Liver failure induced by paracetamol

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

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

Effect of Ketorolac on the Prevention of Postoperative Catheter-Related Bladder Discomfort in Patients Undergoing Robot-Assisted Laparoscopic Radical Prostatectomy: A Randomized, Double-Blinded, Placebo-Controlled Study

Urinary catheterization can cause catheter-related bladder discomfort (CRBD). Ketorolac is widely used for pain control. Therefore, we evaluated the effect of ketorolac on the prevention of CRBD in patients undergoing robot-assisted laparoscopic radical prostatectomy (RALP). All patients were randomly allocated to the ketorolac group or the control group. The primary outcome was CRBD above a moderate grade at 0 h postoperatively. CRBD above a moderate grade at 1, 2, and 6 h was also assessed. Postoperative pain, opioid requirement, ketorolac-related complications, patient satisfaction, and hospitalization duration were also assessed. The incidence of CRBD above a moderate grade at 0 h postoperatively was significantly lower in the ketorolac group (21.5% vs. 50.8%, p = 0.001) as were those at 1, 2, and 6 h. Pain scores at 0 and 1 h and opioid requirement over 24 h were significantly lower in the ketorolac group, while patient satisfaction scores were significantly higher in the ketorolac group. Ketorolac-related complications and hospitalization duration were not significantly different between the two groups. This study shows ketorolac can reduce postoperative CRBD above a moderate grade and increase patient satisfaction in patients undergoing RALP, suggesting it is a useful option to prevent postoperative CRBD.

Novel circulating- and imaging-based biomarkers to enhance the mechanistic understanding of human drug-induced liver injury

Liver safety biomarkers in current clinical practice are recognized to have certain shortcomings including their representation of general cell death and thus lacking in indicating the specific underlying mechanisms of injury. An informative panel of circulating- and imaging-based biomarkers, will allow a more complete understanding of the processes involved in the complex and multi-cellular disease of drug-induced liver injury; potentially preceding and therefore enabling prediction of disease progression as well as directing appropriate, existing or novel, therapeutic strategies. Several putative liver safety biomarkers are under investigation as discussed throughout this review, informing on a multitude of hepatocellular mechanisms including: early cell death (miR-122), necrosis (HMGB1, K18), apoptosis, (K18), inflammation (HMGB1), mitochondrial damage (GLDH, mtDNA), liver dysfunction (MRI, MSOT) and regeneration (CSF1). These biomarkers also hold translational value to provide important read across between in vitro-in vivo and clinical test systems. However, gaps in our knowledge remain requiring further focussed research and the ultimate qualification of key exploratory biomarkers. Relevance for patients: this novel multi-modal approach of assessing drug-induced liver injury could potentially enable better patient stratification and enhance treatment strategies. Ultimately, this could reduce unnecessary treatment, also decreasing hospital bed occupancy, whilst ensuring early and accurate identification of patients needing intervention.

Prothrombin time prolongation in paracetamol poisoning: a relevant marker of hepatic failure?

The association between paracetamol overdose and prolonged prothrombin time due to hepatic failure is well recognized. However, little is known of the possibility that paracetamol overdose can prolong the prothrombin time without overt hepatic failure. The few data from the literature suggest this is either due to a reduction in the functional levels of the vitamin K-dependent clotting factors by elevated doses of paracetamol, or a consequence of the administration of the antidote N-acetylcystein. The three reported cases provide further evidence that paracetamol overdose can be associated with a prolongation in the prothrombin time without overt hepatic failure. Even though the prothrombin time provides useful prognosis information, decisions regarding the management of these patients should not solely be based on this endpoint to avoid misinterpretation of the accuracy and the severity of liver failure.

A multicentre programme of clinical and public health research in support of the National Suicide Prevention Strategy for England

Objectives

To carry out a programme of linked research studies aimed at improving the management of self-harm, reducing the incidence of suicide and providing reliable data to evaluate the impact of theNational Suicide Prevention Strategy for England(2002).

