Childhood hepatotoxicity with paracetamol doses less than 150 mg/kg per day

Acetaminophen treatment in children and adults with spinal muscular atrophy: a lower tolerance and higher risk of hepatotoxicity

Acute liver failure has been reported sporadically in patients with spinal muscular atrophy (SMA) and other neuromuscular disorders with low skeletal muscle mass receiving recommended dosages of acetaminophen. It is suggested that low skeletal muscle mass may add to the risk of toxicity. We aimed to describe the pharmacokinetics and safety of acetaminophen in patients with SMA. We analyzed acetaminophen metabolites and liver biomarkers in plasma from SMA patients and healthy controls (HC) every hour for six or eight hours on day 1 and day 3 of treatment with therapeutic doses of acetaminophen. Twelve patients with SMA (six adults and six children) and 11 HC participated in the study. Adult patients with SMA had significantly lower clearance of acetaminophen compared to HC (14.1 L/h vs. 21.5 L/h). Formation clearance of acetaminophen metabolites, glucuronide, sulfate, and oxidative metabolites were two-fold lower in the patients compared to HC. The liver transaminases and microRNAs increased nine-fold in one adult SMA patient after two days of treatment. The other patients and HC did not develop abnormal liver biomarkers. In this study, patients with SMA had lower clearance and slower metabolism of acetaminophen, and one patient developed liver involvement. We recommend giving 15 mg/kg/dose to SMA adults (with a maximum of 4000 mg/day) and monitoring standard liver biomarkers 48 h after first-time treatment of acetaminophen.

Fluorescent probe for the imaging of superoxide and peroxynitrite during drug-induced liver injury

Drug-induced liver injury (DILI) is an important cause of potentially fatal liver disease. Herein, we report the development of a molecular probe (LW-OTf) for the detection and imaging of two biomarkers involved in DILI. Initially, primary reactive oxygen species (ROS) superoxide (O₂˙^-) selectively activates a near-infrared fluorescence (NIRF) output by generating fluorophore LW-OH. The C[double bond, length as m-dash]C linker of this hemicyanine fluorophore is subsequently oxidized by reactive nitrogen species (RNS) peroxynitrite (ONOO^-), resulting in cleavage to release xanthene derivative LW-XTD, detected using two-photon excitation fluorescence (TPEF). An alternative fluorescence pathway can occur through cleavage of LW-OTf by ONOO^- to non-fluorescent LW-XTD-OTf, which can react further with the second analyte O₂˙^- to produce the same LW-XTD fluorescent species. By combining NIRF and TPEF, LW-OTf is capable of differential and simultaneous detection of ROS and RNS in DILI using two optically orthogonal channels. Probe LW-OTf could be used to detect O₂˙^- or O₂˙^- and ONOO^- in lysosomes stimulated by 2-methoxyestradiol (2-ME) or 2-ME and SIN-1 respectively. In addition, we were able to monitor the chemoprotective effects of tert-butylhydroxyanisole (BHA) against acetaminophen (APAP) toxicity in living HL-7702 cells. More importantly, TPEF and NIRF imaging confirmed an increase in levels of both O₂˙^- and ONOO^- in mouse livers during APAP-induced DILI (confirmed by hematoxylin and eosin (H&E) staining).

Normal Dose Paracetamol in Muscular Dystrophy Patients – is it Normal?

A 16-year-old male with Becker muscular dystrophy was admitted to hospital with a significant liver injury due to paracetamol. The dosage of paracetamol ingested was within current guidance yet there was sudden derangement of liver function. The patient was treated with five days of N-acetyl cysteine to which he responded, with his alanine aminotransferase improving from 5,599 to 652 and international normalised ratio from 5.0 to 0.9. He had risk factors for paracetamol toxicity as he was malnourished and had muscular dystrophy. The purpose of this case report is to highlight that despite prescribing approved dosages of paracetamol some patients may have toxicity due to altered body composition and pharmacokinetics.

