included acetaminophen, paracetamol, toxic hepatitis, hepatotoxicity, liver dysfunction, overdose, drug toxicity, and poisoning.

DATA SYNTHESIS

Most tertiary references state that the maximum daily dose of acetaminophen is 4 g. Patients taking more than this amount, especially those with certain risk factors, are more likely to develop toxicity. However, a few patients may develop toxicity regardless of risk. An evaluation of the literature regarding the toxic potential of acetaminophen when given at doses < or = 4 g/d chronically (> or = 4 d) to adult patients without risk factors was conducted.

CONCLUSIONS

Acetaminophen should be used cautiously on a chronic basis because several case reports show that it may be hepatotoxic at therapeutic doses.

Potentiation of the immunotoxicity of ethanol by acetaminophen in mice

To investigate the influences of acetaminophen (APP) on the immunotoxicity of ethanol (EtOH) in ICR mice, APP at a dose of 100 mg/kg was orally administered to mice daily for 28 consecutive days. Mice treated with EtOH were given freely with 20% w/v EtOH during the experimental period, and normal mice were given vehicle. The results of this study are summarized as follows: the combination of APP and EtOH significantly decreased the circulating leukocytes and the relative weights of liver, spleen and thymus, compared with the treatment of EtOH alone. In mice receiving the combination of AAP and EtOH when compared with the treatment of EtOH alone, there were also significant reductions in the splenic plaque forming cells (PFC) and hemagglutination (HA) titers to sheep red blood cells (SRBC), and the secondary IgG antibody response to bovine serum albumin (BSA). A tendency toward suppression of delayed-type hypersensitivity (DTH) reaction and phagocytic activity was also observed in the combination of AAP and EtOH. In addition, the combination of AAP and EtOH greatly increased serum alanine aminotransaminase (ALT) and total protein levels, compared with the treatment of EtOH alone. Significant decreases in serum albumin and A/G ratio were observed in EtOH alone-fed mice compared with those in normal animals, and their reductions were further induced in mice treated with AAP and EtOH. These findings indicate that EtOH-induced immunotoxicity is aggravated by the combination of APP and EtOH.

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.

Paracetamol poisoning in children

Paracetamol (acetaminophen) has become an antipyretic drug of choice. Due to its widespread use, toxicity secondary to overdose has increased in recent years. Children are especially vulnerable to accidental exposure due to non availability of child proof containers in India. The main clinical features of acute toxicity include anorexia, vomiting, abdominal pain, jaundice, hematuria and metabolic acidoses. Diagnosis is based on history and laboratory findings of acidosis and abnormal liver function tests. N-acetylcysteine is the specific antidote. This article reviews in detail the toxicokinetics, pathophysiology, clinical features and management of paracetamol poisoning in children.

Standards of laboratory practice: analgesic drug monitoring

Analgesics are the most commonly consumed over-the-counter preparations in the United States. They are used in the treatment of various pain syndromes and other medical conditions. Although analgesics are generally perceived to be safe agents, serious toxicity may occur in the setting of acute overdose, chronic abuse, or overuse. The indications for therapeutic drug monitoring in patients using these medications appropriately is as yet not well defined. The emphasis of this discussion, therefore, is on recommendations for monitoring in situations where toxicity is suspected. Preanalytical, analytical, and practice issues including drug interactions, frequency of monitoring, pertinent ancillary tests, reporting, and special patient groups at risk for toxicity are reviewed. Recent information from a major manufacturer of evacuated tubes arguing against the use of gel tubes for blood collection for drug monitoring is included. Colorimetric/enzymatic/immunoassays for the routine/stat monitoring of acetaminophen and salicylate and diflunisal cross-reactivity with most of the currently used salicylate assays are presented. Achiral and chiral chromatographic assays and newly introduced columns such as restricted access media and/or automated chromatographic systems are reviewed for the analysis of ibuprofen, naproxen, and the recently introduced tramadol. Finally, concepts regarding future directions including drug chirality and chiral analysis are presented.

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.