Methods

There were four research streams: (1) we studied inquest records from 12 coroners and Ministry of Justice data to assess the accuracy of official suicide statistics; (2) we used Office for National Statistics mortality statistics, data from the Multicentre Study of Self-harm in England, national liver unit data, prescription data and patient interviews to assess (a) the impact of paracetamol (acetaminophen) pack size restrictions (1998), (b) the impact of withdrawal of co-proxamol in 2007 and (c) the relative toxicity in overdose of commonly used antidepressants; (3) we carried out 3-month audits of self-harm management in 32 hospitals to investigate variations between hospitals and the impact of management on repeat self-harm; and (4) we developed and piloted letter-based contact interventions aimed at reducing self-harm.

Key findings

(1) Between 1990 and 2005, the proportion of researcher-defined suicides given a verdict of suicide by the 12 coroners studied decreased by almost 7%, largely because of the increased use of misadventure/accident verdicts for deaths thought, on clinical review, to be suicides. Use of narrative verdicts increased markedly. Coroners who gave more narrative verdicts also gave fewer suicide verdicts, and geographical variations in the use of narrative verdicts appeared to distort reliable assessment of small-area differences in suicide rates. 2(a) UK legislation to reduce pack sizes of paracetamol was followed by a 43% reduction in number of deaths and a 61% reduction in registrations for liver transplantation over the next 11 years. Paracetamol overdoses were often impulsive and some were influenced by media (including the internet); sales outlets appeared mostly to be adhering to sales guidance. Smaller pack sizes of paracetamol for sale in Ireland compared with England did not result in a smaller number of tablets being taken in overdose. There was no clear evidence of an effect of the legislation on prescribing of non-steroidal anti-inflammatory drugs, nor on resulting gastrointestinal bleeds. 2(b) Withdrawal of co-proxamol from use in the UK resulted in approximately 600 fewer deaths than predicted between 2005 and 2010 based on previous trends, with no evidence of substitution by poisoning with other analgesics. 2(c) Of the tricyclic antidepressants, dosulepin and doxepin had the greatest toxicity. Citalopram was more toxic than other selective serotonin reuptake inhibitors. (3) There was marked variation between hospitals in the management of self-harm; effects of this variation on patient outcomes were unclear, although psychosocial assessment may have been associated with reduced repetition. Levels of specialist assessment remained static between 2001–2 and 2010–11, but service quality appeared to improve. (4) Findings of two pilot randomised controlled trials suggested that, although it would be feasible to scale up these interventions to full trials, these interventions might have low generalisability and be of limited benefit to patients.

Conclusion

Within the context of the strengths and limitations of the individual studies, this research programme has made significant additions to the evidence base related to suicide and self-harm prevention in the UK.

Study registration

A pilot study of a contact and information based intervention to reduce repeat self-harm; ISRCTN65171515.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

Long term effect of reduced pack sizes of paracetamol on poisoning deaths and liver transplant activity in England and Wales: interrupted time series analyses

OBJECTIVE

To assess the long term effect of United Kingdom legislation introduced in September 1998 to restrict pack sizes of paracetamol on deaths from paracetamol poisoning and liver unit activity.

DESIGN

Interrupted time series analyses to assess mean quarterly changes from October 1998 to the end of 2009 relative to projected deaths without the legislation based on pre-legislation trends.

SETTING

Mortality (1993-2009) and liver unit activity (1995-2009) in England and Wales, using information from the Office for National Statistics and NHS Blood and Transplant, respectively.

PARTICIPANTS

Residents of England and Wales.

MAIN OUTCOME MEASURES

Suicide, deaths of undetermined intent, and accidental poisoning deaths involving single drug ingestion of paracetamol and paracetamol compounds in people aged 10 years and over, and liver unit registrations and transplantations for paracetamol induced hepatotoxicity.

