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Drug-Induced Liver Injury

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Presentation on theme: "Drug-Induced Liver Injury"— Presentation transcript:

1 Drug-Induced Liver Injury
Soheil Altafi MD 1/27/15

2 DILI- Table of Contents
Introduction Epidemiology Liver - Drug Metabolism Factors influencing Drug Metabolism Mechanisms of Drug-induced Hepatotoxicity Clinical Presentation Drugs that cause DILI Diagnosis Treatments

3 Introduction Caused by many common drugs
Antibiotics OTC medications Herbs Supplements 0.1 to 3% of hospital admissions1 ~600 liver transplantations per year in US 10% fatality seen in cases with severe ALT elevation and jaundice2 Caused by many common drugs prescribed or purchased without regulation Antibiotics-Augmentin, Bactrim, clarithromycin, Cipro, Levaquin, Moxi Anti-TB meds- isoniazid, pyrazinamide> rifampin or ethambutol OTC- ie Tylenol (acetaminophen) Herbs- ie St John’s Wart Supplement- weight loss, muscle building, niacin Dig Dis Sci 2007;52: Kaplowitz N. Nat Rev Drug Discov 2005;4:

4 Epidemiology Annual incidence between 10 and 15 per 10,000 to 100,000 people 30% of cases of acute hepatitis 10% of consultation by hepatologists Most common cause of acute liver failure in the US MCC of acute liver failure- acetaminophen being #1 drug to cause it

5 Liver - Drug Metabolism
Biotransformation Phase 1- oxidation 60 genes code for CYP (family- ie CYP2, subfamily- ie CYP2E1) Hepatic metabolism of exogenous drugs- CYP1, 2, 3, and lesser extent 4 CYP3A4- 60% of all hepatic cytochromes, affecting 50% of commonly used drugs Enzyme activity dependent on several exogenous factors State First- The liver is responsible for the selective uptake, concentration, metabolism, and excretion of the majority of drugs. While some drugs can cause hepatotoxicity prior to biotransformation, it is usually their metabolites that lead to DILI. Biotransformation- group processes by which a drug is metabolized into a more water-soluble form for purpose of excretion; in some cases the excreted metabolite may itself cause injury; while in other cases certain factors can lead to the concentration of metabolites, causing liver injury. Phase 1- transform lipophilic (water-insoluble) molecules into more polar, hydrophilic molecules via oxidation, reduction, or hydrolysis. These are membrane bound hemoproteins composed of an apoprotein and heme group (the oxidizing center). CYP- cytochromie P450 superfamily of mixed function oxidases, and are organized into families and subfamilies. Majority that metabolize drugs are found on the cytoplasmic side of the endoplasmic reticulum membrane. Factors that alter the activity of this group of enzymes have the potential to increase the toxicity of a compound. In some cases, alternate detoxification routes may become overloaded, leading to the development of hepatotoxicity.

6 Liver - Drug Metabolism
Biotransformation Phase 2- conjugation (UDP)-glucuronyl transferases (UGT1, & UGT2) Sulfotransferases Glutathione S-transferases Decreases pharmacologic activity Enhances clearance Phase 2 reactions affect the metabolites of phase 1 rxns in order to make them more hydrophilic for excretion. -These reactions conjugate the drug or metabolite byproducts to highly polar ligands such as glucoronate, sulfate, acetate, glycine, glutathione, or a methyl group. In general, drug conjugates are nontoxic, and phase 2 rxns are considered to be detoxification reactions, however polymorphisms of some of the enzymes may also lead to either decreased or increased activity.

