Renal impairment associated with an acute paracetamol overdose in the absence of hepatotoxicity

Lack of mitochondrial Cyp2E1 drives acetaminophen-induced ER stress-mediated apoptosis in mouse and human kidneys: Inhibition by 4-methylpyrazole but not N-acetylcysteine

Acetaminophen (APAP) overdose causes liver injury and acute liver failure, as well as acute kidney injury, which is not prevented by the clinical antidote N-acetyl-L-cysteine (NAC). The absence of therapeutics targeting APAP-induced nephrotoxicity is due to gaps in understanding the mechanisms of renal injury. APAP metabolism through Cyp2E1 drives cell death in both the liver and kidney. We demonstrate that Cyp2E1 is localized to the proximal tubular cells in mouse and human kidneys. Virtually all the Cyp2E1 in kidney cells is in the endoplasmic reticulum (ER), not in mitochondria. By contrast, hepatic Cyp2E1 is in both the ER and mitochondria of hepatocytes. Consistent with this subcellular localization, a dose of 600 mg/kg APAP in fasted C57BL/6J mice induced the formation of APAP protein adducts predominantly in mitochondria of hepatocytes, but the ER of the proximal tubular cells of the kidney. We found that reactive metabolite formation triggered ER stress-mediated activation of caspase-12 and apoptotic cell death in the kidney. While co-treatment with 4-methylpyrazole (4MP; fomepizole) or the caspase inhibitor Ac-DEVD-CHO prevented APAP-induced cleavage of procaspase-12 and apoptosis in the kidney, treatment with NAC had no effect. These mechanisms are clinically relevant because 4MP but not NAC also significantly attenuated APAP-induced apoptotic cell death in primary human kidney cells. We conclude that reactive metabolite formation by Cyp2E1 in the ER results in sustained ER stress that causes activation of procaspase-12, triggering apoptosis of proximal tubular cells, and that 4MP but not NAC may be an effective antidote against APAP-induced kidney injury.

Acute Renal Impairment in Patients Due to Paracetamol Overdose in the Absence of Hepatic Impairment

In general, paracetamol poisoning is associated with hepatotoxicity and very rarely with renal impairment in the absence of significant hepatic impairment. Paracetamol poisoning associated with renal impairment is rare, and it is mostly associated with hepatotoxicity. Most patients with acute renal impairment show a pattern of acute tubular necrosis or injury based on their blood, clinical presentation, and imaging. The level of injury was found to be associated with the dose of paracetamol taken.

We describe a case of a 22-year-old patient presenting to the hospital with abdominal pain, back pain, and two episodes of vomiting after 36 hours of an intentional paracetamol overdose of 60 tablets. His lab results showed raised creatinine levels and C-reactive protein (CRP) despite normal liver function tests. His paracetamol and salicylate levels were not checked on his initial presentation. He was given N-acetyl cysteine (NAC) treatment for paracetamol overdose and had computed tomography of kidneys, ureters, and bladder (CT KUB) the following day, which showed mild, uncomplicated sigmoid diverticula. He was discharged the next day, but was readmitted two days later with severe abdominal pain and worsening renal function. He had an magnetic resonance imaging (MRI) abdomen that showed coronal/axial wedge like areas of relative hypo-intense change in the T2 acquisition. He received intravenous fluids and antibiotics, and his renal function improved. He was discharged home with outpatient follow-up and appeared to be fully recovered.

Prognostic factors of acetaminophen exposure in the United States: An analysis of 39,000 patients

Acetaminophen is a frequently used over-the-counter or prescribed medication in the United States. Exposure to acetaminophen can lead to acute liver cytolysis, acute liver failure, acute kidney injury, encephalopathy, and coagulopathy. This retrospective cohort study (1/1/2012 to 12/31/2017) investigated the clinical outcomes of intentional and unintentional acetaminophen exposure using the National Poison Data System data. The frequency of outcomes, chronicity, gender, route of exposure, the reasons for exposure, and treatments as described. Binary logistic regression was used to estimate the prognostic factors and odds ratios (OR) with 95% confidence intervals (CI) for outcomes. This study included 39,022 patients with acetaminophen exposure. Our study demonstrated that the likelihood of developing severe outcomes increased by aging (OR = 1.12, 95% CI: 1.08-1.015) and was lower in females (OR = 0.88, 95% CI: 0.78-0.99). Drowsiness/lethargy (OR = 1.48, 95% CI: 1.22-1.82), agitation (OR = 1.66, 95% CI: 1.11-2.50), coma (OR = 23.95, 95% CI: 17.05-33.64), bradycardia (OR = 2.29, 95% CI: 1.22-4.32), rhabdomyolysis (OR = 8.84, 95% CI: 3.71-21.03), hypothermia (OR = 4.1, 95% CI: 1.77-9.51), and hyperthermia 2.10 (OR = 2.10, 95% CI: 1.04-4.22) were likely associated with major outcomes or death. Treatments included intravenous N-acetylcysteine (61%), oral N-acetylcysteine (10%), vasopressor (1%), hemodialysis (0.7%), fomepizole (0.1%), hemoperfusion (0.03%), and liver transplant (0.1%). In conclusion, it is important to consider clinical presentations of patients with acetaminophen toxicity that result in major outcomes and mortality to treat them effectively.