RESULTS

Compared with the pre-legislation level, following the legislation there was an estimated average reduction of 17 (95% confidence interval -25 to -9) deaths per quarter in England and Wales involving paracetamol alone (with or without alcohol) that received suicide or undetermined verdicts. This decrease represented a 43% reduction or an estimated 765 fewer deaths over the 11¼ years after the legislation. A similar effect was found when accidental poisoning deaths were included, and when a conservative method of analysis was used. This decrease was largely unaltered after controlling for a non-significant reduction in deaths involving other methods of poisoning and also suicides by all methods. There was a 61% reduction in registrations for liver transplantation for paracetamol induced hepatotoxicity (-11 (-20 to -1) registrations per quarter). But no reduction was seen in actual transplantations (-3 (-12 to 6)), nor in registrations after a conservative method of analysis was used.

CONCLUSIONS

UK legislation to reduce pack sizes of paracetamol was followed by significant reductions in deaths due to paracetamol overdose, with some indication of fewer registrations for transplantation at liver units during the 11 years after the legislation. The continuing toll of deaths suggests, however, that further preventive measures should be sought.

Impact of different pack sizes of paracetamol in the United Kingdom and Ireland on intentional overdoses: a comparative study

Background

In order to reduce fatal self-poisoning legislation was introduced in the UK in 1998 to restrict pack sizes of paracetamol sold in pharmacies (maximum 32 tablets) and non-pharmacy outlets (maximum 16 tablets), and in Ireland in 2001, but with smaller maximum pack sizes (24 and 12 tablets). Our aim was to determine whether this resulted in smaller overdoses of paracetamol in Ireland compared with the UK.

Methods

We used data on general hospital presentations for non-fatal self-harm for 2002 - 2007 from the Multicentre Study of Self-harm in England (six hospitals), and from the National Registry of Deliberate Self-harm in Ireland. We compared sizes of overdoses of paracetamol in the two settings.

Results

There were clear peaks in numbers of non-fatal overdoses, associated with maximum pack sizes of paracetamol in pharmacy and non-pharmacy outlets in both England and Ireland. Significantly more pack equivalents (based on maximum non-pharmacy pack sizes) were used in overdoses in Ireland (mean 2.63, 95% CI 2.57-2.69) compared with England (2.07, 95% CI 2.03-2.10). The overall size of overdoses did not differ significantly between England (median 22, interquartile range (IQR) 15-32) and Ireland (median 24, IQR 12-36).

Conclusions

The difference in paracetamol pack size legislation between England and Ireland does not appear to have resulted in a major difference in sizes of overdoses. This is because more pack equivalents are taken in overdoses in Ireland, possibly reflecting differing enforcement of sales advice. Differences in access to clinical services may also be relevant.

Anaphylactoid reactions to intravenous N-acetylcysteine: a prospective case controlled study

INTRODUCTION

Since its introduction in 1977, intravenous N-acetylcysteine has become the treatment of choice for paracetamol overdose. The aim of our study was to investigate the existence of predictive factors in the likelihood of developing anaphylactoid reactions to N-acetylcysteine.

METHODS

Prospective case-controlled study of all patients who presented to our emergency department (ED) between January 1997 and June 1999, and who were treated with intravenous N-acetylcysteine on the short stay observation ward.

RESULTS

Sixty-four patients received N-acetylcysteine infusions; thirty-one (48.4%) developed an anaphylactoid reaction. Nineteen patients who reacted were commenced on N-acetylcysteine prior to receipt of paracetamol concentrations and fifteen (48.4%) were categorised as high-risk. Seventy-one percent of reactions occurred within the first 15 min. Thirteen patients who developed a reaction, had levels which fell below the treatment lines. The levels of a further nine reactors lay above the high-risk but below the normal-risk lines. Only five patients who reacted had levels above the normal-risk line. Two of the patients who reacted to intravenous N-acetylcysteine presented at a later date with a further paracetamol overdose. Both required treatment with intravenous N-acetylcysteine, the first bag being infused over one hour. Neither developed a reaction.

