DOCSLIB.ORG

Does Cytochrome P450 Liver Isoenzyme Induction Increase the Risk of Liver Toxicity After Paracetamol Overdose?

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Does Cytochrome P450 Liver Isoenzyme Induction Increase the Risk of Liver Toxicity After Paracetamol Overdose? Open Access Emergency Medicine Dovepress open access to scientific and medical research Open Access Full Text Article REVIEW Does cytochrome P450 liver isoenzyme induction increase the risk of liver toxicity after paracetamol overdose? Sarbjeet S Kalsi1,2 Abstract: Paracetamol (acetaminophen, N-acetyl-p-aminophenol, 4-hydroxyacetanilide) David M Wood2–4 is the most common cause of acute liver failure in developed countries. There are a number W Stephen Waring5 of factors which potentially impact on the risk of an individual developing hepatotoxicity Paul I Dargan2–4 following an acute paracetamol overdose. These include the dose of paracetamol ingested, time to presentation, decreased liver glutathione, and induction of cytochrome P450 (CYP) 1Emergency Department, 2Clinical Toxicology, Guy’s and St Thomas’ isoenzymes responsible for the metabolism of paracetamol to its toxic metabolite N-acetyl- NHS Foundation Trust, London; p-benzoquinoneimine (NAPQI). In this paper, we review the currently published literature to 3 King’s Health Partners, determine whether induction of relevant CYP isoenzymes is a risk factor for hepatotoxicity in 4King’s College London, London; 5York Teaching Hospital NHS patients with acute paracetamol overdose. Animal and human in vitro studies have shown that For personal use only. Foundation Trust, York, UK the CYP isoenzyme responsible for the majority of human biotransformation of paracetamol to NAPQI is CYP2E1 at both therapeutic and toxic doses of paracetamol. Current UK treatment guidelines suggest that patients who use a number of drugs therapeutically should be treated as “high-risk” after paracetamol overdose. However, based on our review of the available litera- ture, it appears that the only drugs for which there is evidence of the potential for an increased risk of hepatotoxicity associated with paracetamol overdose are phenobarbital, primidone, isoniazid, and perhaps St John’s wort. There is no evidence that other drugs often quoted as increasing risk, such as carbamazepine, phenytoin, primidone, rifampicin, rifabutin, efavirenz, or nevirapine, should be considered risk factors for hepatotoxicity in patients presenting with acute paracetamol overdose. Keywords: paracetamol, overdose, hepatotoxicity, isoenzymes Open Access Emergency Medicine downloaded from https://www.dovepress.com/ by 137.108.70.13 on 14-May-2019 Background Paracetamol (acetaminophen, N-acetyl-p-aminophenol, 4-hydroxyacetanilide) overdose causing fatal hepatotoxicity was first reported in humans in 1966.1,2 Since then, paracetamol poisoning has become the most common cause of acute liver failure in many developed countries/regions, including the UK, US, Canada, Australia, and Scandinavia.3–7 Paracetamol poisoning may result from either an acute overdose (where the drug is ingested at a single point in time, usually within one hour), or as a staggered supratherapeutic ingestion over a longer period. This article will focus on Correspondence: David Wood single-ingestion paracetamol poisoning. Medical Toxicology Office, A number of factors are important in determining the risk of toxicity after Bermondsey Wing, Guy’s Hospital, paracetamol poisoning, and these influence the decision to administer antidotal Great Maze Pond, London, SE1 9RT, United Kingdom treatment with N-acetylcysteine.8–13 The plasma paracetamol concentration plotted Tel +44 20 7188 5848 against time after ingestion is compared with a “treatment line” to determine the need Fax +44 20 7188 1289 Email [email protected] for antidotal therapy. There are a number of different treatment lines used around submit your manuscript | www.dovepress.com Open Access Emergency Medicine 2011:3 69–76 69 Dovepress © 2011 Kalsi et al, publisher and licensee Dove Medical Press Ltd. This is an Open Access article http://dx.doi.org/10.2147/OAEM.S24962 which permits unrestricted noncommercial use, provided the original work is properly cited. Powered by TCPDF (www.tcpdf.org) 1 / 1 Kalsi et al Dovepress the world.11–13 In addition, in the UK, there are currently two or death.27,28 An aspartate aminotransferase or alanine ami- treatment lines, ie, one for those deemed to be at usual risk notransferase exceeding 1000 IU/L is generally associated of paracetamol-related hepatotoxicity, and a lower