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Chiew AL, Isbister GK. Advances in the understanding of acetaminophen toxicity mechanisms: a clinical toxicology perspective. Expert Opin Drug Metab Toxicol 2023; 19:601-616. [PMID: 37714812 DOI: 10.1080/17425255.2023.2259787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 08/02/2023] [Accepted: 09/13/2023] [Indexed: 09/17/2023]
Abstract
INTRODUCTION Acetaminophen (paracetamol) is a commonly used analgesic and antipyretic agent, which is safe in therapeutic doses. Acetaminophen poisoning due to self-harm or repeated supratherapeutic ingestion is a common cause of acute liver injury. Acetylcysteine has been a mainstay of treatment for acetaminophen poisoning for decades and is efficacious if administered early. However, treatment failures occur if administered late, in 'massive' overdoses or in high-risk patients. AREAS COVERED This review provides an overview of the mechanisms of toxicity of acetaminophen poisoning (metabolic and oxidative phase) and how this relates to the assessment and treatment of the acetaminophen poisoned patient. The review focuses on how these advances offer further insight into the utility of novel biomarkers and the role of proposed adjunct treatments. EXPERT OPINION Advances in our understanding of acetaminophen toxicity have allowed the development of novel biomarkers and a better understanding of how adjunct treatments may prevent acetaminophen toxicity. Newly proposed adjunct treatments like fomepizole are being increasingly used without robust clinical trials. Novel biomarkers (not yet clinically available) may provide better assessment of these newly proposed adjunct treatments, particularly in clinical trials. These advances in our understanding of acetaminophen toxicity and liver injury hold promise for improved diagnosis and treatment.
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Affiliation(s)
- Angela L Chiew
- Department of Clinical Toxicology, Prince of Wales Hospital, Randwick, NSW, Australia
- Faculty of Medicine, The University of New South Wales, Sydney, New South Wales, Australia
- New South Wales Poisons Information Centre, Sydney Children's Hospital, Sydney, New South Wales, Australia
| | - Geoffrey K Isbister
- New South Wales Poisons Information Centre, Sydney Children's Hospital, Sydney, New South Wales, Australia
- Clinical Toxicology Research Group, University of Newcastle, Callaghan, NSW, Australia
- Department of Clinical Toxicology, Calvary Mater Newcastle, Waratah, NSW, Australia
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Chiew AL, Isbister GK, Stathakis P, Isoardi KZ, Page C, Ress K, Chan BS, Buckley NA. Acetaminophen Metabolites on Presentation Following an Acute Acetaminophen Overdose (ATOM-7). Clin Pharmacol Ther 2023; 113:1304-1314. [PMID: 36919638 PMCID: PMC10952325 DOI: 10.1002/cpt.2888] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 03/09/2023] [Indexed: 03/16/2023]
Abstract
Acetaminophen (APAP) is commonly taken in overdose and can cause acute liver injury via the toxic metabolite NAPQI formed by cytochrome (CYP) P450 pathway. We aimed to evaluate the concentrations of APAP metabolites on presentation following an acute APAP poisoning and whether these predicted the subsequent onset of hepatotoxicity (peak alanine aminotransferase > 1,000 U/L). The Australian Toxicology Monitoring (ATOM) study is a prospective observational study, recruiting via two poison information centers and four toxicology units. Patients following an acute APAP ingestion presenting < 24 hours post-ingestion were recruited. Initial samples were analyzed for APAP metabolites, those measured were the nontoxic glucuronide (APAP-Glu) and sulfate (APAP-Sul) conjugates and NAPQI (toxic metabolite) conjugates APAP-cysteine (APAP-Cys) and APAP-mercapturate (APAP-Mer). The primary outcome was hepatotoxicity. In this study, 200 patients were included, with a median ingested dose of 20 g, 191 received acetylcysteine at median time of 5.8 hours post-ingestion. Twenty-six patients developed hepatotoxicity, one had hepatotoxicity on arrival (excluded from analysis). Those who developed hepatotoxicity had significantly higher total CYP metabolite concentrations: (36.8 μmol/L interquartile range (IQR): 27.8-51.7 vs. 10.8 μmol/L IQR: 6.9-19.5) and these were a greater proportion of total metabolites (5.4%, IQR: 3.8-7.7) vs. 1.7%, IQR: 1.3-2.6, P < 0.001)]. Furthermore, those who developed hepatotoxicity had lower APAP-Sul concentrations (49.1 μmol/L, IQR: 24.7-72.2 vs. 78.7 μmol/L, IQR: 53.6-116.4) and lower percentage of APAP-Sul (6.3%, IQR: 4.6-10.9 vs. 13.1%, IQR, 9.1-20.8, P < 0.001)]. This study found that those who developed hepatotoxicity had higher APAP metabolites derived from CYP pathway and lower sulfation metabolite on presentation. APAP metabolites may be utilized in the future to identify patients who could benefit from increased acetylcysteine or newer adjunct or research therapies.