7 Liver - Drug Metabolism
Biotransformation Phase 3 – transport ABC superfamily MDR1/ABCB1 MRP2/ABCC2 MDR3/ABCB4 BSEP/ABCB11 Altered activity of these transporters can lead to hepatotoxicity Phase 3 rxns lead to the transport of drugs/metabolites across the canalicular membrane and into bile. ABC- adenosine triphosphate (ATP)-binding cassette MDR- multidrug resistant P-glycoprotein BSEP- bile salt export protein

8 Factors influencing Drug Metabolism
Pharmacogenetics Polymorphisms of phase 1, 2, 3 enzymes Ie CYP2C9/2C19- warfarin, omeprazole, tolbutamide/mephenytoin Ie glutathione S-transferase- acetaminophen HLA- flucloxacillin, augmentin Nutrition Ie CYP2E1 Fasting/malnutrition Obesity Grapefruit Genetics- polymorphisms in this setting explains the four-fold or greater differences in rates of metabolism among healthy individuals. Genetic alterations may contribute to diminished metabolism, lack of metabolism, or excessive metabolism of a drug. -polymorphisms of CYP2C9- affects the metabolism of S-warfarin, omeprazole, tolbutamide -polymorphism of CYP2C19- affects the metabolism of S-mephenytoin -polymorphism of glutathione s-transferase can affect metabolism of acetaminophen -HLA (human leukocyte antigen)- association between certain HLA haplotypes and the development of DILI from fluclox-, augmentin Nutrition- A person’s nutritional status influences the expression of certain CYPs, both in health and with underlying liver disease. Expression of CYP2E1 is increased by obesity, high fat intake, and fasting -Fasting/malnutrition- may increase risk of DILI from acetaminophen; this is thought to be due to its affect on detoxifying cofactors such as glutathione -obesity- methotrexate, halothane -grapefruit juice- inhibits CYP3A, primarily acting on intestinal form of the enzyme; affecting levels of absorption of several drugs including immunosuppressive meds- cyclosporine and tacrolimus

9 Factors influencing Drug Metabolism
Multi-drug effect Age and sex Dose A drug may either inhibit or enhance (inducer) another drugs metabolism. Competitive inhibition of CYP can lead to clinically important drug interactions when there are no alternative pathway for the metabolism of a toxic drug or its metabolite. -Competition for phase 2 reactions such as glucuronidation and sulfation, for example, by phenytoin, may lower the dose threshold for acetaminophen-induced hepatotoxicity. -Phase 3 transporters have also been reported to be inhibited (eg, atorvastatin, carvedilol, clarithromycin, and sertraline) and induced (eg, amiodarone, diltiazem, erythromycin, and St John’s Wart); significantly altering the secretion activity of this group. During adult life, the expression of some CYPs declines by up to 10% with advancing age. Expression of CYP 3A4 and 2E1 seem to be different among men and women, which may explain the enhanced metabolism of certain drugs, however it’s still unclear whether this increases the risk of hepatic drug rxns. Severe DILI rarely occurs from drugs taken at doses less than 10mg; drugs administered at >/= 50mg are more likely to cause DILI.

10 Factors influencing Drug Metabolism
Disease-related changes- expression of CYP DM Hypothyroidism Underlying liver disease Decreased P450 Decreased hepatic clearance Diseases that alter the expression of CYPs include DM (increased CYP2E1), and hypothyroid (decreased CYP3A4) Cirrhosis is associated with decreased levels of total cytochrome P450 and also reduced hepatic perfusion; results in decreased clearance of such as propranolol, which is usually metabolized rapidly by the liver.

11 Mechanism of DILI Proposed mechanisms
Intrinsic injury (direct or indirect injury to hepatocyte) Drug transporter/metabolizing enzyme modulation Mitochondrial toxicity Bile Salt Export Pump (BSEP) inhibition Modulation of immune reactions (idiosyncratic injury) Histone acetylation Intrinsic injury- direct damage by covalently binding to cellular macromolecules (ie Tylenol, chloroform, carbon tetrachloride, phosphorus) Drug transporters such as BSEP or transporters on the sinusoidal membrane; Drug metabolizing enzymes such as CYP and phase 2 enzymes (ie glucuronidation or sulfation) may be inhibited or induced, essentially increasing the concentration of reactive metabolites within the hepatocyte. Mitochondrial toxicitity- which would essentially deplete the ATP stores, leading to cell death. BSEP- will discuss further in the presentation Histone acetylation- inhibiting cell regeneration by blocking DNA transcription

12 Mechanisms DILI can result from reactive drug metabolites; their concentration depends on toxification and detoxification enzymes.