line used with histological changes of centrilobular necrosis of varying for those deemed to be at “high” risk of paracetamol-related severity.29,30 However, for most patients, these changes are hepatotoxicity.9,13,14 Common factors used to determine risk fully reversible, leading to recovery without any long-term of paracetamol-related hepatotoxicity include depletion of damage.29,30 liver glutathione (eg, malnutrition, eating disorders) and Based on data from patients presenting with paraceta- induction of liver cytochrome P450 (CYP) 2E1 (eg, chronic mol poisoning prior to the introduction of antidotal therapy, ethanol use, phenytoin, or other enzyme-inducing drugs). In Prescott reported that up to 25% of those with severe amin- the UK, the process of determining which treatment line to otransferase-defined hepatotoxicity died.31 This means that base treatment on following a single-time point paracetamol even without N-acetylcysteine, more than 75% of severely overdose is known as “risk stratification”. This relies on both poisoned patients will recover fully. Therefore, although aspar- laboratory measurement of paracetamol concentration and tate aminotransferase or alanine aminotransferase are used assessment of the patient history to determine the interval to define paracetamol-related hepatotoxicity, a combination after ingestion, which appears to be reasonably reliable in of International Normalised Ratio (INR), plasma creatinine, this patient population.15,16 In addition to determining the metabolic acidosis, and clinical factors, such as the presence need for treatment, clinicians need to consider the potential of encephalopathy, are more reliable at selecting patients who for adverse reactions to the antidote. will either die or require hepatic transplantation.32,33 Mechanism of paracetamol-related Factors reported to be associated hepatotoxicity with increased risk The parent paracetamol molecule is not in itself associated There are a number of factors which potentially impact on with toxicity.17 At therapeutic doses, paracetamol is predomi- the risk of an individual developing hepatotoxicity following For personal use only. nantly metabolized by hepatic sulfation and glucuronidation, an acute paracetamol overdose. These can be broadly divided with less than 5%–10% being metabolized by the hepatic into the following categories: dose of paracetamol ingested; CYP system (predominantly CYP2E1 and CYP3A4) to time from ingestion to treatment with N-acetylcysteine; N-acetyl-p-benzoquinoneimine (NAPQI), a highly reactive increased metabolism of paracetamol to NAPQI due to intermediate metabolite responsible for paracetamol-related induction of the relevant CYP isoenzymes; and reduction hepatotoxicity.18–20 At therapeutic doses of paracetamol, this in liver glutathione stores. In this paper, we will review metabolite is effectively detoxified by reduced glutathione the evidence for increased risk of hepatotoxicity following into cysteine and mercapturic conjugates which are renally paracetamol overdose due to CYP isoenzyme induction excreted.21 Following a supratherapeutic dose or overdose of unrelated to ethanol. paracetamol, glucuronidation/sulfation conjugation pathways are saturated, and therefore a greater proportion of paraceta- Evidence for induction of CYP Open Access Emergency Medicine downloaded from https://www.dovepress.com/ by 137.108.70.13 on 14-May-2019 mol is metabolized to NAPQI.22–24 Intrahepatic glutathione isoenzyme system stores may be insufficient to detoxify the greater NAPQI, and As discussed in the introduction, the toxic metabolite of when glutathione concentrations fall to approximately 30% paracetamol is NAPQI, and this is formed by oxidative metab- of normal, NAPQI covalently binds to hepatic cells.21 This olism via the CYP system.17–20,34 This system is subdivided into is associated with irreversible hepatocellular necrosis which, multiple isoenzyme groups with different substrate specificity. in severe cases, results in liver transplant or death.14 Animal studies in the 1970s demonstrated that paracetamol is metabolized by the CYP system.17,18 More recent inves- Definition of paracetamol-related tigations have centered on which isoenzyme(s) metabolize hepatotoxicity paracetamol, and the CYP1A2, CYP2A6, CYP2D6, CYP2E1, Paracetamol-induced hepatotoxicity is classically defined as and CYP3A4 isoenzymes have all been investigated.35–43 an aspartate aminotransferase or alanine aminotransferase The published literature is largely based on in vitro and ani- rise to over 1000 IU/L.25,26 Patients without an aminotrans- mal models, with very few human studies in vivo. We will ferase elevation do not go on to experience acute liver now summarize the available literature on the relative impor- injury and therefore are not at risk of acute liver failure tance of these isoenzymes for paracetamol metabolism. 70 submit your manuscript | www.dovepress.com Open Access Emergency Medicine 2011:3 Dovepress Powered by TCPDF (www.tcpdf.org) 1 / 1 Dovepress CYP induction and liver toxicity CYP1A2 enhanced paracetamol-induced hepatotoxicity following An in vitro study of IgG-mediated inhibition of CYP1A2 overdose.47 However, two separate human volunteer studies and CYP2E1