The dark side of ibuprofen in the treatment of patent ductus arteriosus: could paracetamol be the solution?

INTRODUCTION

Patent ductus arteriosus (PDA) persistence is associated, in prematures, to several complications. The optimal PDA management is still under debate, especially regarding the best therapeutic approach and the time to treat. The available drugs are not exempt from contraindications and side effects; ibuprofen itself, although representing the first-choice therapy, can show nephrotoxicity and other complications. Paracetamol seems a valid alternative to classic nonsteroidal anti-inflammatory Drugs, with a lower toxicity. Areas covered: Through an analysis of the published literature on ibuprofen and paracetamol effects in preterm neonates, this review compares the available treatments for PDA, analyzing the mechanisms underlining ibuprofen-associated nephrotoxicity and the eventual paracetamol-induced hepatic damage, also providing an update of what has been yet demonstrated and a clear description of the still open issues. Expert Opinion: Paracetamol is an acceptable alternative in case of contraindication to ibuprofen; its toxicity, in this setting, is very low. Lower doses may be effective, with even fewer risks. In the future, paracetamol could represent an efficacious first-line therapy, although its safety, optimal dosage, and global impact have to be fully clarified through long-term trials, also in the perspective of an individualized and person-based therapy taking into account the extraordinary individual variability.

Characterization of Acetaminophen Toxicity in Human Kidney HK-2 Cells

Acetaminophen (APAP) overdose causes liver injury, but in some cases it is associated also with renal impairment. While several studies exist in relation to acetaminophen nephrotoxicity, no reports have been published describing intracellular changes related to APAP nephrotoxicity in vitro. Because proximal tubular cells are considered to constitute a secondary site of drug-induced injury after hepatocytes, our study's aim was to estimate the toxicity in the human HK-2 cell line. We used a range of APAP concentrations (1-10 mM) to examine toxicity in the cells (1-48 h). We evaluated cell viability using the WST-1 and LDH tests. Cells impairment was also determined by monitoring ROS production, glutathione levels. We proved that HK-2 cells are able to metabolize acetaminophen. We observed moderate impairment of cells already after 1 h of treatment based on a finding of increased ROS production and decreased cell viability. After 24 h, the results showed significant cellular impairment at all tested concentrations except for 1 mM APAP, but no glutathione depletion was found. We conclude that HK-2 cells are susceptible to acetaminophen toxicity but, unlike hepatocytes, it might be not linked to glutathione depletion.

Incidence and characterization of acute kidney injury after acetaminophen overdose

PURPOSE

Acute kidney injury (AKI) occurs in 2-10% of patients with acetaminophen (APAP) overdose. Elevation in creatinine (SCr) typically occurs 2 to 5 days after ingestion, with a mean peak on day 7, and normalization over a month. However, it remains unclear whether renal impairment occurs without hepatotoxicity. We hypothesized that APAP-associated acute renal failure occurs in patients with and without severe liver dysfunction after APAP overdose.

MATERIALS AND METHODS

We retrospectively evaluated all patients admitted to the Medical Intensive Care Unit at a tertiary hospital and received acetylcysteine between June 2009 and December 2014. Of the 303 patients meeting these criteria, 139 of these patients received acetylcysteine for APAP overdose. Of these patients, 138 had Model for End-Stage Liver Disease (MELD) Scores on Day 1 of admission. Using a modified MELD (m-MELD) score, only containing total bilirubin and international normalized ratio not the SCr, the median m-MELD score was calculated. Patients with m-MELD scores below the median were compared to those with scores above the median (low m-MELD score <2.9 or high m-MELD score >2.9).

