Drug interactions affecting analgesic toxicity

Vascularized liver-on-a-chip model to investigate nicotine-induced dysfunction

The development of physiologically relevant in vitro systems for simulating disease onset and progression and predicting drug metabolism holds tremendous value in reducing drug discovery time and cost. However, many of these platforms lack accuracy in replicating the tissue architecture and multicellular interactions. By leveraging three-dimensional cell culture, biomimetic soft hydrogels, and engineered stimuli, in vitro models have continued to progress. Nonetheless, the incorporation of the microvasculature has been met with many challenges, specifically with the addition of parenchymal cell types. Here, a systematic approach to investigating the initial seeding density of endothelial cells and its effects on interconnected networks was taken and combined with hepatic spheroids to form a liver-on-a-chip model. Leveraging this system, nicotine's effects on microvasculature and hepatic function were investigated. The findings indicated that nicotine led to interrupted adherens junctions, decreased guanosine triphosphate cyclohydrolase 1 expression, impaired angiogenesis, and lowered barrier function, all key factors in endothelial dysfunction. With the combination of the optimized microvascular networks, a vascularized liver-on-a-chip was formed, providing functional xenobiotic metabolism and synthesis of both albumin and urea. This system provides insight into potential hepatotoxicity caused by various drugs and allows for assessing vascular dysfunction in a high throughput manner.

Effect of excipients on acetaminophen metabolism and its implications for prevention of liver injury

Acetaminophen poisoning is the most frequent cause of acute hepatic failure in the US. Toxicity requires reductive metabolism of acetaminophen, primarily via CYP2E1. Liquid acetaminophen preparations contain propylene glycol, a common excipient that has been shown to reduce hepatocellular injury in vitro and in rodents. Children are less susceptible to acetaminophen toxicity for unclear reasons. We conducted a pharmacokinetic single-blinded crossover study of 15 healthy adult volunteers comparing the CYP2E1 and conjugative metabolism of a 15 mg/kg dose of liquid versus solid preparations of acetaminophen. Measured AUC's for the CYP2E1 metabolites were 16-17% lower and extrapolated AUC's were 25-28% lower in the liquid formulation arm while there was no difference in conjugative metabolite production. The formation rate constants for reductive metabolites were equivalent between solid and liquid formulations indicating that enzyme inhibition was competitive. Propylene glycol, an established CYP2E1 competitive antagonist, was detected in the liquid formulation but not solid formulation arm. Since children tend to ingest liquid preparations, the protective effect of this excipient could explain their decreased susceptibility to acetaminophen toxicity. A less hepatotoxic formulation of acetaminophen could potentially be developed if co-formulated with a CYP2E1 inhibitor.

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.

Severe hepatotoxic adverse reaction in a healthy schoolgirl after treatment with flucloxacillin

This is the first detailed description of a severe hepatotoxic reaction in a previously healthy 9-year-old schoolgirl after ingestion of some flucloxacillin tablets. She was clinically well within one week and alanine aminotransferase in serum was normalized in one month. Follow up for more than one year was normal.

The Therapeutic Use of Acetaminophen in Patients with Liver Disease

Acetaminophen has been used safely and effectively for many years to manage pain and/or fever in patients of all ages. It is commonly recommended as first-line therapy for a variety of patients and conditions, including the elderly, children with viral illnesses, and patients with osteoarthritis, gastrointestinal conditions, bleeding disorders, cardiovascular disease, or renal disease. However, its use is often avoided in patients with chronic liver disease. The perception that acetaminophen should be avoided in such patients arose from awareness of the association between massive acetaminophen overdose and hepatotoxicity, combined with a lack of understanding of the metabolism of acetaminophen in patients with liver disease. There are various theoretical mechanisms of acetaminophen hepatotoxicity in chronic liver disease including: altered metabolism and depleted glutathione stores that would be expected to increase accumulation of the hepatotoxic intermediate, N-acetyl-p-benzoquinone imine (NAPQI). Available studies in patients with chronic liver disease, however, have shown that although the half-life of acetaminophen may be prolonged, cytochrome P-450 activity is not increased and glutathione stores are not depleted to critical levels in those taking recommended doses. Furthermore, acetaminophen has been studied in a variety of liver diseases without evidence of increased risk of hepatotoxicity at currently recommended doses. Therefore, acetaminophen can be used safely in patients with liver disease and is a preferred analgesic/antipyretic because of the absence of the platelet impairment, gastrointestinal toxicity, and nephrotoxicity associated with nonsteroidal antiinflammatory drugs.