Load more

Recommended publications
  • Cheminformatics Tools for Enabling Metabolomics by Yannick Djoumbou Feunang
    Cheminformatics Tools for Enabling Metabolomics by Yannick Djoumbou Feunang A thesis submitted in partial fulfillment of requirements for the degree of Doctor of Philosophy in Microbiology and Biotechnology Department of Biological Sciences University of Alberta ©Yannick Djoumbou Feunang, 2017 ii Abstract Metabolites are small molecules (<1500 Da) that are used in or produced during chemical reactions in cells, tissues, or organs. Upon absorption or biosynthesis in humans (or other organisms), they can either be excreted back into the environment in their original form, or as a pool of degradation products. The outcome and effects of such interactions is function of many variables, including the structure of the starting metabolite, and the genetic disposition of the host organism. For this reasons, it is usually very difficult to identify the transformation products as well as their long-term effect in humans and the environment. This can be explained by many factors: (1) the relevant knowledge and data are for the most part unavailable in a publicly available electronic format; (2) when available, they are often represented using formats, vocabularies, or schemes that vary from one source (or repository) to another. Assuming these issues were solved, detecting patterns that link the metabolome to a specific phenotype (e.g. a disease state), would still require that the metabolites from a biological sample be identified and quantified, using metabolomic approaches. Unfortunately, the amount of compounds with publicly available experimental data (~20,000) is still very small, compared to the total number of expected compounds (up to a few million compounds). For all these reasons, the development of cheminformatics tools for data organization and mapping, as well as for the prediction of biotransformation and spectra, is more crucial than ever.
    [Show full text]
  • Exposure to Acetaminophen and All Its Metabolites Upon 10, 15, and 20Mg/Kg Intravenous Acetaminophen in Very-Preterm Infants
    Articles | Clinical Investigation nature publishing group Exposure to acetaminophen and all its metabolites upon 10, 15, and 20mg/kg intravenous acetaminophen in very-preterm infants Robert B. Flint1,2,3,11, Daniella W. Roofthooft1,11,AnnevanRongen4,5, Richard A. van Lingen6, Johannes N. van den Anker7,8,9, Monique van Dijk1,7, Karel Allegaert1,7,10, Dick Tibboel7, Catherijne A.J. Knibbe4,5 and Sinno H.P. Simons1 BACKGROUND: Exposure to acetaminophen and its meta- acetaminophen as an opioid-sparing therapy in adults and bolites in very-preterm infants is partly unknown. We children has now been introduced in neonatal intensive care investigated the exposure to acetaminophen and its meta- units across the globe (4). However, only very limited data of bolites upon 10, 15, or 20 mg/kg intravenous acetaminophen its use are available in the most preterm infants (5,6). in preterm infants. Acetaminophen (N-acetyl-p-amino-phenol) is extensively METHODS: In a randomized trial, 59 preterm infants metabolized in the liver. The main pathways involved are (24–32 weeks’ gestational age, postnatal age o1 week) glucuronidation and sulfation, which in adults account for received 10, 15, or 20 mg/kg acetaminophen intravenously. ~ 55 and 30% of acetaminophen metabolism, respectively Plasma concentrations of acetaminophen and its metabolites (7–9) (Figure 1). Only 2–5% is excreted unchanged in the (glucuronide, sulfate, cysteine, mercapturate, and glutathione) urine. Approximately 5–10% of acetaminophen is metabo- were determined in 293 blood samples. Area under the lized by cytochrome P450 (CYP), primarily by the CYP2E1 – plasma concentration time curves (AUC0–500 min) was related enzyme (10–12), to the toxic metabolite N-acetyl-p-benzo- to dose and gestational age.