Cancer Pain Management in Ambulatory Patients

Pain, by definition, is a subjective phenomenon. The subjective component in chronic pain due to cancer is very important. Opioid analgesics are the mainstay of treatment for cancer pain. Their use should be optimized to provide adequate pain relief. Optimal use includes understanding the concepts of tolerance, physical dependence, and psychological dependence. None of these should limit or inhibit pain management. Optimal use also includes familiarity with the clinical use of opioids. Regular use is generally preferred over “prn” use. Increased parenteral versus oral effectiveness of opioids, secondary to a high first-pass effect, is an important consideration when routes of administration must be altered. Familiarity with approximate equianalgesic doses allows for conversion from one opioid to another. Such conversion might help increase the convenience, increase the efficacy, or decrease the adverse effects of an opioid regimen. Knowledge of durations of action of opioids helps in the selection of dosing intervals to facilitate continuous pain relief. Morphine is the most common opioid chosen for cancer pain management, but others may be equally effective. Follow-up assessments with subsequent alterations are as important as the initial selection of drug, dose, and dosing interval. Adjuvant analgesics, such as nonsteroidal antiinflammatory drugs, anticonvulsants, or antidepressants, may enhance pain relief, especially in certain pain syndromes (eg, metastatic bone pain, neuropathic pain). These agents are usually used in addition to opioids.

Metabolic basis for high paracetamol dosage without hepatic injury: a case study

1. Studies of paracetamol metabolism were performed in a 58-year-old female with rheumatoid arthritis who had consumed 15-20 g paracetamol daily for 5 years without developing liver damage and data were compared with results in seven normal volunteers. 2. After a test dose of 2 g paracetamol, the formation of paracetamol sulphate and glucuronide conjugates detected in plasma from the patient was delayed by around 2 h relative to values in normal volunteers and the proportion of sulphate conjugates excreted in urine was 1.5 to 2 times those in normal volunteers (52% vs 26-35% of dose, respectively). The fractional metabolite clearance of paracetamol to glutathione-derived conjugates (0.28 ml min-1 kg-1) in our patient was > 30% lower than in normal females. 3. A combination of slow paracetamol absorption, enhanced detoxication of paracetamol (by sulphation) and reduced metabolism to potentially cytotoxic metabolites may have reduced the risk of liver damage in this patient. The latter may have reflected pharmacogenetic deficiencies in cytochrome P450 isoenzymes persisting despite chronic alcohol consumption (40-60 g per day) or resulted from inhibition of paracetamol activation by concomitant ingestion of aminophylline.

Paracetamol (acetaminophen) poisoning

Paracetamol poisoning caused by intentional overdose remains a common cause of morbidity. In this article the mechanism of toxicity and the clinical effects and treatment of poisoning, including specific antidotal therapy, are reviewed. Areas for further research directed at reducing morbidity and mortality from paracetamol poisoning are considered.

The effect of therapeutic doses of paracetamol on liver function in the rat perfused liver

The isolated liver perfusion technique was used to study the effect of therapeutic doses of paracetamol on hepatic gluconeogenesis and bromosulphthalein clearance from the perfusate and biliary excretion of the dye in the rat. Six groups of rats were studied; those in the three experimental groups were given 0.02 g kg-1 paracetamol daily for ninety days. The livers of animals in the control group and in one of the experimental groups were perfused with a medium containing pyruvate. The animals in the second experimental and control group were perfused with a medium containing bromosulphthalein (10 mg/100 mL). The livers of the third experimental and control group were subjected to histological examination. The rate of glucose formation and glucose concentrations were decreased, while, lactate levels and lactate: pyruvate ratios were increased in paracetamol-treated rats. The mean concentration of bromosulphthalein in the perfusate and biliary excretion of the dye were decreased. Macro and micro vesicular fatty change was present in the livers of paracetamol-treated rats. This study demonstrates that chronic administration of therapeutic doses of paracetamol to rats adversely affects liver function, as evidenced by impaired gluconeogenesis and bromosulphthalein clearance from the perfusate, and excretion of the dye into the bile, and provides histological evidence of hepatic damage in rats.