RESULTS

Baseline demographics were similar in the two groups with the exception of more hypertension in the low m-MELD group (24 vs 7%; P= .02). Time to admission was shorter in the low m-MELD group (7.9 ± 9.3 vs. 25.7 ± 29.2 hours; P= .001). The mean admission APAP level was 96.9 (±119) μg/mL in the low compared to 52.3 (±85.3) μg/mL in the high m-MELD group (P= .012). Day one SCr (1.2 ± 0.9 vs 2.7 ± 2.2 mg/dL; P< .0001) and change from baseline to highest SCr (0.2 ± 0.3 vs. 2.7 ± 3.3 mg/dL; P< .0001) were both lower in the low m-MELD group compared to the high m-MELD group. In addition, renal failure resolved upon discharge in all 2 patients (3%) with AKI in the low m-MELD group as compared to only 19 patients (44%) in the high m-MELD group.

CONCLUSIONS

Mean day one SCr, maximum change in SCr, and lack of renal failure resolution were higher in patients with higher m-MELD scores. However, patients with low m-MELD scores presented much earlier than patients with high m-MELD scores and 26% developed AKI.

Early predictors of severe acetaminophen-induced hepatotoxicity in a paediatric population referred to a tertiary paediatric department

AIM

The data on severe acetaminophen-induced hepatotoxicity in children are very limited. This study explored the dose-response relationship between ingested acetaminophen and hepatotoxicity, the early biochemical and clinical predictors of hepatotoxicity, the impact of early N-acetylcysteine treatment on hepatotoxicity and the incidence of nephrotoxicity.

METHODS

We carried out a retrospective case study on 25 children aged 11-16 years with severe acetaminophen poisoning.

RESULTS

Initial biochemical parameters predicted hepatotoxicity, defined as the maximum levels of the international normalised ratio (INR) and alanine aminotransferase (ALT). Significant relationships were found between: (1) the maximal INR and, for example, the initial bilirubin (p = 0.0003) and initial phosphate (p = 0.003), (2) the maximal ALT and, for example, the initial INR (p = 0.0003) and initial creatinine (p = 0.002), (3) the number of prehospital vomiting episodes and, for example, the maximal INR (p = 0.013) and maximum ALT (p = 0.0005) and (4) the time of N-acetylcysteine initiation and, for example, maximum ALT (p = 0.001) and maximum gamma-glutamyl transferase (GGT) (p = 0.007). The incidence of nephrotoxicity was 12%. There was no significant relationship between the amount of ingested acetaminophen and the degree of hepatotoxicity.

CONCLUSION

Paediatric patients at increased risk of severe hepatotoxicity were identified by early biochemical parameters, prehospital vomiting episodes and latency time before N-acetylcysteine initiation.

Sub-acute toxicity studies of acetaminophen in Sprague Dawley rats

The aim of the present study was to evaluate the sub-acute oral toxicity of acetaminophen in Sprague Dawley (SD) rats at 250 to 1000 mg/kg body weight (b.wt.). The following observations were noticed during the study. No mortality in male and female rats, at and up to the dose of 1000 mg/kg b.wt. There were abnormal clinical signs observed on female animals at 1000 mg/kg b.wt. dose level. There were no difference in body weight gain and no effect on the daily feed consumption. No toxicologically significant effect on the haematological parameters but liver and kidney related biochemical parameter showed significant difference at 1000 mg/kg b.wt. in females. No toxicologically significant effect on the urinalysis parameters, absolute and relative organ weights and gross pathological alterations; whereas histopathological alterations were observed in female liver at dose level of 1000 mg/kg b.wt. were observed. Based on the findings of this study, the No Observed Adverse Effect Level (NOAEL) of acetaminophen in SD rats, following oral administration at the doses of 250, 500 and 1000 mg/kg on daily basis was found to be 500 mg/kg b.wt.

Paracetamol: a focus for the general pediatrician

Paracetamol (acetaminophen) is one of the most popular and widely used drugs for the treatment of pain and fever in children. This drug has multiple mechanisms of action, but its pharmacodynamic is still not well known. The central nervous system is the main site of action and it mirrors the paracetamol effect compartment. The recommended dosages and routes of administration should be different whether paracetamol is used for the treatment of pain or fever. For example, the rectal route, while being efficacious for the treatment of fever, should be avoided in pain management. Paracetamol is a safe drug, but some clinical conditions and concomitant drugs, which are frequent in clinical practice, may increase the risk of paracetamol toxicity. Therefore, it is important to optimize its administration to avoid overdoses and maximize its effect. The principal mediator of the paracetamol toxicity is the N-acetyl-p-benzo-quinone imine (NAPQI), a toxic product of the paracetamol metabolism, which could bind cysteine groups on proteins forming paracetamol-protein adduct in the liver.