    [Show full text]
  • The Effect of 4-Methylpyrazole on Oxidative Metabolism of Acetaminophen in Human Volunteers
    Journal of Medical Toxicology (2020) 16:169–176 https://doi.org/10.1007/s13181-019-00740-z ORIGINAL ARTICLE The Effect of 4-Methylpyrazole on Oxidative Metabolism of Acetaminophen in Human Volunteers A. Min Kang1,2 & Angela Padilla-Jones2 & Erik S. Fisher2 & Jephte Y. Akakpo3 & Hartmut Jaeschke3 & Barry H. Rumack4 & Richard D. Gerkin2 & Steven C. Curry1,2 Received: 12 July 2019 /Revised: 12 September 2019 /Accepted: 15 September 2019 /Published online: 25 November 2019 # American College of Medical Toxicology 2019 Abstract Introduction Acetaminophen (APAP) is commonly ingested in both accidental and suicidal overdose. Oxidative metabolism by cytochrome P450 2E1 (CYP2E1) produces the hepatotoxic metabolite, N-acetyl-p-benzoquinone imine. CYP2E1 inhibition using 4-methylpyrazole (4-MP) has been shown to prevent APAP-induced liver injury in mice and human hepatocytes. This study was conducted to assess the effect of 4-MP on APAP metabolism in humans. Methods This crossover trial examined the ability of 4-MP to inhibit CYP2E1 metabolism of APAP in five human volunteers. Participants received a single oral dose of APAP 80 mg/kg, both with and without intravenous 4-MP, after which urinary and plasma oxidative APAP metabolites were measured. The primary outcome was the fraction of ingested APAP excreted as total oxidative metabolites (APAP-CYS, APAP-NAC, APAP-GSH). Results Compared with APAP alone, co-treatment with 4-MP decreased the percentage of ingested APAP recovered as oxidative metabolites in 24-hour urine from 4.48 to 0.51% (95% CI = 2.31–5.63%, p = 0.003). Plasma concentrations of these oxidative metabolites also decreased.
    [Show full text]
  • A3: Antidotes in Depth
    A3: Antidotes in Depth Robert G. Hendrickson; Mary Ann Howland INTRODUCTION N-acetylcysteine (NAC) is the cornerstone of therapy for patients with potentially lethal acetaminophen (APAP) overdoses. If administered early, NAC can then prevent APAP induced hepatotoxicity. If administered after the onset of hepatotoxicity, NAC improves outcomes and decreases mortality. NAC may also limit hepatotoxicity from other xenobiotics that result in glutathione depletion and free radical formation, such as cyclopeptide- containing mushrooms, carbon tetrachloride, chloroform, pennyroyal oil, clove oil, and possibly liver failure from chronic valproic acid use.31 Finally, NAC may be useful in the management of adults with fulminant hepatic failure caused by nontoxicologic etiologies.20,75,81,84,149 HISTORY Shortly after the first case of APAP hepatotoxicity was reported, Mitchell described the protective effect of glutathione.97,127 Prescott113 first suggested NAC for APAP poisoning in 1974. Early experiments demonstrated that NAC could prevent APAP-induced hepatotoxicity in mice and that the oral (PO) and intravenous (IV) routes were equally efficacious when treatment was initiated early after ingestion.106 Several groups96,112,113,126 performed human research with oral and IV NAC in the 1970s. The US Food and Drug Administration (FDA) approved NAC for oral use in 1985 and for IV use in 2004. PHARMACOLOGY Chemistry NAC is a thiol containing (R-SH) compound that is deacetylated to cysteine, an amino acid used intracellularly. The amino acids cysteine glycine and glutamate are used to synthesize glutathione.123 Related Xenobiotics Cysteamine, methionine, and NAC, which are all glutathione precursors or substitutes, have been used successfully to prevent hepatotoxicity, but cysteamine and methionine both produce more adverse effects than NAC, and methionine is less effective than NAC.