Drug-induced hepatic injury: an analysis of 1100 cases reported to the Danish Committee on Adverse Drug Reactions between 1978 and 1987

The Danish Committee on Adverse Drug Reactions received 1100 reports of suspected drug-induced hepatic injury during the decade 1978-1987. The causal relationship between drug and hepatic injury was classified as definite in 57 (5.2%) reports, probable in 989 (89.9%) reports, possible in 50 (4.5%) reports and unclassifiable in four (0.4%) reports. Hepatic injuries accounted for 5.9% of all adverse drug reactions reported, and 14.7% of the lethal adverse drug reactions. A total of 47.2% were classified as acute cytotoxic, 16.2% as acute cholestatic and 26.9% as abnormal hepatic function. In 52 (4.7%) cases the hepatic injury was lethal; only 14 (1.3%) cases were chronic. Halothane accounted for 25% of the cases. The incidence of halothane-induced hepatic injury is decreasing, and only one lethal case has been reported since 1981. Next to halothane, sulfasalazine was the drug most often suspected during the last 2 years of the decade. Based on consumption data, the incidence of hepatic injury due to sulindac was estimated to be 18-fold higher than that due to ibuprofen. Paracetamol was reported to induce acute cytotoxic as well as cholestatic reactions in non-alcoholic subjects taking therapeutic doses.

Fulminant hepatic failure possibly related to ciprofloxacin

OBJECTIVE

To report a case of hepatic failure in a patient who was receiving oral ciprofloxacin.

DATA SOURCES

Case reports, review articles, and relevant laboratory studies identified by MEDLINE.

DATA EXTRACTION

Data were abstracted from pertinent published sources by one author and reviewed by the remaining authors.

DATA SYNTHESIS

A 66-year-old man was admitted for hip arthroplasty and developed fulminant hepatic failure during oral ciprofloxacin therapy. Ciprofloxacin was started on postoperative day 13 for treatment of a urinary tract infection. Over the next three days he became confused and hypoglycemic. His prothrombin time increased to greater than 90 s. Serum aspartate aminotransferase and alanine aminotransferase concentrations were markedly elevated. The patient died on postoperative day 20. Postmortem examination of the liver revealed extensive centrilobular necrosis. A skin biopsy was consistent with a drug reaction. It is unknown whether the patient had received a quinolone compound in the past or had a history of exposure to hepatotoxins.

CONCLUSIONS

It cannot be concluded that ciprofloxacin directly caused hepatic failure in this patient. It is possible that the drug evoked a hypersensitivity reaction or exacerbated a preexisting hepatotoxicity. A detailed patient history and evaluation of hepatic function should be obtained prior to initiating ciprofloxacin therapy. A nonquinolone antimicrobial may be a safer alternative for patients with hepatic dysfunction.

Hepatotoxicity due to repeated intake of low doses of paracetamol

The cases of two patients with fulminant hepatic failure after intake of therapeutic doses (4-8 g) of paracetamol, and who were admitted to hospital for assessment for liver transplantation, are described. In both patients starvation, due to abdominal pain, nausea and vomiting or diarrhoea, was probably contributing to the toxic effect of the drug. One of the patients also had an excessive alcohol intake. Paracetamol should not be prescribed for patients with alcoholism or with low food intake.