Fatal liver failure after therapeutic doses of paracetamol in a patient with Duchenne muscular dystrophy and atypical pharmacogenetic profile of drug-metabolizing enzymes

Paracetamol has a good safety profile, but pharmacogenetic differences in drug-metabolizing enzymes may have an impact on its risk of hepatotoxicity. We present a case of fatal acute liver failure (ALF) after therapeutic doses of paracetamol in a patient with Duchenne muscular dystrophy, where pharmacogenetic screening was conducted. This 30-year-old man was electively admitted for a tracheostomy. A total of 14.5 g paracetamol was given over four days. He developed a severe ALF and died 11 days after admission. Pharmacogenetic screening showed absent CYP2D6 metabolism and increased CYP1A2 activity, which may have increased the formation of toxic intermediate metabolite, N-acetyl-p-benzo-quinone imine (NAPQI). He also had decreased function of UGT2B15, which increases the amount of paracetamol available for metabolism to NAPQI. Having a reduced muscle mass and thus a reduced glutathione levels to detoxify produced NAPQI may add to the risk of toxicity. This case may indicate that pharmacogenetic variability is of potential relevance for the risk of paracetamol-induced hepatotoxicity in patients with neuromuscular diseases. Further studies should investigate if pharmacogenetic screening could be a tool to detect potentially increased risk of hepatotoxicity in these patients at therapeutic doses of paracetamol and hence provide information for selection of analgesic treatment.

Proteomic profiling of liver tissue from the mdx-4cv mouse model of Duchenne muscular dystrophy

Background

Duchenne muscular dystrophy is a highly complex multi-system disease caused by primary abnormalities in the membrane cytoskeletal protein dystrophin. Besides progressive skeletal muscle degeneration, this neuromuscular disorder is also associated with pathophysiological perturbations in many other organs including the liver. To determine potential proteome-wide alterations in liver tissue, we have used a comparative and mass spectrometry-based approach to study the dystrophic mdx-4cv mouse model of dystrophinopathy.

Methods

The comparative proteomic profiling of mdx-4cv versus wild type liver extracts was carried out with an Orbitrap Fusion Tribrid mass spectrometer. The distribution of identified liver proteins within protein families and potential protein interaction patterns were analysed by systems bioinformatics. Key findings on fatty acid binding proteins were confirmed by immunoblot analysis and immunofluorescence microscopy.

Results

The proteomic analysis revealed changes in a variety of protein families, affecting especially fatty acid, carbohydrate and amino acid metabolism, biotransformation, the cellular stress response and ion handling in the mdx-4cv liver. Drastically increased protein species were identified as fatty acid binding protein FABP5, ferritin and calumenin. Decreased liver proteins included phosphoglycerate kinase, apolipoprotein and perilipin. The drastic change in FABP5 was independently verified by immunoblotting and immunofluorescence microscopy.

Conclusions

The proteomic results presented here indicate that the intricate and multifaceted pathogenesis of the mdx-4cv model of dystrophinopathy is associated with secondary alterations in the liver affecting especially fatty acid transportation. Since FABP5 levels were also shown to be elevated in serum from dystrophic mice, this protein might be a useful indicator for monitoring liver changes in X-linked muscular dystrophy.

Incidence and risk factors for post-operative complications after scoliosis surgery in patients with Duchenne muscular dystrophy : a comparison with other neuromuscular conditions

We report the incidence of and risk factors for complications after scoliosis surgery in patients with Duchenne muscular dystrophy (DMD) and compare them with those of other neuromuscular conditions. We identified 110 (64 males, 46 females) consecutive patients with a neuromuscular disorder who underwent correction of the scoliosis at a mean age of 14 years (7 to 19) and had a minimum two-year follow-up. We recorded demographic and peri-operative data, including complications and re-operations. There were 60 patients with cerebral palsy (54.5%) and 26 with DMD (23.6%). The overall complication rate was 22% (24 patients), the most common of which were deep wound infection (9, 8.1%), gastrointestinal complications (5, 4.5%) and hepatotoxicity (4, 3.6%). The complication rate was higher in patients with DMD (10/26, 38.5%) than in those with other neuromuscular conditions (14/84, 16.7% (p = 0.019). All hepatotoxicity occurred in patients with DMD (p = 0.003), who also had an increased rate of deep wound infection (19% vs 5%) (p = 0.033). In the DMD group, no peri-operative factors were significantly associated with the rate of overall complications or deep wound infection. Increased intra-operative blood loss was associated with hepatotoxicity (p = 0.036). In our series, correction of a neuromuscular scoliosis had an acceptable rate of complications: patients with DMD had an increased overall rate compared with those with other neuromuscular conditions. These included deep wound infection and hepatotoxicity. Hepatotoxicity was unique to DMD patients, and we recommend peri-operative vigilance after correction of a scoliosis in this group.