    [Show full text]
  • Host-Microbial Interactions in the Metabolism of Therapeutic and Diet-Derived Xenobiotics
    Host-microbial interactions in the metabolism of therapeutic and diet-derived xenobiotics Rachel N. Carmody, Peter J. Turnbaugh J Clin Invest. 2014;124(10):4173-4181. https://doi.org/10.1172/JCI72335. Review Our associated microbial communities play a critical role in human health and predisposition to disease, but the degree to which they also shape therapeutic interventions is not well understood. Here, we integrate results from classic and current studies of the direct and indirect impacts of the gut microbiome on the metabolism of therapeutic drugs and diet- derived bioactive compounds. We pay particular attention to microbial influences on host responses to xenobiotics, adding to the growing consensus that treatment outcomes reflect our intimate partnership with the microbial world, and providing an initial framework from which to consider a more comprehensive view of pharmacology and nutrition. Find the latest version: https://jci.me/72335/pdf The Journal of Clinical Investigation REVIEW SERIES: GUT MICROBIOME Series Editor: Martin J. Blaser Host-microbial interactions in the metabolism of therapeutic and diet-derived xenobiotics Rachel N. Carmody and Peter J. Turnbaugh FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts, USA. Our associated microbial communities play a critical role in human health and predisposition to disease, but the degree to which they also shape therapeutic interventions is not well understood. Here, we integrate results from classic and current studies of the direct and indirect impacts of the gut microbiome on the metabolism of therapeutic drugs and diet-derived bioactive compounds. We pay particular attention to microbial influences on host responses to xenobiotics, adding to the growing consensus that treatment outcomes reflect our intimate partnership with the microbial world, and providing an initial framework from which to consider a more comprehensive view of pharmacology and nutrition.
    [Show full text]
  • Reduced Acetaminophen-Induced Liver Injury in Mice by Genetic Disruption of IL-1 Receptor Antagonist
    Laboratory Investigation (2009) 89, 68–79 & 2009 USCAP, Inc All rights reserved 0023-6837/09 $32.00 Reduced acetaminophen-induced liver injury in mice by genetic disruption of IL-1 receptor antagonist Takuya Ishibe1,2,*, Akihiko Kimura1,*, Yuko Ishida1, Tatsunori Takayasu3, Takahito Hayashi1, Koichi Tsuneyama4, Kouji Matsushima5, Ikuhiro Sakata2, Naofumi Mukaida6 and Toshikazu Kondo1 Acetaminophen (APAP) induced increases in intrahepatic expression of interleukin (IL)-1a, IL-1b, and IL-1 receptor antagonist (IL-1ra), when administered intraperitoneally. These observations prompted us to define the pathophysiological roles of IL-1ra in APAP-induced liver injury. Compared with wild-type (WT) mouse-derived hepatocytes, IL-1ra-deficient (IL-1ra KO)-derived hepatocytes exhibited more resistance against APAP but not APAP-derived major toxic metabolite, N-acetyl-p-benzoquinone imine (NAPQI). Moreover, the amounts of a major APAP adduct (selenium-binding protein), an indicator of NAPQI generation from APAP, was significantly lower in IL-1ra KO mice than WT mice with depressed intrahepatic expression of CYP1A2, CYP2E1, and CYP3A11, the enzymes crucially involved in NAPQI generation from APAP. These observations would indicate that IL-1ra deficiency impaired APAP metabolism. IL-1a and IL-1b were expressed to similar extents in livers of untreated IL-1ra KO and WT mice. By contrast, the intranuclear amount of p65 of NF-kB, which can suppress the gene expression of CYP1A2, CYP2E1, and CYP3A11, was higher in untreated IL-1ra KO than WT mice. Moreover, when mice were intraperitoneally administered APAP (200 mg/kg), IL-1ra KO mice exhibited attenuated APAP-induced liver injury as evidenced by reductions in serum alanine transferase levels and histopatholo- gical changes such as centrilobular necrosis, hemorrhages, and leukocyte infiltration.