Alcohol, liver, and nutrition

Until two decades ago, dietary deficiencies were considered to be the major reason why alcoholics developed liver disease. As the overall nutrition of the population improved, more emphasis was placed on secondary malnutrition. Direct hepatotoxic effects of ethanol were also established, some of which were linked to redox changes produced by reduced nicotinamide adenine dinucleotide (NADH) generated via the alcohol dehydrogenase (ADH) pathway. It was also determined that ethanol can be oxidized by a microsomal ethanol oxidizing system (MEOS) involving cytochrome P-450: the newly discovered ethanol-inducible cytochrome P-450 (P-450IIE1) contributes to ethanol metabolism, tolerance, energy wastage (with associated weight loss), and the selective hepatic perivenular toxicity of various xenobiotics. P-450 induction also explains depletion (and enhanced toxicity) of nutritional factors such as vitamin A. Even at the early fatty-liver stage, alcoholics commonly have a very low hepatic concentration of vitamin A. Ethanol administration in animals was found to depress hepatic levels of vitamin A, even when administered with diets containing large amounts of the vitamin, reflecting, in part, accelerated microsomal degradation through newly discovered microsomal pathways of retinol metabolism, inducible by either ethanol or drug administration. The hepatic depletion of vitamin A was strikingly exacerbated when ethanol and other drugs were given together, mimicking a common clinical occurrence. Hepatic retinoid depletion was found to be associated with lysosomal lesions and decreased detoxification of chemical carcinogens. To alleviate these adverse effects, as well as to correct problems of night blindness and sexual inadequacies, the alcoholic patient should be provided with vitamin A supplementation. Such therapy, however, is complicated by the fact that in excessive amounts vitamin A is hepatotoxic, an effect exacerbated by long-term ethanol consumption. This results in striking morphologic and functional alterations of the mitochondria with leakage of mitochondrial enzymes, hepatic necrosis, and fibrosis. Thus, treatment with vitamin A and other nutritional factors (such as proteins) is beneficial but must take into account a narrowed therapeutic window in alcoholics who have increased needs for such nutrients, but also display an enhanced susceptibility to their adverse effects. Massive doses of choline also exerted some toxic effects and failed to prevent the development of alcoholic cirrhosis. Acetaldehyde (the metabolite produced from ethanol by either ADH or MEOS) impairs hepatic oxygen utilization and forms protein adducts, resulting in antibody production, enzyme inactivation, and decreased DNA repair. It also enhances pyridoxine and perhaps folate degradation and stimulates collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of chronic paracetamol administration to rats on the glycosaminoglycan content of patellar cartilage

Male Wistar rats were treated with paracetamol (200 mg/kg twice a day) for 2, 3, 4 and 9 weeks. During the first four weeks of paracetamol administration the serum sulfate concentration was significantly decreased. However, during the fourth until the ninth week, the serum sulfate concentration was only diminished to a small and insignificant extent. The paracetamol administration did not lead to serious liver or renal toxicity, as determined by alanine aminotransferase and creatinine levels in the serum of the rats. The paracetamol-induced serum sulfate depletion, observed during the first four weeks of the experiment, led to a significantly lower glycosaminoglycan content of the patellar cartilage of the rats after three and four weeks paracetamol treatment. When after the fourth week the serum sulfate concentration rose to nearly normal levels also the glycosaminoglycan content in the rat patellar cartilage reached control levels. These data indicate that the serum sulfate depletion might be the causative factor for the observed reduction in glycosaminoglycan content of rat patellar cartilage.

Renal tubular cell or hepatocyte hyperplasia is not associated with tumor promotion by di(2-ethylhexyl)phthalate in B6C3F1 mice after transplacental initiation with N-nitrosoethylurea

B6C3F1 mice of both sexes that had been exposed transplacentally on day 18 of gestation to 0.5 mmole N-nitrosoethylurea (NEU) were fed either normal diets or diets containing di(2-ethylhexyl)phthalate (DEHP) at 6,000 ppm beginning at 6 wk of age and continuing to 78 wk of age. At 52 and 78 wk of age, 6-26 mice from each group received a single injection of 5-bromo-2'-deoxyuridine (Brdu) at 200 mg/kg i.p. and were sacrificed 1 h later for determination of the levels of renal and hepatic DNA synthesis by the Brdu immunohistochemical technique. No differences occurred in incidences of gross or microscopic renal tubular cell tumors between the NEU (males 15%, females 21%) and NEU-DEHP groups (males 10%, females 15%) at 78 wk. The labelling index (LI) of renal cortical tubular cells was significantly increased at 78 wk (22.3 +/- 3.7/mm2 for males, 21.8 +/- 1.2 for females) in mice given NEU and DEHP as compared with NEU alone (9.7 +/- 1.0 for males, 6.9 +/- 0.7 for females). The number and sizes of focal hepatocellular proliferative lesions (FHPL), including hyperplastic foci, hepatocellular adenomas and carcinomas, were quantified by image analysis and stereology. DEHP significantly enhanced the mean volume and volume % of FHPL, including liver tumors, but not numbers of FHPL/liver. Hepatocyte LI was also not affected, at least as detected by the technique used, while FHPL had significantly increased LI (14.5-48.3) as compared with normal hepatocytes (0.5-2.4). This study provides some evidence that enhanced chronic cell replication in the kidney may not always be associated with renal carcinogenesis of tumor promotion, while tumor promotion in liver may be a consequence of increased DNA synthesis in initiated or focus cells rather than in nonproliferative parenchymal hepatocytes, which may not be target cells of some tumor promoters.