CONCLUSION

We report a substantially higher incidence of anaphylactoid reactions to intravenous N-acetylcysteine than has previously been documented. It appears that these reactions are more likely to occur in high-risk patients, when plasma paracetamol concentrations were found to be below the treatment lines and in late presenters. Perhaps, giving the loading dose of N-acetylcysteine over 60 min could reduce the incidence of adverse reactions.

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

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Effects of legislation restricting pack sizes of paracetamol and salicylate on self poisoning in the United Kingdom: before and after study

OBJECTIVE

To evaluate the effects on suicidal behaviour of legislation limiting the size of packs of paracetamol and salicylates sold over the counter.

DESIGN

Before and after study.

SETTING

UK population, with detailed monitoring of data from five liver units and seven general hospitals, between September 1996 and September 1999.

SUBJECTS

People who died by suicidal or accidental overdose with paracetamol or salicylates or who died of undetermined causes; patients admitted to liver units with hepatic paracetamol poisoning; patients presenting to general hospitals with self poisoning after taking paracetamol or salicylates.

MAIN OUTCOME MEASURES

Mortality from paracetamol or salicylate overdose; numbers of patients referred to liver units or listed for liver transplant; numbers of transplantations; numbers of overdoses and tablets taken; blood concentrations of the drugs; prothrombin times; sales to pharmacies and other outlets of paracetamol and salicylates.

RESULTS

Numbers of tablets per pack of paracetamol and salicylates decreased markedly in the year after the change in legislation on 16 September 1998. The annual number of deaths from paracetamol poisoning decreased by 21% (95% confidence interval 5% to 34%) and the number from salicylates decreased by 48% (11% to 70%). Liver transplant rates after paracetamol poisoning decreased by 66% (55% to 74%). The rate of non-fatal self poisoning with paracetamol in any form decreased by 11% (5% to 16%), mainly because of a 15% (8% to 21%) reduction in overdoses of paracetamol in non-compound form. The average number of tablets taken in paracetamol overdoses decreased by 7% (0% to 12%), and the proportion involving >32 tablets decreased by 17% (4% to 28%). The average number of tablets taken in salicylate overdoses did not decrease, but 34% fewer (2% to 56%) salicylate overdoses involved >32 tablets. After the legislation mean blood concentrations of salicylates after overdose decreased, as did prothrombin times; mean blood concentrations of paracetamol did not change.

CONCLUSION

Legislation restricting pack sizes of paracetamol and salicylates in the United Kingdom has had substantial beneficial effects on mortality and morbidity associated with self poisoning using these drugs.

Deliberate self-harm in adolescents in Oxford, 1985-1995

Deliberate self-harm (DSH) has been one of the major health problems of adolescents in the U.K. for many years. Any changes in rates of DSH or the demographic characteristics of the patient population are likely to have important implications for clinical services and for future suicidal behaviour. Following a decline in rates in the late 1970s and mid 1980s, there were signs in the late 1980s that rates were beginning to increase again. We have used data collected by the Oxford Monitoring System for Attempted Suicide on the basis of patients presenting to the general hospital in Oxford to review trends in DSH in under 20-year-olds between 1985 and 1995. There was a substantial increase in the numbers of teenage DSH patients during the 11-year study period, with an increase between 1985-1986 and 1994-1995 of 27.7% in males, 28.3% in females, and 28.1% overall. There were no demographic changes within the catchment area to explain a change of this size. As rates of repetition of DSH also increased in both sexes during the study period the overall number of episodes of DSH rose even more between 1985-1986 and 1994-1995 (+56.9% in males, +46.3% in females, and +49.4% overall). As in previous studies the majority of adolescents had interpersonal problems and/or difficulties with studying or employment. Self-poisoning with paracetamol and paracetamol compounds became increasingly common such that by 1995 these were used in almost two-thirds of overdoses. The recent increase in DSH in adolescents has important implications for general hospital and adolescent psychiatric services. The greater frequency of repetition of DSH may herald increased future suicide rates. The case for restricting the amount of paracetamol available is overwhelming. Evaluative trials of specific interventions following adolescent DSH are urgently required.