CONCLUSION

Although frequently prescribed, the concept of "effect compartment concentration" and the possible co-factors that could cause toxicity at recommended doses are not familiar to all pediatricians and general practitioners. We reviewed the literature concerning paracetamol mechanisms of action, we highlighted some relevant pharmacodynamic concepts for clinical practice, and we summarized the possible risk factors for toxicity at therapeutic dosages.

[Acetaminophen (paracetamol) causing renal failure: report on 3 pediatric cases]

Renal failure secondary to acetaminophen poisoning is rare and occurs in approximately 1-2 % of patients with acetaminophen overdose. The pathophysiology is still being debated, and renal acetaminophen toxicity consists of acute tubular necrosis, without complication if treated promptly. Renal involvement can sometimes occur without prior liver disease, and early renal manifestations usually occur between the 2nd and 7th day after the acute acetaminophen poisoning. While therapy is exclusively symptomatic, sometimes serious metabolic complications can be observed. The monitoring of renal function should therefore be considered as an integral part of the management of children with acute, severe acetaminophen intoxication. We report 3 cases of adolescents who presented with acute renal failure as a result of voluntary drug intoxication with acetaminophen. One of these 3 girls developed severe renal injury without elevated hepatic transaminases. None of the 3 girls' renal function required hemodialysis, but one of the 3 patients had metabolic complications after her acetaminophen poisoning.

Acute kidney injury in patients admitted to a liver intensive therapy unit with paracetamol-induced hepatotoxicity

BACKGROUND

Paracetamol overdose can cause acute kidney injury (AKI) independent of its hepatotoxic effects. We aimed to determine the prevalence of AKI (AKI Network definition) in those with paracetamol-induced hepatotoxicity, identify factors associated with development, assess impact on the outcomes of patient survival and length of stay and determine the proportion of patients recovering renal function (estimated glomerular filtration rate > 60 mL/min) by the time of hospital discharge or transfer out.

METHODS

Between 2000 and 2007, patients admitted to a tertiary referral liver intensive therapy unit (LITU) with paracetamol-induced hepatotoxicity were identified from a prospectively maintained database and evaluated.

RESULTS

Those receiving a liver transplant were excluded (n = 54), leaving 302 patients. Renal function remained normal in 21%, the remainder developing AKI (Stages 1-8%, 2-6% and 3-65%). Vasopressor requirement, mechanical ventilation, higher admission phosphate and lower sodium levels along with a higher Day 3 lactate and lower haematocrit were associated with AKI. In survivors with AKI, 51% had recovery of renal function, while 7% remained dialysis dependant although none required it chronically. Overall, there was 25% mortality, all having Stage 3 AKI but AKI was only a univariate not multivariate predictor of reduced patient survival. AKI independently predicted longer length of stay.

CONCLUSIONS

AKI is very common in critically ill patients with paracetamol-induced hepatotoxicity requiring LITU admission. Although outcomes are poorer with AKI than with normal renal function, they are better than those found in other intensive therapy unit populations. Gradual recovery of renal function is seen in all patients.

[Acute renal failure after acetaminophen poisoning: report of three cases]

PURPOSE

Management of acetaminophen overdose focuses on the risk hepatic failure. However, acute renal failure, although less frequent, can lead to serious metabolic complications and require hemodialysis. We report three cases of acute renal failure related to acetaminophen overdose.

CLINICAL FEATURES

Three patients, aged 17-46 yr ingested acetaminophen 19 to 32 g, and were admitted to the intensive care unit because of acute liver failure without hepatic coma. While liver function improved, each patient developed acute renal failure starting on the fourth day. Four sessions of hemodialysis were required in one patient because of anuria. Hepatic function improved from the fourth to the ninth day in each case, whereas renal function recovered later, 10-20 days after ingestion. Investigations were negative for other causes of renal failure, and acute tubular necrosis due to acetaminophen was suspected.

CONCLUSION

The pathophysiology of this type of acute tubular necrosis remains unclear and thus, there is no specific treatment. Nevertheless, in all cases of acetaminophen overdose, we suggest following serum creatinine levels during the first week, regardless of the degree hepatic failure or quantity of acetaminophen ingested.