Mechanism of ethanol induced hepatic injury

Ethanol is hepatotoxic through redox changes produced by the NADH generated in its oxidation via the alcohol dehydrogenase pathway, which in turn affects the metabolism of lipids, carbohydrates, proteins and purines. Ethanol is also oxidized in liver microsomes by an ethanol-inducible cytochrome P-450 (P-450IIE1) which contributes to ethanol metabolism and tolerance, and activates xenobiotics to toxic radicals thereby explaining increased vulnerability of the heavy drinker to industrial solvents, anesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens and even nutritional factors such as vitamin A. Induction also results in energy wastage and increased production of acetaldehyde. Acetaldehyde, in turn, causes injury through the formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, and alterations in microtubules, plasma membranes and mitochondria with a striking impairment of oxygen utilization. Acetaldehyde also causes glutathione depletion and lipid peroxidation, and stimulates hepatic collagen synthesis, thereby promoting fibrosis.

Effects of sulfur-amino acid-deficient diets on acetaminophen metabolism and hepatotoxicity in rats

Cysteine is required for the synthesis of cosubstrates for two pathways of acetaminophen metabolism: 3'-phosphoadenosine-5'-phosphosulfate (PAPS) for sulfation and glutathione (GSH) for detoxification of the reactive metabolite (N-acetyl-p-benzoquinoneimine, NAPQI). Dietary deficiency of cysteine may reduce hepatic production of PAPS and GSH and thereby reduce metabolism of the drug (by sulfation and detoxification of NAPQI) and hence lead to potentiation of acetaminophen liver injury. Conversely, limitation of sulfur-containing amino acids could result in depression of protein synthesis and hepatic cytochrome P450 levels, and hence in decreased reactive metabolite formation and decreased liver injury. To determine whether the potentiating effects exceed the protective effects, rats were fed isocaloric AIN-76 liquid diets containing various levels of methionine as the sole source of sulfur in the diet for 3 weeks prior to administration of acetaminophen. Sulfur deficiency was assessed by measuring urinary inorganic sulfate levels. Sulfur-deficient diets retarded growth but did not affect nitrogen balance. Sulfur-deficient animals had lower basal levels of hepatic GSH. Pharmacokinetic studies revealed that at low doses of acetaminophen (20 mg/kg), animals fed sulfur-deficient diets metabolized the drug more slowly due to a markedly reduced sulfation capacity, whereas at the high dose of acetaminophen (400 mg/kg), rats that were fed sulfur-deficient diets had a higher clearance of the drug than rats that were fed the complete diet. The increase in clearance was due largely to an enhanced glucuronidation capacity and an enhanced P450-dependent oxidation as indicated by mercapturate formation. Histologic studies revealed that rats fed sulfur-deficient diets showed increases in both incidence and severity of acetaminophen hepatic necrosis. Thus, the potentiating effects exceeded the protective effects. These observations raise the possibility that nutritional inadequacy of sulfur-containing amino acids which could occur during protein malnutrition may similarly enhance susceptibility to acetaminophen liver injury in humans.

Biochemical basis for alcohol-induced liver injury

Chronic ethanol ingestion leads to hepatocellular injury and alcoholic liver disease (ALD) only if multiple factors combine to favor centrilobular hepatocellular hypoxia. It is hypothesized that these factors include a shift in the redox state, the induction of the microsomal ethanol oxidizing system (MEOS), a high blood alcohol level (BAL), a high polyunsaturated fat diet and episodic decreased O2 supply to the liver. The shift in the redox state favors a low cellular pH, decreased fatty acid oxidation and increased triglyceride formation. The increased MEOS activity increases O2 consumption and portal-central O2 gradient as well as favors acetaldehyde toxic effects including retention of hepatic lipids and export proteins causing cell swelling. The resultant increase in the concentration of acetaldehyde and lactate may stimulate fibrosis as they stimulate collagen synthesis in vitro. The resultant fatty liver narrows the sinusoids slowing sinusoid blood flow. The combination of events reduces available O2 leading to decreased levels of ATP and cellular pH making the liver vulnerable to episodes of systemic hypoxia. The role of membrane changes are reviewed, i.e., 1) membrane fluidity as related to changes in the species of phospholipids, 2) mitochondrial function as related to the changes in the lipid environment of the electron transport chain, and 3) linoleic acid-prostaglandin metabolism. Acute ethanol in vitro has been shown to affect liver cell metabolism regulation by triggering and increasing protein phosphorylation through the Ca2+-phospholipase C pathway. A high fat diet enhances the liver injury caused by chronic ethanol ingestion.