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.

Effect of endotracheal suctioning on the intracerebral haemodynamics of patients in fulminant hepatic failure

Fulminant hepatic failure is a severe impairment of liver function in someone who has had previously normal liver function. The patients presenting to intensive therapy units have generally had a rapid deterioration which requires prompt intervention and treatment. The first part of this paper gives a detailed review of the aetiology, physiology and management of the disease process. Medical and nursing care of these patients is critical; any adverse intervention may affect outcome. A literature review and small study of the intervention of endotracheal suctioning and its effects on intracranial pressure and cerebral perfusion pressure is described.

Use of paracetamol for suicide and non-fatal poisoning in the UK and France: are restrictions on availability justified?

OBJECTIVE

To investigate the relationship between the availability of paracetamol and its use for overdose and suicide.

DESIGN

Analysis of routinely collected information on time trends for paracetamol suicides, non-fatal overdoses, and sales.

SETTING

England and Wales and France.

RESULTS

There were strong correlations between trends in paracetamol sales in the UK and trends in non-fatal paracetamol overdose in Oxford between 1976 and 1993 (Spearman's r = 0.86; 95% confidence interval (CI) 0.54, 0.96) and between paracetamol sales and non-fatal overdoses in France between 1974 and 1990 (r = 0.99; 95% CI 0.97, 1.00). Sales figures were also correlated with paracetamol related suicides in both England and Wales, 1983-91 (r = 0.72; 95% CI 0.11, 0.94) and France, 1974-90 (r = 0.79; 95% CI 0.50, 0.92). Similarly strong relationships were observed between trends in non-fatal overdoses and suicide by paracetamol poisoning in England and Wales (r = 0.85; 95% CI 0.61, 0.95) and France (r = 0.79; 95% CI 0.50, 0.92). It is estimated that approximately 32,000 overdoses involving paracetamol occur annually in England and Wales. Fatality rates from paracetamol overdose were four times as high in England and Wales (0.4%, 95% CI 0.38, 0.46) as in France (0.1%, 95% CI 0.06, 0.17).

CONCLUSION

Trends towards greater availability of paracetamol are paralleled by increases in its use for both non-fatal overdose and suicide. Paracetamol related morbidity and mortality seem to be less frequent in France where the quantity of paracetamol in a single purchase is limited. Although not conclusive, these data add to a body of evidence which suggests that restrictions in the quantity of paracetamol available as a single purchase in the UK may reduce suicide and liver failure related to paracetamol.

Protective effects of diallyl sulfide on acetaminophen-induced toxicities

Diallyl sulfide (DAS), a major flavour component of garlic, is known to modulate drug metabolism and may protect animals from chemically induced toxicity and carcinogenesis. In this study the effects of DAS on the oxidative metabolism and hepatotoxicity induced by acetaminophen (APAP) in rats were investigated. In the hepatotoxicity evaluation of Fischer 344 rats there was a dose-dependent increase in the odds of mortality rate by APAP (P = 0.009); DAS treatment significantly protected rats from APAP-related mortality (P = 0.026). Liver toxicity determined by lactate dehydrogenase activity was significantly increased by APAP treatment (0.75 g/kg). Pretreatment with DAS protected animals from APAP-induced liver toxicity in a time- and dose-dependent fashion. Treatment of DAS (50 mg/kg) 3 hr after APAP dosing significantly (P < 0.05) protected rats from APAP-induced liver toxicity. The metabolism of APAP (50 microM) in vitro was significantly inhibited by DAS (0.3-1 mM) in liver microsomes isolated from F344 rats. As the effect of DAS on APAP-induced hepatotoxicity in vivo was observed only when DAS was administered before or shortly after (< 3 hr) APAP dosing, data suggested that the protective effect of DAS is mainly at the metabolic activation step of APAP. However, the possibility that DAS may also have effects on other drug metabolism systems, such as glutathione (GSH) and glutathione S-transferases, cannot be ruled out.

