Download HEPATOTOXICITY

DRUG INDUCED
HEPATOTOXICITY
Ackerman Zvi M.D.
Hadassah-Hebrew University Medical
Center
Inputs and Outputs
First pass ???
Hepatic recycle ???
Heart
Intestines
Hepatic
Artery
Hepatic
Vein
Portal
Vein
LIVER
Bile
Duct
PREDICTIVE PARAMETERS OF
DRUG-INDUCED LIVER INJURY
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There are relatively few ways by which acute and
chronic liver diseases become clinically manifest..
Signs and symptoms of drug-induced liver disease are
generally nonspecific and reflect more the extent of the
liver injury than the cause.
Slight elevations of aminotransferase or alkaline
phosphatase levels do not of themselves cause
symptoms and may be present as only as an
abnormality of one or more biochemical test detected
during a random predetermined evaluation schedule.
Most instances of drug-induced aminotransferase
elevations are transient and nonprogressive.
Spectrum of DILI
ALF
(Death, Txp)
0.0001 - 0.01%
Symptomatic
disease
0.01 - 1.0%
Mild liver injury
(ALT < 3X ULN)
0.1 - 10%
Tip of the Iceberg
Death or Tx
Acute Liver Failure
Serious DILI – Threatening
Detectable DILI – but Not Serious
Patient Adaptation to New Agent Exposure
Patients/People Tolerate Exposure Without Effects
SPECTRUM OF HEPATOTOXICITY
INDUCED BY DRUGS-1
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minimal, nonspecific alterations in biochemical
tests of no clinical consequence
to acute hepatitis
chronic hepatitis
acute liver failure
prolonged cholestatic disease
cirrhosis
hepatic tumors.
Drug-Induced Liver Injury (DILI)
“adaptors”
Time Course of Liver Tests
"adaptor" - M63 - transaminase rises only
100.0
ALTx
ASTx
stop drug
ALPx
10.0
TBLx
1.0
0.1
-60
0
60
120
180
240
300
360
420
480
540
600
660
720
780
840
900
960
1020
1080
1140
1200
1260
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1440
1500
1560
1620
1680
1740
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1860
1920
1980
2040
2100
Test Values, xULN
start drug
Days Since Exposed to Drug
SPECTRUM OF HEPATOTOXICITY
INDUCED BY DRUGS-1
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minimal, nonspecific alterations in biochemical
tests of no clinical consequence
to acute hepatitis
chronic hepatitis
acute liver failure
prolonged cholestatic disease
cirrhosis
hepatic tumors.
death
jaundice
enceph
Days on drug
Slide from Paul Watkins
Sulphasalazine Hepatotoxicity
CAH from Methyldopa
SPECTRUM OF
HEPATOTOXICITY INDUCED
BY DRUGS-2
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Furthermore, some drugs have been shown to
cause :
fatty liver (simulating alcohol-induced liver
disease)
granulomas (simulating sarcoidosis)
acquired phospholipidosis
predispose to development of the Budd-Chiari
syndrome or veno-occlusive disease.
Amiodarone induce NASH
Post BMT veno- occlusive disease
Normal Liver
Mechanism of liver injury-1

Disruption of itra-cellular calcium homeostasis
leads to disassembly of actin fibrils at the
surface of the hepatocyte, resulting in blebbing
of cell membrane, rupture, and cell lysis
Mechanism of liver injury-1
Mechanism of liver injury-2
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
In cholestatic diseases, disruption of actin
filament may occur next to the canaliculus, the
specialized portion of the cell responsible for
bile excretion.
Loss of villous process and the interruption of
transport pumps such as multidrug-resistanceassociated protein 3(MRP3) prevent the
excretion of bilirubin and other organic
compounds
Mechanism of liver injury-2a
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Drugs that affect transport proteins at the
canalicular membrane can interrupt bile flow.
Certain drugs, for example, bind to or disable
the bile salt export protein. This process causes
cholestasis; however, little cell injury occurs.
Genetic defects in transporters, as in the
multidrug-resistance–associated protein 3, in
combination with hormones may promote
cholestasis during pregnancy or during treatment
with estrogen-containing medications.
Mechanism of liver injury-2
Cholestasis from estrogens
Mechanism of liver injury-2b
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In mixed forms of hepatic injury, the combined
failure of canalicular pumps and other
intracellular processes allows toxic bile acids to
accumulate, causing secondary injury to
hepatocytes .
If cells of the bile ducts are injured, a likely
outcome is protracted or permanent cholestasis,
a disorder that has been termed the "vanishing
bile duct syndrome."