The chronic hepatic or renal toxicity of di(2-ethylhexyl) phthalate, acetaminophen, sodium barbital, and phenobarbital in male B6C3F1 mice: autoradiographic, immunohistochemical, and biochemical evidence for levels of DNA synthesis not associated with carcinogenesis or tumor promotion

Male B6C3F1 mice, 6 weeks of age, were fed diets or water containing di(2-ethylhexyl) phthalate (DEHP) at 12,000 or 6000 ppm, acetaminophen (ACT) at 10,000 or 5000 ppm, sodium barbital (BBS) at 1000 ppm, or phenobarbital (PB) at 500 ppm for 40 weeks. Groups of six mice were terminated at 2, 8, 24, and 40 weeks for evaluation of liver and kidney weights, histopathology, and thymidine kinase (TK) activity in liver and kidney and levels of DNA synthesis, measured by tritiated thymidine [( 3H]T) autoradiography or bromodeoxyuridine (BrdU) immunohistochemistry. Liver weights, as percentage of body weight, were significantly elevated at most time intervals for mice exposed to all chemicals at each dose. The hepatocyte labeling indices (LI) with [3H]T autoradiography or BrdU immunocytochemistry were significantly elevated in mice fed DEHP at 12,000 ppm at 24 and 40 weeks or BBS and ACT at 2 weeks. LI were not elevated in mice fed PB. Hepatic TK activity was significantly elevated in mice fed DEHP, BBS, or ACT at Weeks 2 and 8. Histopathologic hepatic lesions were associated with these elevations, while hepatic lesions were not associated with changes in TK activity in PB-treated mice. In contrast, only DEHP and BBS induced toxic renal lesions. Persistent or transient elevation of the renal LI and TK activity accompanied renal toxicity. Thus, the hepatic toxin DEHP induced chronic renal hyperplasia without evidence of renal carcinogenicity or tumor promotion in previous studies at the doses used. ACT, a hepatotoxin, produced transient chronic hepatic hyperplasia without evidence of carcinogenicity in B6C3F1 mice in earlier studies at the same doses used. Thus, persistent or transient hepatic or renal hyperplasia was associated with carcinogenic or tumor promoting activity of these chemicals in some cases but not in others.

Specificity of a colorimetric paracetamol assay technique for use in cases of overdose

A simple, economical colorimetric procedure for the determination of Paracetamol in serum or plasma (50-450 micrograms/ml) is described. Using the described method it is possible to quantify Paracetamol concentrations within 25 min which makes the technique ideal for use in an emergency-suspected overdose situation. A total of 178 drug/drug combination products were examined for possible interference with the method and of these, eight were shown to interfere significantly with the quantitative assay. However, in all cases it would be possible to correct for the interference to arrive at a semi-quantitative value for Paracetamol concentration by using the absorbance and by comparing the visible colour of the test sample with the Paracetamol standards.