    [Show full text]
  • Hepatocyte Circadian Clock Controls Acetaminophen Bioactivation Through NADPH-Cytochrome P450 Oxidoreductase
    Hepatocyte circadian clock controls acetaminophen bioactivation through NADPH-cytochrome P450 oxidoreductase Brian P. Johnsona, Jacqueline A. Walissera, Yan Liua, Anna L. Shena, Erin L. McDearmonb,c, Susan M. Morana, Brian E. McIntosha, Aaron L. Vollratha, Andrew C. Schookb,c, Joseph S. Takahashid,e,1, and Christopher A. Bradfielda,1 aMcArdle Laboratory for Cancer Research, University of Wisconsin, Madison, WI 53792; bDepartment of Neurobiology and cHoward Hughes Medical Institute, Northwestern University, Evanston, IL 60208; and dDepartment of Neuroscience and eHoward Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390 Contributed by Joseph S. Takahashi, November 13, 2014 (sent for review September 28, 2012; reviewed by Xinxin Ding, Garret A. FitzGerald, and Hitoshi Okamura) The diurnal variation in acetaminophen (APAP) hepatotoxicity (11,12).Collectively,thesedatahaveledtotheideathat (chronotoxicity) reportedly is driven by oscillations in metabolism feeding- and fasting-driven oscillations in glutathione and the that are influenced by the circadian phases of feeding and fasting. cytochromes P450 are major determinants of APAP chronotox- To determine the relative contributions of the central clock and the icity in the liver. hepatocyte circadian clock in modulating the chronotoxicity of In mammals, circadian physiology is directed by the tran- APAP, we used a conditional null allele of brain and muscle Arnt- scription factors CLOCK and BMAL1 (aka MOP3, ARNTL) like 1 (Bmal1, aka Mop3 or Arntl) allowing deletion of the clock (13). These molecular clock components control transcriptional from hepatocytes while keeping the central and other peripheral and translational feedback loops that guide the circadian ex- clocks (e.g., the clocks controlling food intake) intact.
    [Show full text]
  • Induced Acute Liver Failure
    Original Article Evaluation of Recent Updates Regarding Acetaminophen- Induced Acute Liver Failure Muath Atallah Albalawi1*, Saeed Awadh Albalawi1, Turki Hamdan S Albalawi1, Khalid Sulaiman Almuhawwis2, Abdullah Mansour Alswilem2, Mujahid Fahad Aldakhil2, Yasser Waleed Asiri2, Abdullah Khalid Alruwaili2, Abdullah Abdulrahman Almannaa2, Mansour Saeed Alharith3 1 Department of Medical Science, Faculty of Medicine, University of Tabuk, Tabuk, Saudi Arabia. 2 Department of Medical Science, Faculty of Medicine, Almaarefa University, Riyadh, Saudi Arabia. 3Department of Medical Science, Faculty of Medicine, King Khalid University, Abha, Saudi Arabia. Abstract Acetaminophen is considered as the most common analgesic and antipyretic over-the-counter drug. It is also considered a very safe medication if used in limited doses. Its index of safety is relatively narrow. Therefore, an overdose of acetaminophen can lead to severe liver damage, which can result in acute liver failure subsequently. The clinical outcome of acetaminophen-induced acute liver failure ranges from full improvement and recovery to the need for liver transplantation or even death. Objective: The study aimed at reviewing the literature that has discussed different aspects of acetaminophen overdose-induced acute liver failure. Methods: PubMed database was used for articles selection and the following keywords were used in the MeSH: acetaminophen-induced acute liver failure, and acetaminophen-induced hepatotoxicity. A total of 35 papers were reviewed and included in the review. Conclusion: Acetaminophen overdose may and may not progress eventually to acute liver failure. Other than the dose, there are several risk factors that can affect the outcomes. The pairing of alcohol and acetaminophen is an issue that needs to spot the light on it.