Mechanism of liver injury-3a
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Drugs are relatively small molecules and, therefore,
are unlikely to evoke an immune response.
However, biotransformation involving high-energy
reactions can result in the formation of adducts —
that is, drugs covalently bound to enzymes.
Mechanism of liver injury-3b
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Adducts that are large enough to serve as
immune targets may migrate to the surface of
the hepatocyte, where they can induce the
formation of antibodies (antibody-mediated
cytotoxicity) or induce direct cytolytic T-cell
responses .
The secondary cytokine response thus evoked
may cause inflammation and additional
neutrophil-mediated hepatotoxicity
Mechanism of liver injury-3
Mechanism of liver injury-3 con
Mechanism of liver injury-3c
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For a growing number of drugs, there is evidence that
genetic polymorphism in metabolic pathways are
important in determining which individuals are likely to
have an adverse reaction.
Immunologic reactions of the immuno-allergic type
appear to play less important (or at best augmenting)
roles in the production of most drug-induced injuries.
Haptens formed by a drug product and a cellular
constituent may provoke formation of antibodies to
the neo-antigen and add to injury.
Reactions to several drugs, including halothane,
diphenylhydantoin, and sulindac, occur in settings
suggesting
Mechanism of liver injury-4
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Programmed cell death (apoptosis) can occur in
concert with immune-mediated injury,
destroying hepatocytes by way of the tumor
necrosis factor (TNF) and the Fas pathways,
with cell shrinkage and fragmentation of nuclear
chromatin
Proapoptotic receptor enzymes, if activated by
drugs, will compete with protective so-called
survival pathways within the cell, and this
dynamic interaction may shift the balance either
in favor of or against further cell damage.
Mechanism of liver injury-4
Mechanism of liver injury-5a
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Certain drugs inhibit mitochondrial function by
a dual effect on both -oxidation (affecting
energy production by inhibition of the synthesis
of nicotinamide adenine dinucleotide and flavin
adenine dinucleotide, resulting in decreased ATP
production) and the respiratory-chain enzymes.
Free fatty acids cannot be metabolized, and the
lack of aerobic respiration results in the
accumulation of lactate and reactive oxygen
species.
Mechanism of liver injury-5 b
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. The presence of reactive oxygen species may
further disrupt mitochondrial DNA.
The presence of reactive oxygen species may
further disrupt mitochondrial DNA.
This pattern of injury is characteristic of a
variety of agents, including nucleoside reversetranscriptase inhibitors, which bind directly to
mitochondrial DNA, as well as valproic acid,
tetracycline, and aspirin.
Mechanism of liver injury-6
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Other cells within the liver may be the target of drug
injury or serve as modulators of an incipient reaction.
For example, Kupffer's cells activate cytokines that
may amplify injury, and fat-storage cells (stellate cells)
or macrophages may augment injury, produce fibrosis,
or form granulomas.
Chemotherapeutic agents can injure sinusoidal
endothelial cells, a process that can lead to venoocclusive disease.
Therapeutic hormone administration may induce
hepatocyte dedifferentiation, resulting in benign
adenomas and, rarely, carcinomas.
Clearly, multiple cellular pathways to liver injury are
possible.
Sinusoidal Damage
Methotrexate induced fibrosis
Vitamin A Toxicity
When to suspect DILI-1
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There are few clinical or laboratory manifestations
which specifically suggest that a liver injury is the result
of a therapeutic drug. The most important clue is often
the temporal relationship between initiation of a drug
(or drugs) and the appearance of the injury, and of
equal importance is the resolution of an abnormality
following withdrawal (deceleration).
In many (likely most) instances, a slight elevation of a
serum aminotransferase is of no clinical importance
and may well resolve through poorly understood
adaptive mechanisms that develop with continued drug
use.
Drug-Induced Liver Injury (DILI)
Most people exposed to a new drug show no injury;
“tolerators”
Some people show transient injury, but adapt;
“adaptors”
A few fail to adapt and show serious toxicity !
“susceptibles”
Drug-Induced Liver Injury (DILI)
“tolerators”
Time Course of Liver Tests
"tolerator" - M47 - Gilbert's syndrome
100.0
ALTx
ASTx
stop drug
ALPx
10.0
TBLx
1.0
0.1
-60
0
60
120
180
240
300
360
420
480
540
600
660
720
780
840
900
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1020
1080
1140
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1500
1560
1620
1680
1740
1800
1860
1920
1980
2040
2100
Test Values, (xULN)
start drug
Days Since Exposed to Drug
When to suspect DILI-2
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The combination of elevated aminotransferase
(at least >3 × ULN) and clinically evident
jaundice (>3 mg/dL) identifies patients at
heightened risk of developing severe injury.