Acute and chronic drug-induced hepatitis

Adverse drug reactions may mimic almost any kind of liver disease. Acute hepatitis is often due to the formation of reactive metabolites in the liver. Despite several protective mechanisms (epoxide hydrolases, conjugation with glutathione), this formation may lead to predictable toxic hepatitis after hugh overdoses (e.g. paracetamol), or to idiosyncratic toxic hepatitis after therapeutic doses (e.g. isoniazid). Both genetic factors (e.g. constitutive levels of cytochrome P-450 isoenzymes, or defects in protective mechanisms) and acquired factors (e.g. malnutrition, or chronic intake of alcohol or other microsomal enzyme inducers) may explain the unique susceptibility of some patients. Formation of chemically reactive metabolites may also lead to allergic hepatitis, probably through immunization against plasma membrane protein epitopes modified by the covalent binding of the reactive metabolites. This may be the mechanism for acute hepatitis produced by many drugs (e.g. amineptine, erythromycin derivatives, halothane, imipramine, isaxonine, alpha-methyldopa, tienilic acid, etc.). Genetic defects in several protective mechanisms (e.g. epoxide hydrolase, acetylation) may explain the unique susceptibility of some patients, possibly by increasing exposure to allergenic, metabolite-altered plasma membrane protein epitopes. Like toxic idiosyncratic hepatitis, allergic hepatitis occurs in a few patients only. Unlike toxic hepatitis, allergic hepatitis is frequently associated with fever, rash or other hypersensitivity manifestations; it may be hepatocellular, mixed or cholestatic; it promptly recurs after inadvertent drug rechallenge. Lysosomal phospholipidosis occurs frequently with three antianginal drugs (diethylaminoethoxyhexestrol, amiodarone and perhexiline). These cationic, amphiphilic drugs may form phospholipid-drug complexes within lysosomes. Such complexes resist phospholipases and accumulate within enlarged lysosomes, forming myeloid figures. This phospholipidosis has little clinical importance. In a few patients, however, it is associated with alcoholic-like liver lesions leading to overt liver disease and, at times, cirrhosis. Subjects with a deficiency in a particular isoenzyme of cytochrome P-450 poorly metabolize perhexiline and are at higher risk of developing liver lesions. Prolonged, drug-induced liver-cell necrosis may also lead to subacute hepatitis, chronic hepatitis or even cirrhosis. This usually occurs when the drug administration is continued, either because the liver disease remains undetected or because its drug aetiology is overlooked. Several autoantibodies may be present.(ABSTRACT TRUNCATED AT 400 WORDS)

Subacute acetaminophen overdose after incremental dosing

A case of acetaminophen poisoning following the ingestion of 26 g of acetaminophen by incremental dosing over a 25-h period is reported. At presentation, seven h after the last ingestion, the patient experienced hematemesis, the acetaminophen level was 150 micrograms/mL, and the SGOT was normal. The patient recovered uneventfully following N-acetylcysteine therapy. A review of the pharmacology and toxicity of acetaminophen is discussed. The case illustrates the problems of judging hepatotoxic potential in a multiple-dose acetaminophen ingestion and describes the successful use of N-acetylcysteine in a patient with a "subacute" acetaminophen overdose.

Biochemical changes associated with the potentiation of acetaminophen hepatotoxicity by brief anesthesia with diethyl ether

Acetaminophen hepatotoxicity in male CD-1 mice was enhanced markedly by brief anesthesia with diethyl ether (ether), and particularly so if acetaminophen was given several hours after ether. The present study was conducted to examine the possible biochemical mechanisms behind this delayed toxicologic synergism. In vitro biochemical studies indicated that ether anesthesia produced a delayed reduction in the activities of glucuronyl transferase and glutathione (GSH) S-transferase, and in the hepatic content of GSH. The hepatic content but not activity of the cytochromes P-450 was initially reduced by ether but recovered by the time of maximal toxicologic enhancement. In vivo studies showed that ether produced a small decrease in the plasma concentrations of glucuronide and sulfate conjugates of acetaminophen, with a concomitant, minor increase in the half-life of acetaminophen, and a major increase in the bioactivation of acetaminophen, as determined by an early, 2-fold increase in the plasma GSH and cysteine conjugates of acetaminophen, and a 3-fold increase in the covalent binding of acetaminophen to hepatocellular protein. Decreases produced by ether in the in vivo production of acetaminophen glucuronide correlated with increasing plasma concentrations of unmetabolised acetaminophen, decreasing hepatic GSH content and increasing covalent binding of acetaminophen to hepatocellular protein when these measurements were performed in the same animals. The biochemical mechanisms underlying the potentiation of acetaminophen hepatoxicity as measured by plasma glutamic pyruvic transaminase concentrations appeared to be due to delayed, complex effects of ether upon multiple enzymatic pathways of acetaminophen elimination and detoxification.