Experiences of a Poison Center Network with Renal Insufficiency in Acetaminophen Overdose: An Analysis of 17 Cases

OBJECTIVE

Renal insufficiency is less common than liver failure in acetaminophen overdose but renal tubular damage occurs even in the absence of hepatotoxicity. Data published on this topic are rare consisting mostly of case reports or reports in a small number of patients. Presently, a larger number of patients with renal insufficiency associated with acetaminophen overdose should be analyzed using a multicenter approach.

STUDY DESIGN

Retrospective analysis of patients with acetaminophen-related nephrotoxicity reported to a poison center network from 1995 to 2003. Renal insufficiency was defined as elevated serum creatinine of more than double of the normal range (>2.4 mg/dL [212 micromol/L]). Patients were classified into 4 groups (A: creatinine 2.4-5.0 mg/dL, B: creatinine>5.0 mg/dL requiring no dialysis, C: creatinine>5.0 mg/dL requiring dialysis, D: creatinine>5.0 mg/dL with fatal outcome).

RESULTS

Seventeen patients were included (8 female, 9 male, average age 31.7 +/- 21.1 yrs) with 6 patients in group A (B: 7, C: 2, D: 2). In 5 patients renal insufficiency occurred without elevation of liver enzymes. Regarding possible risk factors 5 patients concomitantly ingested nephrotoxic substances, 4 presented with dehydration due to vomiting, 4 with chronic excessive dosing (overdose) of acetaminophen, 3 showed pre-existing renal insufficiency, 2 pre-existing liver disease and 2 died with multiple organ failure.

CONCLUSIONS

Renal insufficiency in acetaminophen overdose mostly resolved without dialysis and occurred isolated without hepatotoxicity in less than one-third of the investigated patients. Conditions which might play a role as influencing factors for renal complications included concomitant ingestion of nephrotoxic drugs, dehydration, chronic excessive dosing (overdose) of acetaminophen, pre-existing renal or liver disease and multiple organ failure. Renal function should be monitored in acetaminophen overdose particularly in patients showing the latter comorbidity.

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.

Paracetamol induced hepatotoxicity

AIM

To identify the clinical and biochemical risk factors associated with outcome of paracetamol induced significant hepatotoxicity in children.

METHODS

Retrospective case notes review of those with paracetamol overdose admitted from 1992 to 2002. Patients were analysed in two groups: group I recovered after conservative treatment and group II developed progressive liver dysfunction and were listed for liver transplantation.

RESULTS

Of 51 patients (6 males, 45 females, aged 0.8-16.1 years), 6 (aged <7 years) received cumulative multiple doses, and 45 a single large overdose (median 345 mg/kg, range 91-645). The median (range) interval to hospital at presentation post-ingestion was 24 hours (4-65) and 44 hours (24-96) respectively in groups I and II. Patients received standard supportive treatment including N-acetylcysteine. All children in group I survived. In group II, 6/11 underwent orthotopic liver transplantation (OLT) and 2/6 survived; 5/11 died awaiting OLT. Cerebral oedema was the main cause of death. Children who presented late to hospital for treatment and those with progressive hepatotoxicity with prothrombin time >100 seconds, hypoglycaemia, serum creatinine >200 micromol/l, acidosis (pH <7.3), and who developed encephalopathy grade III, had a poor prognosis or died. Although hepatic transaminase levels were markedly raised in both groups, there was no correlation with necessity for liver transplantation or death.

CONCLUSION

Accidental or incidental paracetamol overdose in children may be associated with toxic liver damage leading to fulminant liver failure. Delayed presentation and/or delay in treatment, and hepatic encephalopathy > or =grade III were significant risk factors, implying poor prognosis and need for OLT. Prompt identification of high risk patients, referral to a specialised unit for management, and consideration for liver transplantation is essential.

Nephrotoxicity after acute severe acetaminophen poisoning in adolescents

OBJECTIVE

To determine the rate of acetaminophen related nephrotoxicity in adolescents who present after acute severe acetaminophen intoxication and to identify potential predictors of this outcome.

STUDY DESIGN

Retrospective analysis of consecutive patients between the ages of 12 and 18 years who were admitted at a tertiary care children's hospital for treatment of acute severe acetaminophen intoxication with N-acetylcysteine. The main outcome measure was the frequency of acetaminophen-related nephrotoxicity, defined as abnormal blood urea nitrogen (>6.4 mmol/L or > 18 mg/dL) and/or elevated creatinine (97.2 micromol/L or > 1.1 mg/dL) in association with one or both of the following: elevated blood pressure (systolic blood pressure > 140 mm Hg/diastolic blood pressure >85) or abnormal urinalysis (urinalysis with hematuria or proteinuria). Statistical analyses used were measures of central tendency, Student's t-test, Mann-Whitney, and multivariate logistic regression.