Hospitalisation for deliberate self-poisoning in Scotland from 1981 to 1993: trends in rates and types of drugs used

BACKGROUND

Rates of self-poisoning fell during the 1980s, although recent reports suggest this trend may have reversed.

METHODS

Data on all hospital discharges with a diagnosis of deliberate self-poisoning were obtained from the Information and Statistics Division of the NHS in Scotland. Rates of self-poisoning were investigated by overall trend, and for trends by age and by type of drug.

RESULTS

Deliberate self-poisoning rates for men and women began increasing in the late 1980s, and did so steadily during the early 1990s. Because the rates are increasing faster in men, the traditional excess of self-poisoning among women is being eroded. For men rates increased in all age groups up to the age of 60, but the greatest rise occurred between ages 15-29. For women the increase was largely restricted to 15-24-year-olds, and rates fell among women over the age of 50. Self-poisoning with paracetamol increased most rapidly; in contrast to aspirin which showed little change. Opiate analgesics, antirheumatics, antidepressants and antipsychotics have also shown some increase in their use in both genders. There has been a substantial fall in the use of benzodiazepines in women, but little change among men.

CONCLUSION

Rapid increases in self-poisoning particularly among young adults present a serious public health problem. Controlling this epidemic is made difficult because the principal drug involved, paracetamol, is readily available.

Paracetamol self-poisoning. Characteristics, prevention and harm reduction

BACKGROUND

Paracetamol is now the most common drug used for self-poisoning in the UK and is associated with potentially fatal liver damage. Patients admitted to hospital because of paracetamol overdoses were studied in order to determine their characteristics and factors which might have deterred them from taking paracetamol or reduced the dangers of the overdose.

METHOD

Eighty patients were studied in hospital using a structured interview schedule, measures of depression and suicidal intent, information collected through the Oxford Monitoring System for Attempted Suicide, and the results of liver function tests.

RESULTS

Acute liver dysfunction (25 patients) was associated with consumption of more than 25 tablets (odds ration 4.46, 95% CI 1.31 to 17.41, P = 0.014). The proportionate use of tablets from blister packs (60%) and loose preparations (46%; 5 patients using both types) reflected their general availability. More of those who took tablets from a loose preparation consumed 25 or more tablets (69%) than those who used a blister-pack preparation (40%; odds ratio = 3.0, 95% CI 1.12 to 9.95, P = 0.028). Only 20 patients thought that any type of warning label would have deterred them from taking a paracetamol overdose.

CONCLUSIONS

Establishing a maximum number of tablets (e.g. 25) that can be available in individual preparations is likely to reduce the dangers of paracetamol self-poisoning. The potential effects of other measures are uncertain.

Acute lung injury in fulminant hepatic failure following paracetamol poisoning

BACKGROUND

There is little information on the incidence of acute lung injury or changes in the pulmonary circulation in acute liver failure. The aim of this study was to record the incidence of acute lung injury in fulminant hepatic failure caused by paracetamol poisoning, to document the associated pulmonary circulatory changes, and to assess the impact of lung injury on patient outcome.

METHODS

The degree of lung injury was retrospectively assessed by a standard scoring system (modified from Murray) in all patients with fulminant hepatic failure caused by paracetamol poisoning, admitted to the intensive care unit over a one year period. The severity of liver failure and illness, other organ system failure, and patient outcome were also analysed.