    [Show full text]
  • Hepatoprotective Effect of Cimetidine and Ciprofloxacin on Paracetamol
    جملة البحوث اﻷكادميية العدد اخلامس يناير 6102 Hepatoprotective effect of cimetidine and ciprofloxacin on paracetamol-induced hepatotoxicity in male albino rats Nairuz Aboubaker Elsherif Department of Pharmacology, Faculty of Medicine, Benghazi University, Benghazi-Libya Abstract Paracetamol induced hepatotoxicity results from hepatic enzymatic oxidation of paracetamol to a toxic, electrophilic intermediate. Cimetidine and ciprofloxacin has been shown to inhibit the hepatic oxidation of a number of drugs.The present study was designed to investigate the hepatoprotective effect of cimetidine and ciprofloxacin against paracetamol induced hepatotoxicity in male albino rats. The hepatotoxicity was induced by the intraperitoneal(i.p) administration of paracetamol at a dose of 500 mg/kg in male albino rats. Biochemical analysis of plasma levels of ALT, AST, ALP, LDH and bilirubin were determined as measures of liver function. Our results showed that levels of liver enzymes ALT, AST, ALP, LDH and bilirubin level were significantly enhanced by administration of paracetamol indicating a considerable hepatocellular injury. However, the co-treatment with 150 mg/kg cimetidine i.p 2 hours prior to paracetamol injection revealed a significant attenuation of serum ALT, AST, ALP, LDH and bilirubin levels. 366 جملة البحوث اﻷكادميية العدد اخلامس يناير 6102 On the other hand, the co-treatment with 25 mg/kg ciprofloxacin i.p 2 hours before paracetamol treatment didn't show any protective effect on liver function. The present results clearly demonstrate the marked protective effect of cimetidine against paracetamol induced hepatotoxicity in rats, effect which could have been mediated via its inhibition of the CYP450 system responsible for the metabolism of paracetamol. Therefore, the production of the toxic metabolite (NAPQI) will be decreased.
    [Show full text]
  • Selected Topics: Toxicology
    The Journal of Emergency Medicine, Vol. 23, No. 3, pp. 253–256, 2002 Copyright © 2002 Elsevier Science Inc. Printed in the USA. All rights reserved 0736-4679/02 $–see front matter PII S0736-4679(02)00526-7 Selected Topics: Toxicology CHRONIC ACETAMINOPHEN TOXICITY: A CASE REPORT AND REVIEW OF THE LITERATURE Joshua E. Lane, MD,* Martin G. Belson, MD,† D. Kaine Brown, BS,* and Allison Scheetz, MD* *Department of Internal Medicine, Mercer University School of Medicine, Macon, Georgia and †Georgia Poison Center, Emory University School of Medicine, Atlanta, Georgia Reprint Address: Allison Scheetz, MD, Department of Internal Medicine, Mercer University School of Medicine, The Medical Center of Central Georgia, 777 Hemlock Street, Macon, GA 31208 e Abstract—Acetaminophen is one of the most frequently Hepatotoxicity resulting from chronic APAP thera- used medications in the United States. While usual dosing of peutic misadventures in adults has been previously re- acetaminophen is considered harmless, both acute and ported. The overwhelming majority of these cases occur chronic overdoses can be fatal. The majority of reported with chronic ethanol use or chronic use of P450-inducing cases of chronic acetaminophen toxicity in adults occur in medications (1-7). Additionally, an association between chronic alcohol abusers, patients taking P450-inducing chronic APAP use with short-term fasting and hepatotox- medications, or following massive dosing. We describe a case of toxic hepatitis free of the aforementioned risk fac- icity has been described (8,9). We present a patient who tors associated with chronic ingestion of moderately exces- developed significant hepatotoxicity from excessive chronic sive doses of acetaminophen.