Acute liver failure after recommended doses of acetaminophen in patients with myopathies

OBJECTIVE

To determine the likelihood that recommended doses of acetaminophen are associated with acute liver failure in patients with myopathies.

DESIGN

Retrospective analysis.

SETTING

Level III pediatric intensive care unit.

PATIENTS

Two pediatric patients with myopathies and acute liver failure.

CLINICAL INVESTIGATIONS

We determined acetaminophen protein adduct levels, in combination with a literature review and systematic evaluation of the cases, using the Roussel Uclaf Causality Assessment Method for drug-induced liver injury to assess causality between recommended acetaminophen dosing and acute liver failure in two children with myopathies.

MAIN RESULTS

The serum adduct levels were consistent with the values previously reported in children with acute liver injury following acetaminophen overdose. We found four similar cases of acute liver failure in pediatric and adult patients with myopathies following recommended acetaminophen doses in the literature (n = 3) and personal communication (n = 1). The Roussel Uclaf Causality Assessment Method suggested a probable relationship between acetaminophen use at recommended doses and acute liver failure in our myopathy patients.

CONCLUSION

Our data suggest that some patients with myopathies who are receiving recommended doses of acetaminophen may be at increased risk for the development of toxicity resulting in acute liver failure. More studies are needed to corroborate these findings. In the meantime, we would advise physicians to be alert in these patients while taking acetaminophen, especially when critically ill or postoperative.

Acute liver failure following therapeutic paracetamol administration in patients with muscular dystrophies

Clinically significant liver damage in patients taking therapeutic doses of paracetamol is very rare. We report two cases of fulminant hepatic failure caused by therapeutic (4 g x day(-1)) paracetamol administration on our Intensive Care Unit. Both patients had a muscular dystrophy and presented with a chest infection on a background of endstage neuromuscular respiratory failure. We also noted one further similar case in the literature and suggest a relationship between muscular dystrophy and paracetamol-induced hepatotoxicity. In this report we discuss in detail possible mechanisms that may account for this apparent association, which include altered pharmacokinetics, reduced glutathione stores, malnutrition and hypoxic injury.

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

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

CONCLUSION

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

Paracetamol pro re nata orders: an audit

OBJECTIVES

Paracetamol is used widely in hospital practice, but little is known of the details concerning prescribing practices. This study compared the prescribing habits of physicians with regard to paracetamol, pro re nata (PRN), with the nursing interpretation of the order and with evidence-based practice.

METHODS

The charts of 313 children were reviewed. An audit of 100 children, in whom paracetamol PRN had been prescribed, noted whether an indication for its use was written by the physician. The physician was asked what he/she intended the prescription to mean. The nurses who had signed for administration were asked what their indications were for giving the paracetamol. The hospital guidelines on the prescribing of paracetamol were compared to the clinical practices of the doctors and nurses.

RESULTS

Seventy-four percent of all the charts had an order for paracetamol. An audit of 100 children revealed that only one physician had provided written indications for administration of paracetamol. There were frequent miscommunications between physicians and nurses about the intention of the order for paracetamol. Nurses tended to administer paracetamol at lower temperatures than doctors had intended. In other cases, what the physician had intended as the indication for paracetamol was quite different from what the nurse understood. There were also considerable variations in interpretations within their craft groups.

CONCLUSION

What was observed in this study was idiosyncratic ordering and administration of paracetamol. It is unlikely that this problem is unique to a single hospital. The current situation needs to be addressed as a system issue, with the challenge being to develop more objective indications for the use of paracetamol, and to ensure the medical staff are more explicit in what their orders mean.