The effect of regular medication on the outcome of paracetamol poisoning

BACKGROUND

Patients admitted with paracetamol overdose frequently receive one or more types of regular medication that may affect the outcome of the paracetamol intoxication.

AIM

To describe the use of regular medication in patients with paracetamol poisoning and to evaluate its effects on morbidity and mortality.

METHODS

Seven hundred and thirty-seven consecutive patients admitted with paracetamol poisoning were studied and the use of regular medication was recorded. The relative risk of hepatic encephalopathy, death or liver transplantation, severe hepatic dysfunction and severe hepatocellular injury was evaluated by multivariate analysis.

RESULTS

Regular medication was received by 332 patients (45%). Medication with benzodiazepines (105 cases), antidepressants (100 cases), neuroleptics (75 cases), paracetamol (58 cases), oral contraceptives (51 cases), beta-agonists (40 cases), opioid analgesics (32 cases) and anticonvulsants (27 cases) predominated. Regular medication with opioid analgesics was associated with a high incidence of hepatic dysfunction (odds ratio, 5.39; 95% confidence interval, 1.13-25.8). No significant findings were demonstrated for benzodiazepines, antidepressants, neuroleptics, paracetamol, oral contraceptives, beta-agonists or anticonvulsants in the multivariate analysis.

CONCLUSIONS

Regular medication with psychotropic medication, analgesics, oral contraceptives, beta-agonists or anticonvulsants was frequent in patients admitted with paracetamol poisoning. Medication with opioid analgesics was associated with a significantly increased incidence of hepatic dysfunction, whereas the other medications did not appear to affect the outcome of the paracetamol intoxication.

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.

Early indicators of response in biologically based risk assessment for nongenotoxic carcinogens

The proposed existence of dose-response thresholds for nongenotoxic carcinogens has led to a major controversy in the risk extrapolation process. To resolve this debate, there has been a significant investment in mechanism-based risk assessment research. The ability to utilize this mechanistic research for risk assessment procedures is still limited and may not warrant the expense. Alternatively, an approach can be used to identify dose-response thresholds through the utilization of sensitive indicators of biological response. This approach does not rely upon a mechanistic framework for the development of pathology, is solely dependent on already existing technology, and takes into account the possibility of background levels of pathway activation. For this approach, sensitive biochemical responses need to be identified and linked to the introduction of the toxicant through dose response, by time of response, and, when possible, through a proposed biochemical mechanism. The weakness of this approach is that more sensitive unidentified responses may exist requiring that a safety factor of 10 be used to define a NOEL. For dioxin-like compounds, using a surrogate marker of response CYP1A1 induction, this approach yields an estimate of the acceptable daily intake of 5-50 fg/kg/day. This limit is remarkably similar to the results of the original EPA linear extrapolation (6 fg/kg/day). A similar approach can be used for other nongenotoxic carcinogens and the analysis can be completed within 1 year.

The hepatoprotective effects of Solanum alatum Moench. on acetaminophen-induced hepatotoxicity in mice

Solanum alatum Moench. has been shown to have a protective effect against carbon tetrachloride (CCl4)-induced liver injury. Solanum alatum treatment (100 mg/kg, p.o.) decreased the elevation of serum alanine aminotransferase (ALT; GPT) and aspartate aminotransferase (AST; GOT) induced by acetaminophen (paracetamol) (600 mg/kg, i.p.) administration. It also decreased the extent of visible necrosis in liver tissue. In addition, Solanum alatum treatment restored hepatic glutathione (GSH) depletion induced by acetaminophen (600 mg/kg, i.p.) administration. Microsomal enzyme levels such as P-450, reductase, and aniline hydroxylation enzyme were also restored to normal levels after Solanum alatum administration. The hepatoprotective mechanism may function through direct binding with acetaminophen toxic metabolites, decreasing the attraction of acetaminophen metabolites for other cellular GSH or thiol protein. Additionally, Solanum alatum treatment increased the concentration of hepatic GSH and maintained a high level activity of GSTase, which led to acceleration of the excretion of toxic acetaminophen metabolites.

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.

[Propacetamol: from basic action to clinical utilization]

OBJECTIVE

To review pharmacology and therapeutic use of propacetamol, an injectable prodrug of acetaminophen (paracetamol).

DATA SOURCES

Extraction from the Medline database of French and English articles on pharmacology and clinical use of propacetamol.