    [Show full text]
  • TOXICOLOGY PARACETAMOL POISONING Pharmacokinetics and Mechanism of Toxicity Peak Serum Concentration: 4 Hours
    TOXICOLOGY PARACETAMOL POISONING Pharmacokinetics and Mechanism of Toxicity Peak serum concentration: 4 hours. Half life: 2-4 hours but longer in overdose. 90% conjugated with sulphate or glucuronide and excreted in urine. 2% excreted unchanged in urine. The remainder is metabolised to NAPQI by cytochrome P450 enzymes. N-acetyl-p-benzoquinoneimine (NAPQI) is a metabolite of paracetamol which irreversibly binds to cysteine groups on hepatic molecules and causes hepatocellular centrilobular necrosis through oxidative injury. Normally NAPQI is quickly bound to hepatic glutathione to form non-toxic compounds which are then excreted in the urine. In overdose the sulphation and glucuronidation pathways become saturated and more paracetamol is metabolised by the cytochrome P450 enzymes. This produces more NAPQI and glutathione becomes depleted. Unbound NAPQI then causes acute hepatic injury. Clinical Features Clinical Stage I (0-24 Stage II (1-3 days) Stage III (3-4 Stage IV (4 Features hours) days) days - 6 weeks) Symptoms N&V, lethargy or RUQ pain Confusion Recovery (4-7 asymptomatic days usually) Signs Hepatomegaly and Jaundice, RUQ tenderness encephalopathy LFTs Normal/abnormal Abnormal (50% by Bilirubin , AST Recovery over (ALT rises first) 24 hours, 100% by and ALT weeks 36 hours) elevated +++ Other Hypoglycaemia, Histologic lactic acidosis, recovery over coagulopathy, months. AKI, death AKI is caused by either acute tubular necrosis or hepatorenal syndrome. The risk of AKI increases with the severity of poisoning. N-acetylcysteine has not been shown to treat AKI. CAP 27 HAP 25 Stephen Foley 19/12/2016 Toxic Doses <75mg/kg over 24 hours – serious toxicity unlikely. 75-150mg/kg over 24 hours – toxicity uncommon but possible.
    [Show full text]
  • Biotransformer: a Comprehensive Computational Tool for Small Molecule Metabolism Prediction and Metabolite Identification Y
    BioTransformer: a comprehensive computational tool for small molecule metabolism prediction and metabolite identification Y. Djoumbou-Feunang, Jarlei Fiamoncini, A. Gil-De-La-Fuente, R. Greiner, Claudine Manach, D. S. Wishart To cite this version: Y. Djoumbou-Feunang, Jarlei Fiamoncini, A. Gil-De-La-Fuente, R. Greiner, Claudine Manach, et al.. BioTransformer: a comprehensive computational tool for small molecule metabolism prediction and metabolite identification. Journal of Cheminformatics, Chemistry Central Ltd. and BioMed Central, 2019, 11, 10.1186/s13321-018-0324-5. hal-01997281 HAL Id: hal-01997281 https://hal.archives-ouvertes.fr/hal-01997281 Submitted on 28 Jan 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution| 4.0 International License Djoumbou‑Feunang et al. J Cheminform (2019) 11:2 https://doi.org/10.1186/s13321-018-0324-5 Journal of Cheminformatics SOFTWARE Open Access BioTransformer: a comprehensive computational tool for small molecule metabolism prediction and metabolite identifcation Yannick Djoumbou‑Feunang1, Jarlei Fiamoncini2,3, Alberto Gil‑de‑la‑Fuente4, Russell Greiner5,6, Claudine Manach2 and David S. Wishart1,5* Abstract Background: A number of computational tools for metabolism prediction have been developed over the last 20 years to predict the structures of small molecules undergoing biological transformation or environmental deg‑ radation.
    [Show full text]