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