RESULTS

Twenty four patients with paracetamol-induced liver failure were admitted and nine developed lung injury of whom eight (33%) had severe injury (Murray score > 2.5). In two patients hypoxaemia contributed to death. Patients with lung injury had higher median encephalopathy grades (4 v 2 in the non-injured group) and APACHE II scores (29 v 16). Circulatory failure, requiring vasoconstrictor support, occurred in all patients with lung injury but in only 40% of those without. Cerebral oedema, as detected by abnormal rises in intracranial pressure, also occurred in all patients with lung injury but in only 27% of the non-injured patients. The incidence of renal failure requiring renal replacement therapy was similar in both groups (67% and 47%). Pulmonary artery occlusion pressures were normal in the lung injury group. Cardiac output was high (median 11.2 1/min), systemic vascular resistance low (median 503 dynes/s/cm-5), and pulmonary vascular resistance low (median 70 dynes/s/cm-5), but not significantly different from the group without lung injury. Mortality was much higher in the lung injury group than in the non-injured group (89% v 13%).

CONCLUSIONS

Acute lung injury was common in patients with paracetamol-induced fulminant hepatic failure and was associated with systemic circulatory failure and cerebral oedema. The development of acute lung injury was associated with high mortality.

Fracture of the accessory navicular

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The role of cytochrome P450 enzymes in hepatic and extrahepatic human drug toxicity

The human cytochrome P450 enzyme system metabolises a wide array of xenobiotics to pharmacologically inactive metabolites, and occasionally, to toxicologically active metabolites. Impairment of cytochrome P450 activity, which may be either genetic or environmental, may lead to toxicity caused by the parent compound itself. In practise, this usually only applies to drugs that have a narrow therapeutic index and when their clearance is critically dependent upon the fraction normally metabolised by that pathway. P450 enzymes may also convert the drug to a chemically reactive metabolite, which, if not detoxified, may lead to various forms of hepatic and extrahepatic toxicity, including cellular necrosis, hypersensitivity, teratogenicity, and carcinogenicity, depending on the site of formation and the relative stability of the metabolite, and the cellular macromolecule with which it reacts. Variation in the regulation and expression of the drug metabolising enzymes may play a key role in both interindividual variation in sensitivity to drug toxicity and tissue-specific damage. Avoidance of toxicity may be possible in rare instances by prediction of individual susceptibility or by designing new chemical entities that are metabolised by a range of enzymes (both cytochromes P450 and others) and do not undergo bioactivation.

The role of active metabolites in drug toxicity

Adverse drug reactions can be caused by the parent drug or a metabolite of that drug. The metabolite may be stable or chemically reactive, the resultant toxicity being either a direct extension of the pharmacology of the drug, or unrelated to the known pharmacology of the drug and dependent on the chemical properties of the compound. Many different organ systems may be affected, and there are several mechanisms involved in determining organ-specific, and sometimes cell-selective, toxicity. An imbalance between bioactivation of a drug to a toxic metabolite and its detoxification is of prime importance in determining individual susceptibility. Such an imbalance may be genetically determined or acquired and, furthermore, may be systemic or tissue-specific. Prevention of metabolite-mediated toxicity is possible once the mechanism of toxicity has been elucidated.

Prevention of suicide: aspirations and evidence

The Health of the Nation white paper set a target for 15% reduction in overall suicide rates by the year 2000. If the targets are to be achieved interventions must be identified which are of proved effectiveness. This paper examines the evidence on the available interventions and points of access to the population at risk. No single intervention has been shown in a well conducted randomised controlled trial to reduce suicide. The greatest potential seems to arise from limiting the availability of methods. In particular it is likely that the introduction of the catalytic convertor will lead to reduced lethality of care exhausts and reductions in suicide using this method. General practitioner education programmes, the effectiveness of lithium and maintenance antidepressants, and limits on the quantity of medicines available over the counter or on prescription should all be evaluated. Particular high risk groups include people recently discharged from psychiatric hospitals and those with a history of parasuicide. Many social processes affect suicide rates and these rather than specific interventions may help or hinder the ability to realise the Health of the Nation targets. Well conducted trials are essential to distinguish complex social processes from the effects of specific interventions for suicide prevention. This review of the available evidence offers little support for the aspiration that the posited targets can be achieved on the basis of current knowledge and current policy.