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Affiliation(s)
- Angela L. Chiew
- Department of Clinical ToxicologyPrince of Wales HospitalRandwickNew South WalesAustralia
- Faculty of MedicineThe University of New South WalesSydneyNew South WalesAustralia
- New South Wales Poisons Information CentreSydney Children's HospitalSydneyNew South WalesAustralia
| | - Geoffrey K. Isbister
- New South Wales Poisons Information CentreSydney Children's HospitalSydneyNew South WalesAustralia
- Department of Clinical Toxicology and Pharmacology, Calvary Mater Newcastle and School of Medical PracticeUniversity of NewcastleCallaghanNew South WalesAustralia
| | - Paul Stathakis
- NSW Health PathologyPrince of Wales HospitalRandwickNew South WalesAustralia
| | - Katherine Z. Isoardi
- Clinical Toxicology UnitPrincess Alexandra HospitalBrisbaneQueenslandAustralia
- Queensland Poisons Information CentreQueensland Children's HospitalBrisbaneQueenslandAustralia
| | - Colin Page
- Clinical Toxicology UnitPrincess Alexandra HospitalBrisbaneQueenslandAustralia
- Queensland Poisons Information CentreQueensland Children's HospitalBrisbaneQueenslandAustralia
| | - Kirsty Ress
- NSW Health PathologyPrince of Wales HospitalRandwickNew South WalesAustralia
| | - Betty S.H. Chan
- Department of Clinical ToxicologyPrince of Wales HospitalRandwickNew South WalesAustralia
- Faculty of MedicineThe University of New South WalesSydneyNew South WalesAustralia
- New South Wales Poisons Information CentreSydney Children's HospitalSydneyNew South WalesAustralia
| | - Nicholas A. Buckley
- New South Wales Poisons Information CentreSydney Children's HospitalSydneyNew South WalesAustralia
- Discipline of Biomedical Informatics and Digital HealthThe University of SydneySydneyNew South WalesAustralia
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du Preez HN, Aldous C, Kruger HG, Johnson L. N-Acetylcysteine and Other Sulfur-Donors as a Preventative and Adjunct Therapy for COVID-19. Adv Pharmacol Pharm Sci 2022; 2022:4555490. [PMID: 35992575 PMCID: PMC9385285 DOI: 10.1155/2022/4555490] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 07/07/2022] [Indexed: 12/11/2022] Open
Abstract
The airway epithelial glycocalyx plays an important role in preventing severe acute respiratory syndrome coronavirus 2 entry into the epithelial cells, while the endothelial glycocalyx contributes to vascular permeability and tone, as well as modulating immune, inflammatory, and coagulation responses. With ample evidence in the scientific literature that coronavirus disease 2019 (COVID-19) is related to epithelial and endothelial dysfunction, preserving the glycocalyx should be the main focus of any COVID-19 treatment protocol. The most studied functional unit of the glycocalyx is the glycosaminoglycan heparan sulfate, where the degree and position of the sulfate groups determine the biological activity. N-acetylcysteine (NAC) and other sulfur donors contribute to the inorganic sulfate pool, the rate-limiting molecule in sulfation. NAC is not only a precursor to glutathione but also converts to hydrogen sulfide, inorganic sulfate, taurine, Coenzyme A, and albumin. By optimising inorganic sulfate availability, and therefore sulfation, it is proposed that COVID-19 can be prevented or at least most of the symptoms attenuated. A comprehensive COVID-19 treatment protocol is needed to preserve the glycocalyx in both the prevention and treatment of COVID-19. The use of NAC at a dosage of 600 mg bid for the prevention of COVID-19 is proposed, but a higher dosage of NAC (1200 mg bid) should be administered upon the first onset of symptoms. In the severe to critically ill, it is advised that IV NAC should be administered immediately upon hospital admission, and in the late stage of the disease, IV sodium thiosulfate should be considered. Doxycycline as a protease inhibitor will prevent shedding and further degradation of the glycocalyx.