Important role of prodromal viral infections responsible for inhibition of xenobiotic metabolizing enzymes in the pathomechanism of idiopathic Reye's syndrome, Stevens-Johnson syndrome, autoimmune hepatitis, and hepatotoxicity of the therapeutic doses of acetaminophen used in genetically predisposed persons

Upper respiratory tract febrile illnesses caused by various viruses, mycoplasma, chlamydia infections, and/or inflammatory diseases are usually observed a few days to a few (several) weeks before the onset of Reye's syndrome, Stevens-Johnson syndrome, autoimmune hepatitis (hepatotropic virus infections), or hepatotoxicity associated with therapeutic administration of acetaminophen in persons with varying degrees of deficits of important enzymatic activity. Activation of systemic host defense mechanisms by inflammatory component(s) results in depression of various induced and constitutive isoforms of cytochrome P-450 mixed-function oxidase system superfamily enzymes in the liver and most other tissues of the body. Because several cytochrome P-450 enzymes activities important for biotransformation of many endogenous and egzogenous substances show considerable variability between individuals, in some genetically predisposed persons, even the administration of therapeutic doses of a drug may result in serious clinical mishaps, if an important concomitant risk factor (eg, acute viral infection) is involved. Several inflammatory cytokines, such as interleukins, transforming growth factor beta1, human hepatocyte growth factor, and lymphotoxin, downregulate gene expression of major cytochrome P-450 enzymes with the specific effects on mRNA levels, protein expression, and enzyme activity observed with a given cytokine varying for each P-450 studied, thus eventually leading to metabolite-mediated adverse drug reactions and immunometallic diseases which sometimes result in tissue injury beyond the site(s) where metabolic bioactivation takes place. On the other hand, it must be emphasized that inhibition of metabolism of several drugs, as well as influence on the concentration and/or ratio of various cytokines in inflamed tissues, may exert beneficial effects in patients with different diseases, thus opening new therapeutic possibilities. Clinically relevant interactions may be exemplified by the effects of some fluoroquinolone antibiotics, such as pefloxacin and ciprofloxacin, which probably have a steroid-sparing effect in some patients with frequently relapsing nephrotic syndrome, and an increased bioavailability of several drugs following concomitant intake with freshly pressed grapefruit juice, eventually caused by inhibition of their metabolism, mediated mainly by CYP3A and specifically inhibited by naturally occurring flavonoids.

Childhood poisoning in Queensland: an analysis of presentation and admission rates

OBJECTIVE

To determine the presentation rates for paediatric poisoning by ingestion and the determinants of hospital admission.

METHODOLOGY

Cross-sectional survey using an injury surveillance database from emergency departments in South Brisbane, Mackay and Mt Isa, Queensland, from January 1998 to December 1999. There were 1516 children aged 0-14 years who presented following ingestional poisoning.

RESULTS

The presentation rates for poisoning were 690, 40 and 67 per 100000 population aged 0-4, 5-9 and 10-14 years, respectively. The admission rates to hospital for poisoning were 144, 14 and 22 per 100000 population aged 0-4, 5-9 and 10-14 years, respectively. Although presentation rates for poisoning were higher in the rural centres the admission rates were disproportionately high for the 0-4 years age group. The agents most frequently ingested were paracetamol, Dimetapp, rodenticides and essential oils.

CONCLUSION

There is a need to design and implement interventions aimed at reducing poison exposures and unnecessary hospital admissions in the 0-4 years age group.

The pharmacological basis of contemporary pain management

Pain management has become an increasingly well researched area in medicine over recent years, and there have been advances in a number of areas. While opioids remain an integral part of pain-management strategies, there is now an emphasis on the use of adjuvant drugs, such as paracetamol and anti-inflammatory agents, which through physiological or pharmacological synergism, both enhance pain control and reduce opioid use. The management of neuropathic pain continues to be a challenge. Anti-epileptics and antidepressants, together with clonidine and ketamine, provide the foundations for treatment. Another area of interest has been the widespread use of patient-controlled analgesia and the administration of some drugs, especially opioids, by means other than traditional oral and parenteral routes. The number of new drugs that have reached the stage of clinical trials has been small, yet they offer exciting possibilities. The epibatidine analogue ABT-594 and zinconitide both offer novel approaches to the management of neuropathic pain states, while selective cyclo-oxygenase-2 inhibitors and nitroaspirins may see advances in the management of nociceptive pain states.