STUDY SELECTION

Articles providing new data into the mechanisms of the analgesic action of paracetamol. Selection of controlled studies (original articles and abstracts of oral communications on therapeutic trials with propacetamol as a single agent or part of balanced analgesia protocols). Case reports and letters to the editor were not considered in this analysis.

DATA EXTRACTION

Clinical articles were selected for advantages and adverse effects of propacetamol. Articles dealing with mechanisms of action of propacetamol and paracetamol were selected for the more recent data, excluding those reporting outdated theories not confirmed or abandoned.

DATA SYNTHESIS AND CONCLUSION

Mechanisms of action of paracetamol differ from those of NSAIDs, giving account of a low risk of adverse renal, gastrointestinal and haematological effects. Thanks to their high therapeutic index, prescription of propacetamol and paracetamol is quite simple and safe. Main indications of both drugs are painful conditions, especially but not exclusively in the postoperative period, not requiring opioids and also in combination with other analgesic drug and/or techniques (balanced or multimodal analgesia). Because of cost, IV propacetamol is changed for oral paracetamol as soon as possible.

Comparison of paracetamol-induced hepatotoxicity in the rat in vivo with progression of cell injury in vitro in rat liver slices

The flux in rat hepatic ratio of adenosine triphosphate levels to adenosine diphosphate levels (ATP/ADP) during the onset and progression of paracetamol-induced cell injury both in vivo and in vitro were investigated and compared. Leakage of lactate dehydrogenase (LDH) and potassium (K+), and mg water/mg dry weight quantified cell injury. ATP and ADP levels were determined using the luciferin-luciferase bioluminescence assay. For in vitro studies, liver slices obtained from phenobarbitone-induced rats were exposed to 10 mM paracetamol for 120 min (T0-T120) and, then incubated without paracetamol up to a further 240 min (T120-T360). For in vivo studies, groups of four phenobarbitone-induced rats received i.p. injections of 800 mg/kg paracetamol. ATP/ADP ratios fall upon exposure to paracetamol both in vitro and in vivo. However, unlike the in vitro situation where the fall in ATP/ADP ratios precedes and accompanies the progression of cell injury, the in vivo fall in ATP/ADP ratios is shown to occur as cell injury measurements begin to recover to control levels. However, despite these differences classic paracetamol-induced centrilobular necrosis is observed to occur both in vitro and in vivo. This study demonstrates that the liver slice model is a simple and useful technique to investigate the underlying mechanisms of paracetamol-induced cell injury.

Cimetidine does not alter the clearance or plasma binding of tenidap in healthy male volunteers

1. An open-label, placebo-controlled study was conducted to examine the effect of cimetidine on the steady-state pharmacokinetics of tenidap. 2. Twenty-four healthy volunteers received tenidap sodium (120 mg) each morning throughout the study. On day 14 plasma levels of tenidap had reached steady state; half of the subjects were treated concomitantly with cimetidine 800 mg at night, while the other half received placebo. Allocation of cimetidine or placebo was randomised. Plasma profiles of tenidap were measured on days 14 and 16. 3. The addition of cimetidine did not significantly affect the Cmax, tmax, or lambda z of tenidap. The AUC(0,24h) increased by 4% between days 14 and 16 in the cimetidine treatment group, compared with a decrease of 2% in the placebo group. This small difference is statistically significant (P = 0.047), but it is not considered to be clinically relevant. 4. It is concluded that concomitant administration of cimetidine does not significantly affect the pharmacokinetics of tenidap at steady state.

Increased metabolism of acetaminophen in chronically alcoholic patients

The aim of this work was to determine whether the metabolism of acetaminophen increases in chronic alcoholics, and consequently whether the production of its hepatotoxic metabolite is enhanced. For this purpose, the pharmacokinetics of acetaminophen were compared in 12 alcoholic men and 12 healthy controls. After a 12-hr fast, the patients (on the 3rd hospital day) and volunteers were given 1 g of oral acetaminophen at 8.00 AM. Venous blood samples were drawn before drug intake and at regular intervals after to evaluate plasma acetaminophen concentrations. The elimination half-life of acetaminophen was significantly shorter in the alcoholic patients than in the controls (1.70 +/- 0.55 vs. 2.84 +/- 0.30 hr, p < 0.001). Similarly, total plasma acetaminophen clearance was significantly higher in the patients than in the controls (29.19 +/- 13.37 vs. 24.45 +/- 11.10 l/hr, p < 0.05). These results confirm that the metabolism of acetaminophen increases in chronic alcoholism and consequently suggest that its potential liver toxicity might be enhanced.