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Definition of DILI for inclusion Criteria
Serum ALT or AST >5 x ULN or A P’ase >2 x
ULN confirmed on at least 2 consecutive blood
draws.
If baseline (BL) ALT, AST or A P’ase are known
and elevated, then ALT or AST >5 x BL or A P’ase
>2 x BL on at least 2 consecutive blood draws.
or Any elevation of serum ALT, A P’ase, or
AST, associated with (a) increased serum total
bilirubin [ ≥ 2.5 mg/dL], in absence of prior
diagnosis of liver disease, Gilbert’s syndrome, or
evidence of hemolysis.
Acute DILI
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Hepatocellular: R > 5 and ALT > 2x ULN or
baseline
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Cholestatic: R < 2 and Alk > ULN
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Mixed: 2< R < 5
R= (ALT/ULN)/ (Alk / ULN)
(J Hepatol 1990; 11: 272)
Hy
Zimmerman
1917-1999
“Hy’s Law”
...for drug-induced hepatotoxicity
 If
both hepatocellular injury and
jaundice occur, look out for at
least 10% mortality!
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i.e., when both transaminase and bilirubin
elevations occur together.
Robert Temple, FDA, 1999
Prognosis in Acute Liver Failure
Etiology an important outcome determinant
Good prognosis:
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Acetaminophen
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Hepatitis A
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Shock
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Bad prognosis:
Drugs
Indeterminate
Hepatitis B
Wilson Disease
… not DILI
Time Course of Liver Tests
male 72, placebo
altx
100.0
start drug
astx
stop drug
bilx
10.0
2xULN
1.0
subacute hepatitis B
Study Day
600
570
540
510
480
450
420
390
360
330
300
270
240
210
180
150
120
90
60
30
0
-30
0.1
-60
Test Values, xULN
alkx
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A significant number of drugs has been proven,
or at least suggested, to cause hepatotoxicity.
It must be recognized that a drug is a chemical
or biologic agent that has been found to cause a
favorable effect on a symptom or disease
process, has been tested for safety (relative), has
been given a name, and then if approved, is
widely available.
Usually, the propensity to cause liver injury is
identified during preapproval evaluations,
especially those in large pivotal Phase 3 trials.
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Attribution of liver injury to a specific drug in a
patient may be difficult, and the difficulties are
compounded if the patient has underlying acute
or chronic liver disease such as chronic hepatitis
C, chronic hepatitis B, nonalcoholic fatty liver
disease, or alcohol-induced liver disease.
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Much attention has been given to the
identification of factors that identify individuals
who are at increased risk of developing an
adverse hepatic reaction from a drug.
There are concerns not only about the drug
itself, but also about the effects of drug-drug
and drug-disease interactions.
In general, it appears that patients with acute or
chronic liver diseases are not more likely to
develop a hepatotoxic reaction of the
idiosyncratic type.
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However, especially in patients who have
advanced liver disease, any adverse hepatic
reaction that occurs is more likely to lead to
clinical evidence of liver injury, in part related to
decreased liver mass and decreased abilities to
respond to the injury and appropriately
regenerate hepatocytes.
Drug Signature
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Most drugs have a “signature” of hepatotoxicity
regarding time of onset, frequency, and type of
hepatotoxicity that may be encountered.
When to suspect DILI-3
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There may be few clinical signs suggesting liver injury,
even in a patient who has biochemical and histologic
evidence of considerable damage.
Early symptoms associated with drug-induced liver
injury are usually nonspecific and include loss of
appetite, lassitude, and occasionally a dull discomfort in
the right upper quadrant of the abdomen.
With a few drugs, there is the presence of fever, rash,
or eosinophilia: the hallmarks of immuno-allergic
reactions. These reactions may (or may not) be
important in the pathogenesis of the liver injury.
When to suspect DILI-4
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Rechallenge with a suspected drug to establish a
diagnosis is seldom necessary and, if the initial
reaction was clinically apparent, may not be safe.
Even histologic evaluation of the liver only
allows recognition of what type and how much
injury is present, rather than clearly indicating
that the liver injury is from a specific drug.