13 Mechanisms Most toxic drugs have a direct effect on the hepatocyte, causing necrosis or apoptosis. Mitochondrial toxicity essentially blocks the cells ability to produce ATP, leading to cell death. The toxic drug or metabolite may also directly trigger cell death through the TNF/Fas system. A drug/metabolite maybe recognized by a cytotoxic T-cell to release cytokines, triggering immune-mediated cell death. This is where HLA subtyping plays a role. Histone acetylation by other drugs/metabolites will essentially inhibit the cells ability to regenerate. Some drugs predominately damage the bile ducts, or affect the export proteins (BSEP), leading to cholestasis. While other drugs may cause a mixed injury pattern.

14 Mechanisms BSEP- Inhibition of bile acid transporters, such as BSEP (bile acid export pump), results in the accumulation of bile acids within the hepatocyte, causing cell injury through their detergent properties or direct toxic effect on mitochondria.

15 Clinical Presentation
Hepatocelluar (cytotoxic) injury Cholestatic injury Mixed injury Mechanism of hepatotoxicity Predictable Idiosyncratic Histologic findings (liver biopsy usually not necessary) Hepatitis Cholestasis Steatosis Type of injury is reflected by the pattern of liver test abnormalities. Hepatocellular injury- 1) aminotransferases are elevated much more than ALP; 2) serum bili may be elevated; 3) test of synthetic function abnml Cholestatic injury- 1) ALP elevated more so than aminotransferases; 2&3 same as above Acute DILI- LFTs abnml for less than 3 months; Chronic DILI- abnml for more than 3 months

16 Clinical Presentation
Predictable- intrinsic hepatotoxins Predictably cause dose-dependent hepatocellular necrosis Latent period- brief (hours to a few days) Fairly consistent from person to person and among animal models Serum aminotransferases 8 to 500 times normal; ALP less elevated Often removed from clinical use Some still in use due to known dose-related toxicity Hepatotoxic in large doses (ie acetaminophen, iron sulfate) Known dose-effect (ie ethanol, IV tetracycline, L-asparaginase)

17 Clinical Presentation
Idiosyncratic Unpredictable Species-specific, often cannot be reproduced in animal models Latent period- variable, generally 1 to 3 months Doses >50mg/day more likely to cause DILI compared to dosing <10mg

18 Clinical Presentation
Hepatocellular ALT/ALP ratio >5 ~50% of DILI is hepatocellular AST>>ALT- think muscle injury or alcoholic hepatitis Neither above 400 Cholestatic ALP> 2x ULN ALT/ALP ratio < 2 Mixed 5> ALT/ALP ratio > 2 Hy’s law- serum bilirubin >2x ULN, aminotransferases >3x ULN Associated with worse prognosis Mortality as high as 14 percent Hy’s Law – developed by Hyman Zimmerman

19 * Add slide on Methotrexate monitoring- primo gastro

20 Clinical Presentation
Acute DILI Mild asymptomatic liver test abnormalities Cholestasis with pruritis Acute illness with jaundice- resembles viral hepatitis Acute liver failure Chronic DILI- may resemble AIH PBC Sclerosing cholangitis Alcoholic liver disease Asymptomatic abnml liver chemistries- 1/100 to 1/100,000 ; most resolve with drug cessation Acute illness with jaundice- 10 to 14% mortality due to liver failure Will review Acute Liver Failure further in the presentation *Add slides about DILI-like AIH

21 Clinical Presentation
Symptoms Acute DILI Malaise Low-grade fever Anorexia Nausea and Vomiting RUQ pain Jaundice Acholic stools Dark uine Chronic Dili may present with signs of cirrhosis or decompensation Jaundice Palmer erythema Ascites HE

22 Acetaminophen Hepatotoxicity
Normally metabolized by glucuronidation and sulfation N-hydroxylation (CYP2E1)  N-acetyl-p-benzoquinone (NAPQI) NAPQI scavenged by glutathione Overdose usually >7-10gm (in nonalcoholic patients) Glutathione depleted increased NAPQIhepatotoxicity CYP2E1 induced by fasting, alcohol, Rx (ie INH), Treatment Ipecac- if time of ingestion <4hrs N-acetylcysteine (NAC)- increases level of glutathione