RESULTS

Fourty-five patients were included. Acetaminophen-related nephrotoxicity occurred in 4 (8.9%) cases. One victim developed severe renal injury in association with elevated hepatic transaminases. Intergroup analyses revealed no statistically significant association between acetaminophen-related nephrotoxicity and amount/kg of acute severe acetaminophen ingested, delay in treatment with N-acetylcysteine, or measures of hepaticfunction.

CONCLUSIONS

Acetaminophen-related nephrotoxicity occurred in 8.9% [95% CI: 4.52, 20.48] of children with severe overdose. There are no obvious predictors of this complication of acetaminophen overdose. Because the occurrence of renal injury can not be predicted, serial blood pressure, blood urea nitrogen/creatinine, and urinalysis should be considered an integral part of the management of children with acute, severe acetaminophen intoxication.

Acetaminophen: acute and chronic effects on renal function

Acetaminophen (APAP) is normally metabolized in the liver and kidney by P450 enzymes. No toxicity is observed with therapeutic doses of APAP. However, after ingestion of large quantities of APAP (>2,000 mg/kg), highly reactive quinones, metabolites of APAP, are generated; these react with glutathione and sulfhydryl groups on critical proteins, resulting in cellular dysfunction and hepatic and renal toxicity. The P450 metabolizing enzymes differ somewhat in character between the liver and kidney. Factors that enhance renal toxicity include chronic liver disease, possibly gender, concurrent renal insults, and conditions that alter the activity of P450-metabolizing enzyme systems. Acute renal toxicity is characterized by cellular injury primarily confined to the proximal tubule and significant reductions in glomerular filtration rate. However, there is little evidence that chronic administration of APAP contributes to chronic renal disease and analgesic nephropathy. The only report on this subject suggests that combination therapy with aspirin is required for medullary damage in rats. No evidence exists for the development of chronic analgesic nephropathy with APAP alone. Epidemiologic studies in healthy individuals have failed to demonstrate a significant correlation between APAP use and chronic renal disease and classic analgesic nephropathy. Therefore, large doses of APAP can produce both renal and hepatic failure, but little evidence exists for production of classic analgesic nephropathy with the use of APAP alone.

Paracetamol overdose: pathophysiology and nursing management

Paracetamol overdose now represents one third of all self-poisoning cases. In contrast to other drugs, the use of paracetamol as a self-poisoning agent is increasing. As very large doses of the drug cause severe liver injury, which can result in fulminant hepatic failure when left untreated, it is essential that nurses have a complete understanding of the mechanisms of normal paracetamol metabolism, effects of overdosage and treatment strategies to guide the nursing management of clients. This review therefore critically examines the pathophysiology and nursing management of clients with acute paracetamol overdosage.

Retinol binding proteinuria and phosphaturia: markers of paracetamol-induced nephrotoxicity

The occurrence of hypophosphataemia in paracetamol overdose suggests that nephrotoxicity is common, impaired renal tubular reabsorption of phosphate indicating renal damage. To investigate the potential nephrotoxicity of paracetamol, we studied 148 consecutive patients with paracetamol overdose. Serial clinical and biochemical measurements were made, and a fasting overnight urine collection was obtained for creatinine (Cr), phosphate and retinol-binding protein (RBP) determination. Renal threshold phosphate concentration (TmPO4/GFR) was determined from urinary parameters by an established nomogram. The degree of hypophosphataemia correlated with the severity of overdose, and with TmPO4/GFR. The median RBP/Cr ratio was higher in those patients exhibiting biochemical hepatotoxicity compared with those without hepatotoxicity, in whom median RBP/Cr was not significantly higher than controls. Within the group of patients showing biochemical hepatotoxicity, there was a correlation between log RBP/Cr and TmPO4/GFR. RBP/Cr ratio is a less sensitive marker of renal tubular toxicity than phosphaturia in these patients, and may indicate a different mechanism of toxicity.

Paracetamol poisoning and the kidney

Nephrotoxicity is less common than hepatotoxicity in paracetamol overdose but renal tubular damage and acute renal failure occur even in the absence of hepatotoxicity. It is possible that antidotal therapy with agents such as N-acetylcysteine may not prevent renal toxicity and, indeed, on the basis of animal work, may actually potentiate tubular damage. Careful clinical attention should be paid to renal function in patients poisoned with paracetamol.