Drug-Induced Liver Injury (DILI)
“susceptibles”
Time Course of Abnormalities
Patient xxx F44, "susceptible"
2.0 100xULN
start Drug
stop Drug
ALT
AST
1.5
GGT
1.0 10xULN
TBL
0.5
ULN
0.0
------------hospitalized-----------------
-0.5
Study Day
120
105
90
75
60
45
30
15
0
-1.0
-15
Log(10) of xULN
ALP
FACTORS THAT AFFECT
SUSCEPTIBILITY TO DILI-1
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Age, sex, and the concomitant use of other
medications are important factors to consider in
assessing an individual patient's susceptibility to
drug-induced liver disease, as is weight and a
history of previous reactions to drugs. .
For some drugs, there is a well-established
increase in the risk of adverse reactions with
age, especially for individuals who are older than
50 years
FACTORS THAT AFFECT
SUSCEPTIBILITY TO DILI-2
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Older patients (>50 years) are quite likely to
have some evidence of hepatic toxicity from
isoniazid (up to 2%).
Few reactions have been reported in patients
who are younger than 20 years.
There are a few agents, among them valproic
acid and erythromycin estolate, which
predominantly cause adverse hepatic reactions in
children
FACTORS THAT AFFECT
SUSCEPTIBILITY TO DILI-3
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Valproic acid-induced hepatotoxicity is also more
prevalent in patients who have inherited mitochondrial
disorders.
Duration of therapy before a reaction occurs is an
important part of the “signature.”
Phenytoin rarely causes significant hepatic toxicity after
6 weeks of therapy.
Liver injury from nitrofurantoin-induced hepatotoxicity
may appear after many months of therapy.
FACTORS THAT AFFECT
SUSCEPTIBILITY TO DILI-4
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For many drugs, females are at an increased risk
of developing an adverse hepatic reaction, far
exceeding that found in males.
Acute hepatitis: Differential Dx
Ultrasound/ CT
++
Viral
(A, B, C, CMV, EBV
HEV, HSV)
Autoimmune
(SPEP, ANA, SmAb)
NAFLD
Mass
(AFP, MRI)
Ischemia
(History, 2D-Echo)
Metabolic
(Iron, TIBC, ferritin,
ceruloplasmin, SPEP)
Drug
Observe/ biopsy
Biliary
(ERCP)
Liver Lobule
Liver Function
Example
Consequence
Glucose metabolism, protein
metabolism, storage of nutrients
Glucose storage as glycogen
Hypoglycemia, altered protein
synthesis, decreased vitamin A,
Cu, Fe
Filtration
Removal of polypeptides,
lipoproteins coming from GI track
Endotoxemia
Protein synthesis
Albumen
Transport proteins
Blood clotting factors
Hypoalbumenia, ascites,
decreased blood clotting
Removal of bile pigments
Bile acids
Jaundice
Lipid metabolism
Cholesterol
Increased levels
Xenobiotic removal and
metabolism
Drugs, toxins, metals
Protection, intoxication
Commonly Used Tests
“transaminases”: ALT
enzymes
AST
alkaline phosphatase
injury
hepatocellular
cholestatic
gamma-glutamyl transferase
bilirubin (total, “direct”)
substances
function
excretory
albumin
synthetic
prothrombin (INR)
synthetic
DILI Diagnosis
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Temporal relationship
Not dose related
 ? Clinical risk factors
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Biochemical injury pattern
“Signature” vs protean
 Prior reports/ cases
 Exclude other likely causes
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Improvement with discontinuation
Drug Induced Liver Injury
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Two types of hepatotoxicity are of interest:
 Dose-related-or exposure related.
 Idiosyncratic-rare, unpredictable.
Factors in Idiosyncrasy

genetic, bestowed at onception
gender
cytochromes,

enzymes, transport systems
acquired in life since conception
age,
activities, travels
infections, immunities, diseases
diet, obesity, dietary supplements
other drugs, chemical exposures
Especially Susceptible Patients
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adverse effect, often not dose-related
may not be duration-related
may not depend on prior disease
unexpected, unpredictable (up to now)
risk factors not well known
toxicity often uncommon or rare
who are they? how can they be
identified?
Intrinsic vs Idiosyncratic Toxicity
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“intrinsic”
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predictable
dose-related
similar in animals
high incidence
short interval
types
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directly destructive
indirect, metabolic
cholestatic
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“idiosyncratic”
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unpredictable
not dose-related
not seen in animals
low incidence, rare
variably longer interval
types
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hypersensitivity
metabolic
It may be DILI if it’s nothing
else
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Diagnosis of exclusion; no test FOR DILI
Must gather data to rule out other causes
Need to educate “docs” to do it better
Develop model for quantitative likelihood estimate
Prospective large safety studies needed:
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for true incidence
for risk factors and to design risk management plans
for ‘omic’ analyses (gen-, prote-, metabon-) specimens
for elucidation of mechanisms
Acetaminophen-induced hepatic
injury 1
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Acetaminophen-induced hepatic injury is the most
common form of drug-induced liver disease and more
particularly of acute liver failure in the United States,
accounting for nearly 50% of all cases.