23 Drugs that cause DILI Isoniazid (INH) – 300mg qD
Mechanisms Reactive metabolites Immunoallergic injury: HLA DQB1*0201 Mitochondrial injury Inhibiting histone deacetylase Presents insidiously 4-6 months after Rifampin increases likelihood of INH tox INH can increase acetaminophen tox Hx of liver disease- serial monitoring (alternate drug if level >100) Amoxicillin:clavulanate mg qD Immunoallergic injury: Class 1 & 2 HLA DQB1*0602, *1501 Cholestatic hepatitis within weeks of first dose Valproate (>600mg qD) -Mitochondrial injury -Inhibiting histone deacetylase -Low carnitine levels- increases risk of liver injury

24 Drugs that cause DILI Nitrofurantoin
Liver injury usually seen in women taking for >6 months Labs- high transaminases; HLA-B8 and ANA are usually positive Steroids (anabolic, OCP, tamoxifen, glucocorticoids) Cholestatic injury Canalicular injury Anesthetic Agents (ie Halothane) Risk increases with more exposure and present within 2 weeks Labs- eosinophilia, AST/ALT IU/L Mechanism- reactive metabolites (trifluoroacetyl), and autoanitgens Poor prognosis- age>40, obesity, HE, elevated INR (mortality 80% without OLT)

25 Herbal & Supplements 9-14% of cases of DILI in Western countries
Longer exposure before DILI 42% in US use some form of alternative therapy 69% do not disclose supplement use to health care providers 52% use herbal/sup concurrently with prescription meds Common- Herbalife, Hydroxycut, Chinese herbal, LipoKinetix, Androstenedione, Black cohosh, Green tea extract, Mistletoe, Licorice




29 Diagnosis Obtaining a thorough history
Performing blood test to look for other causes on hepatic injur Cholestasis- imaging to rule out biliary obstruction Review of drugs exposed preceding the onset of liver injury Underlying liver disease is excluded- rule out other causes Stopping drug believed to cause injury leads to improvement Rechallenge- rapid and severe recurrence; not advised

30 Diagnosis Drug exposure
Stop drugs that are commonly known to cause DILI Always ask about any OTC, herbal and/or supplements taken If possible review a patient’s pharmacy records Check drugs on Case presentations Drug-specific liver injury characteristics Direct link to references and other online recources New cases of DILI welcome

31 Diagnosis Roussel Uclaf Causality Assessment Method (RUCAM)
A number of scales have been developed that attempt to categorize causality of drug toxicity -Roussel Uclaf Causality Assessment Method (RUCAM) -Maria & Victorino clinical scale -The Drug-Induced Liver Injury Network (DILIN) developed the DILIN Causality Scoring System- which relies on expert opinion These scales do not address all risk factors in all patients; and none are used routinely in clinical practice.

32 Diagnosis Drug-induced acute liver failure
Most frequent cause of liver failure requiring evaluation for transplantation 11th Annual FDA/PhRMA/AASLD Hepatotoxicity Conference Acute Liver Failure Study Group ~1700 cases Acetaminophen-induced 46% (n=787) Other drug-induced liver failure 12% (n=202) Acetaminophen-induced- half unintentional narc/aceta overdose Coagulopathy (INR>1.5) Encephalopathy- day/night confusion, disorientation, sleepiness Acute liver failure is rare- 1-5 per million per year -75% fatality with non-acetaminophen DIL Failure -32% fatality in acetaminophen-ALF

33 Treatment of DILI Discontinue suspected drug- most cases, liver injury should spontaneously resolve N-Acetylcysteine for acetaminophen liver injury Liver transplantation Limited use or experimental IV carnitine for valproate liver injury Ursodeoxycholic acid for cholestasis Corticosteroids for hypersensitivity cases Plasmapheresis

34 The End

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