Variations of cortisol hydroxylation and paracetamol metabolism in patients with bladder carcinoma

We investigated the possibility that variations of the metabolism of xenobiotic compounds might be involved in the process of bladder carcinogenesis, by studying activation reactions (phase I) and detoxification reactions (phase II) of xenobiotic compounds in a group of patients with transitional cell carcinoma of the bladder and in a group of controls hospitalised with other diseases. As an indirect estimate of activating reactions (phase I) we measured cortisol hydroxylation, expressed as the ratio between urinary 6-beta-OH-cortisol and 17-OH-corticosteroids. Cortisol hydroxylation was not increased in the group of patients when compared with controls. The variations of phase II conjugating enzymes were followed indirectly by administering paracetamol and measuring the urinary excretion of its main metabolites over a period of 12 h. The variations in the metabolic conjugation of paracetamol were expressed as a percentage of each metabolite, or of unmodified paracetamol excreted in the urine, or as the ratio between a given metabolite and unmodified paracetamol. The data were analyzed with a logistic regression model, analysing the effects of possible confounding variables such as age, smoking, alcohol, blood nitrogen, blood creatinine, glutamic-pyruvic (SGPT), glutamic-oxalacetic transaminases (SGOT) and percent recovery of paracetamol in the urine. Statistical analysis showed that the excretion of mercapturate derivatives of paracetamol was significantly increased in the group of patients. The levels of glucuronic, sulphate and cysteine metabolites were not varied significantly. Since mercapturate derivatives are formed as a consequence of the formation of short-lived metabolites of paracetamol which react with protein, nucleic acids or glutathione, the increased excretion of mercapturic acid derivatives in cancer patients might be an indication of a higher capability of forming reactive molecular species from xenobiotic compounds. We suggest that this factor might play a role in the induction of bladder cancer.

Glutathione deficiency in alcoholics: risk factor for paracetamol hepatotoxicity

Patients chronically abusing ethanol are more susceptible to the hepatotoxic effects of paracetamol. This could be due to an increased activation of the drug to a toxic metabolite or to a decreased capacity to detoxify the toxic metabolite by conjugation with glutathione (GSH). To test these hypotheses paracetamol 2 g was administered to five chronic alcoholics without clinical evidence of alcoholic liver disease and five control subjects. The urinary excretion of cysteine- plus N-acetyl-cysteine-paracetamol, the two major products of detoxification of the reactive metabolite of paracetamol, was not significantly higher in chronic alcoholics arguing against a substantially increased metabolic activation of paracetamol. Chronic alcoholics had significantly lower plasma concentrations of GSH than healthy volunteers, however (4.35 (1.89) microM v 8.48 (2.68) microM, p less than 0.05) before the administration of paracetamol, and plasma GSH reached lower concentrations in the alcoholics after paracetamol (2.40 (1.36) v 6.26 (2.96) microM). In a group of patients with alcoholic hepatitis intrahepatic GSH was significantly lower than in patients with chronic persistent hepatitis and patients with non-alcoholic cirrhosis, suggesting that low plasma GSH in alcoholics reflects low hepatic concentrations of GSH. The data indicate that low GSH may be a risk factor for paracetamol hepatotoxicity in alcoholics because a lower dose of paracetamol will be necessary to deplete GSH below the critical threshold concentration where hepatocellular necrosis starts to occur.

Urinary 6-beta-OH-cortisol and paracetamol metabolites as a probe for assessing oxidation and conjugation of chemicals in humans

The ratio between urinary 6-beta-OH-cortisol and 17-OH-corticosteroids was taken as an indirect estimate of monoxygenase activity in a population of controls and epileptic patients undergoing therapy with diphenylhydantoin and phenobarbital. Cortisol hydroxylation was increased in the group of epileptics with large inter-individual variations notwithstanding a similar dosage of inducers. The levels of some phase II conjugating enzymes were followed by administering paracetamol and measuring the urinary excretion of its main metabolites. Paracetamol glucuronate was increased by levels of cysteine and mercapturic derivatives of paracetamol did not vary, whereas sulfate derivatives were decreased in epileptic patients. Plasma N-acetyl-transferase activity did not vary in either group. Hydroxylated cortisol and paracetamol glucuronide excretion were not correlated in the same individuals, and no correlation was found between the ratio of 6-beta-OH-cortisol/17-OH-corticosteroids and the plasma levels of diphenylhydantoin or phenobarbital. Oxidation of cortisol and conjugation of paracetamol were controlled with different mechanisms, varied considerably between individuals and were not predictive of the pharmacokinetics of the inducers in treated patients.