Potential role of activated macrophages in acetaminophen hepatotoxicity. I. Isolation and characterization of activated macrophages from rat liver

Twenty-four hours following treatment of rats with the analgesic acetaminophen (1.2 g/kg), we observed an infiltration of mononuclear cells into centrilobular regions of the liver in the absence of necrosis. To determine whether acetaminophen induces the accumulation and activation of mononuclear phagocytes, we compared the morphologic and functional characteristics of macrophages obtained from livers of acetaminophen-treated rats with those of resident macrophages (Kupffer cells) from untreated control animals. Macrophages were isolated from rat livers by combined collagenase/pronase perfusion, selective digestion, and differential centrifugation on a metrizamide gradient. Acetaminophen treatment resulted in a twofold increase in macrophage yields from the liver compared with controls. Macrophages isolated from treated animals were generally larger than resident Kupffer cells, were highly vacuolated, and adhered to culture dishes more rapidly. Liver macrophages from both treated and untreated rats phagocytized sheep red blood cells (sRBC) in a time-dependent manner, reaching a maximum after 60-75 min incubation with sRBCs. However, macrophages from livers of acetaminophen-treated rats phagocytized two to three times more sRBC than did resident Kupffer cells. Using the Boyden chamber technique, both macrophage populations were found to be chemotactic to a number of stimuli including the complement fragment, C5a, and synthetic collagenous peptides related to tissue breakdown products. Levels of migration of macrophages from livers of acetaminophen-treated rats were four to seven times greater than those of resident Kupffer cells. In addition, compared with resident Kupffer cells, macrophages from acetaminophen-treated rats released 30% more superoxide anion in response to the stimulus, 12-O-tetradecanoyl-phorbol-13-acetate. Taken together, these results suggest that acetaminophen treatment of rats leads to the recruitment and activation of macrophages in the liver.

Effects of chronic ethanol feeding on glutathione turnover in the rat

Glutathione (GSH) is important in protection of cells against electrophilic drug injury and against reactive oxygen species. Both steady-state concentrations and turnover of GSH are important determinants of susceptibility of the hepatocyte to injury. Chronic ethanol administration is known to enhance susceptibility to electrophilic drug injury. We have examined the effects of chronic ethanol feeding on GSH turnover and the hepatic activities of GSH peroxidase and enzymes of the gamma-glutamyl cycle in the rat. Turnover of GSH was measured in individual animals by measuring the decrease in specific activity of GSH in bile over time after i.v. administration of [35S]cysteine. Rats fed ethanol had significantly increased rates of GSH turnover, 0.287 +/- 0.050 hr-1 vs 0.131 +/- 0.041 hr-1 (P less than 0.001), as well as steady-state GSH levels, 6.59 +/- 1.55 vs 4.30 +/- 1.28 mumoles/g liver (P less than 0.01). The activities of gamma-glutamyltransferase (GGT) and GSH-synthesizing enzymes were correspondingly increased significantly. By contrast, GSH peroxidase activity was decreased in ethanol-fed rats, 194 +/- 20.8 vs 311 +/- 89.9 nmoles NADPH oxidized/min/mg protein (P less than 0.001). Biliary output and concentrations of GSH and GSSG were similar in both groups. The increase in turnover of GSH was not due to an increase in oxidation of GSH. There was, however, an association between GSH turnover and the activity of hepatic GGT in ethanol-fed but not in control rats.

Protection against paracetamol-induced hepatotoxicity by acetylsalicylic acid in rats

Acetylsalicylic acid (ASA) given simultaneously with paracetamol decreased paracetamol-induced hepatotoxicity (measured by plasma transaminase activities as well as histology) without any effect on glutathione depletion, indicating that ASA prevents a process (or processes) subsequent to the metabolic activation of paracetamol. Delayed treatment with ASA also reduced paracetamol-induced liver toxicity, suggesting that reduction of the absorption rate of paracetamol does not contribute essentially to the protection by ASA. Combinations of paracetamol and ASA may have potential use in the development of safer analgesic combinations containing paracetamol (or ASA).