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Affiliation(s)
- Heidi N du Preez
- Catalysis and Peptide Research Unit, University of KwaZulu-Natal, Westville Campus, Durban, South Africa
| | - Colleen Aldous
- College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Hendrik G Kruger
- Catalysis and Peptide Research Unit, University of KwaZulu-Natal, Westville Campus, Durban, South Africa
| | - Lin Johnson
- School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa
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du Preez HN, Aldous C, Hayden MR, Kruger HG, Lin J. Pathogenesis of COVID-19 described through the lens of an undersulfated and degraded epithelial and endothelial glycocalyx. FASEB J 2021; 36:e22052. [PMID: 34862979 DOI: 10.1096/fj.202101100rr] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 11/04/2021] [Accepted: 11/08/2021] [Indexed: 12/13/2022]
Abstract
The glycocalyx surrounds every eukaryotic cell and is a complex mesh of proteins and carbohydrates. It consists of proteoglycans with glycosaminoglycan side chains, which are highly sulfated under normal physiological conditions. The degree of sulfation and the position of the sulfate groups mainly determine biological function. The intact highly sulfated glycocalyx of the epithelium may repel severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) through electrostatic forces. However, if the glycocalyx is undersulfated and 3-O-sulfotransferase 3B (3OST-3B) is overexpressed, as is the case during chronic inflammatory conditions, SARS-CoV-2 entry may be facilitated by the glycocalyx. The degree of sulfation and position of the sulfate groups will also affect functions such as immune modulation, the inflammatory response, vascular permeability and tone, coagulation, mediation of sheer stress, and protection against oxidative stress. The rate-limiting factor to sulfation is the availability of inorganic sulfate. Various genetic and epigenetic factors will affect sulfur metabolism and inorganic sulfate availability, such as various dietary factors, and exposure to drugs, environmental toxins, and biotoxins, which will deplete inorganic sulfate. The role that undersulfation plays in the various comorbid conditions that predispose to coronavirus disease 2019 (COVID-19), is also considered. The undersulfated glycocalyx may not only increase susceptibility to SARS-CoV-2 infection, but would also result in a hyperinflammatory response, vascular permeability, and shedding of the glycocalyx components, giving rise to a procoagulant and antifibrinolytic state and eventual multiple organ failure. These symptoms relate to a diagnosis of systemic septic shock seen in almost all COVID-19 deaths. The focus of prevention and treatment protocols proposed is the preservation of epithelial and endothelial glycocalyx integrity.
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Affiliation(s)
- Heidi N du Preez
- Catalysis and Peptide Research Unit, University of KwaZulu-Natal, Durban, South Africa
| | - Colleen Aldous
- College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Melvin R Hayden
- Division of Endocrinology Diabetes and Metabolism, Department of Internal Medicine, University of Missouri-Columbia School of Medicine, Columbia, Missouri, USA.,Diabetes and Cardiovascular Disease Center, University of Missouri-Columbia School of Medicine, Columbia, Missouri, USA
| | - Hendrik G Kruger
- Catalysis and Peptide Research Unit, University of KwaZulu-Natal, Durban, South Africa
| | - Johnson Lin
- School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa
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Li J, Chiew AL, Isbister GK, Duffull SB. Sulfate conjugation may be the key to hepatotoxicity in paracetamol overdose. Br J Clin Pharmacol 2020; 87:2392-2396. [DOI: 10.1111/bcp.14642] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 10/25/2020] [Accepted: 11/05/2020] [Indexed: 11/30/2022] Open
Affiliation(s)
- Jingyun Li
- School of Pharmacy University of Otago Dunedin New Zealand
| | - Angela L. Chiew
- Emergency Department and Clinical Toxicology Prince of Wales Hospital and Community Health Services Randwick Australia
- Department of Pharmacology, School of Medical Sciences University of Sydney Sydney Australia
- NSW Poisons Information Centre Children's Hospital at Westmead Westmead Australia
| | - Geoffrey K. Isbister
- NSW Poisons Information Centre Children's Hospital at Westmead Westmead Australia
- Clinical Toxicology Research Group University of Newcastle Newcastle Australia
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Zamek-Gliszczynski MJ, Hoffmaster KA, Nezasa KI, Tallman MN, Brouwer KLR. Integration of hepatic drug transporters and phase II metabolizing enzymes: Mechanisms of hepatic excretion of sulfate, glucuronide, and glutathione metabolites. Eur J Pharm Sci 2006; 27:447-86. [PMID: 16472997 DOI: 10.1016/j.ejps.2005.12.007] [Citation(s) in RCA: 187] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Accepted: 12/06/2005] [Indexed: 12/12/2022]
Abstract
The liver is the primary site of drug metabolism in the body. Typically, metabolic conversion of a drug results in inactivation, detoxification, and enhanced likelihood for excretion in urine or feces. Sulfation, glucuronidation, and glutathione conjugation represent the three most prevalent classes of phase II metabolism, which may occur directly on the parent compounds that contain appropriate structural motifs, or, as is usually the case, on functional groups added or exposed by phase I oxidation. These three conjugation reactions increase the molecular weight and water solubility of the compound, in addition to adding a negative charge to the molecule. As a result of these changes in the physicochemical properties, phase II conjugates tend to have very poor membrane permeability, and necessitate carrier-mediated transport for biliary or hepatic basolateral excretion into sinusoidal blood for eventual excretion into urine. This review summarizes sulfation, glucuronidation, and glutathione conjugation reactions, as well as recent progress in elucidating the hepatic transport mechanisms responsible for the excretion of these conjugates from the liver. The discussion focuses on alterations of metabolism and transport by chemical modulators, and disease states, as well as pharmacodynamic and toxicological implications of hepatic metabolism and/or transport modulation for certain active phase II conjugates. A brief discussion of issues that must be considered in the design and interpretation of phase II metabolite transport studies follows.
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