Paracetamol and phenacetin

Since their synthesis in the late 1800s paracetamol (acetaminophen) and phenacetin have followed divergent pathways with regard to their popularity as mild analgesic/antipyretic drugs. Initially, paracetamol was discarded in favour of phenacetin because the latter drug was supposedly less toxic. Today the opposite is true, and paracetamol, along with aspirin, has become one of the two most popular 'over-the-counter' non-narcotic analgesic agents. This marked increase in the wide approval attained by paracetamol has been accompanied by the virtual commercial demise of phenacetin because of its role, albeit somewhat circumstantial, in causing analgesic nephropathy. Both paracetamol and phenacetin are effective mild analgesics, suitable for treating mild to moderate pain, and their actions are broadly comparable with those of aspirin and related salicylates, although they do not appear to possess significant anti-inflammatory activity. Since a major portion of a dose of phenacetin is rapidly metabolised to paracetamol, it seems possible that phenacetin owes some of its therapeutic activity to its main metabolite, paracetamol, whereas its most troublesome side effect (methaemoglobinaemia) is due to another metabolite, p-phenetidine. The mechanism of action of paracetamol is poorly defined, although it has been speculated that it may selectively inhibit prostaglandin production in the central nervous system, which would account for its analgesic/antipyretic properties. The lack of any significant influence on peripheral cyclooxygenase would explain the absence of anti-inflammatory activity. At therapeutic doses paracetamol is well tolerated and produces fewer side effects than aspirin. The most frequently reported adverse effect associated with paracetamol is hepatotoxicity, which occurs after acute overdosage (usually doses greater than 10 to 15g are needed) and, very rarely, during long term treatment with doses at the higher levels of the therapeutic range. Paracetamol damages the liver through the formation of a highly reactive metabolite which is normally inactivated by conjugation with glutathione. Overdoses of paracetamol exhaust glutathione stores, thus allowing the accumulation of this toxic metabolite which covalently binds with vital cell elements and can result in liver necrosis. Glutathione precursors (notably intravenous N-acetylcysteine) have proved remarkably successful in treating paracetamol overdose, as long as treatment is initiated within 10 hours.(ABSTRACT TRUNCATED AT 400 WORDS)

Non-narcotic analgesics. Problems of overdosage

The first cases of fulminant hepatic failure due to paracetamol poisoning were reported in 1966, and in the United Kingdom this condition is now responsible for more cases of acute hepatic failure than any other cause. Adults account for the majority of serious and fatal cases of paracetamol poisoning and it is extremely rare for young children to ingest sufficient paracetamol to cause more than minimal liver damage. A single measurement of the plasma paracetamol concentration is an accurate predictor of liver damage provided that it is taken not earlier than 4 hours after ingestion of the overdose. Peak disturbance of liver function occurs 2 to 4 days after the overdose, often accompanied by mild jaundice, after which recovery is usually rapid and complete. In a few patients, fulminant hepatic failure, manifested by increasing jaundice and encephalopathy, may develop by the third to fifth day. Acute renal failure may complicate paracetamol poisoning, often in the context of severe liver damage. Renal failure, which is often non-oliguric, typically becomes apparent 24 to 72 hours after overdosage. The treatment of paracetamol intoxication should include gastric lavage, which has been shown to be of value for up to 6 hours after ingestion of a paracetamol overdose. Further general treatment may include parenteral fluid replacement and a prophylactic infusion of dextrose (5-10%) in patients at risk of hepatic failure. Specific protective agents in those patients at risk of paracetamol-induced liver damage include N-acetylcysteine and methionine which are most effective if given within 8 to 10 hours of ingestion of the overdose. Hepatic and renal failure should be managed conventionally. In recent years in the United Kingdom there has been a gradual decline in the number of hospital admissions and the number of deaths from aspirin poisoning. Salicylates in overdose directly stimulate the respiratory centre and so cause a respiratory alkalosis. Metabolic acidosis occurs in severe poisoning because of impairment of the oxidative metabolism of energy substrates. At very high salicylate concentrations respiratory depression may occur, possibly associated with neuroglycopenia, adding respiratory acidosis to the worsening metabolic acidosis. In addition to a mixed acid-base disturbance, hypokalaemia and hypoglycaemia may be present. Nausea and vomiting increase the fluid deficit. If dehydration is sufficiently severe, decreasing cardiac output may hasten development of lactic acidosis and acute renal failure.(ABSTRACT TRUNCATED AT 400 WORDS)