Acetaminophen is likely the most widely used drug in
the western world and is found in a remarkable number
of prescribed and over-the-counter single and
combination products, including cold remedies and
medications for pain. with names that in no way
indicate acetaminophen is a component.
Acetaminophen-2
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In healthy individuals, there is apparently a considerable
therapeutic range between harmless and harmful doses
of acetaminophen. In therapeutic doses (<3 g/day), the
drug is usually quite safe and well tolerated.
Ingestion of excessive amounts of acetaminophen
(>10-15 g), often in suicidal attempts, predictably leads
to liver injury and occasionally death.
The issues lie in assessing the risk of patients receiving
acetaminophen of 3 to 10 g/day, and whether there are
settings in which liver injury is more likely to occur
when the patient has not taken a large amount of the
drug with a suicidal intent (so-called “therapeutic
misadventures”).
Normal
Acetaminophen
P450
5%
NAPQI
95%
(N-acetyl-p-benzoquinoneimine)
Sulfate
Glutathione
Glutathione
Conjugate
Glucuronide
Overdose
Acetaminophen
P450
5%
NAPQI
95%
(N-acetyl-p-benzoquinoneimine)
Sulfate
Saturated
Glucuronide
Covalent
Binding to
Macromolecules
Glutathione
Glutathione
Conjugate
Cell Death
(Zone 3)
Acetaminophen- 3
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Hepatic injury from acetaminophen is caused by the
effects of a highly reactive metabolic product, N-acetylbenzoquinone-imide (NAPQI).
Acetaminophen is predominantly metabolized by
conjugation reactions to form sulfate and glucuronide
metabolites, which are excreted in the urine.
A lesser amount of the drug is metabolized by
cytochrome P450 2E1 to form NAPQI, which is
rapidly bound to intracellular glutathione and excreted
in the urine as mercapturic acid.
Acetaminophen- 4
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When excessive amounts of acetaminophen are
ingested, the ability to conjugate is overwhelmed and
metabolism by cytochrome P450 2E1 becomes of
much greater importance.
In these situations, the capacity of glutathione to serve
as an effective hepatoprotectant may be overwhelmed,
and the hepatocyte becomes relatively defenseless
against attack by the reactive intermediates
Oxygenation Zones
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Zone 1 – 9% to 13%
Zone 2 – < zone 1
Zone 3 – 4% to 5%
Zone 3 has most of the
biotransformation enzymes
especially CYP2E1
Acetaminophen- 5
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Two important factors determine the likelihood
of production of hepatic injury by
acetaminophen: the amount of NAPQI
produced by P450 2E1 and the availability of
glutathione as a hepatoprotectant.
The intracellular concentration of NAPQI and
dose of acetaminophen ingested are clearly
associated. However, there is more to the story
than simply dosage.
Factors that affect the production of
cytochrome P450 2E1 and of glutathione are of
importance
Acetaminophen- 6
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With chronic ingestion of alcohol, doses of
acetaminophen near or even with the suggested
therapeutic range may lead to liver injury, promoted by
an
alcohol-induced decrease in intracellular
glutathione
and an increase (actual or relative to GSH) of
cytochrome P450 2E1.
The end result is overproduction of NAPQ1 relative
to the dispositional pathway of GSH leading to a
heightened likelihood of liver
Acetaminophen- 7
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There continues to be controversy regarding the risk of
acetaminophen use in patients who drink alcohol.
Many discussions have occurred at the U.S. Food and
Drug Administration regarding labeling and the need
for increased awareness of risks by the public.
There is general agreement that an overdose of
acetaminophen is more likely to cause liver injury in a
patient who is a chronic alcoholic.
The debate is the definition of overdose and the
amount of alcohol ingestion needed to predispose the
patient to injury
Acetaminophen

Toxic dose
150mg/kg in children less than 12
 Estimated at 7.5 g for adolescents and adults


4 stages in untreated patients
Stage I (0 - 24h) - nausea, vomitting, diaphoresis
 Stage II (24 - 48h) - clinical improvement, RUQ pain
 Stage III (72 - 96h) - peak liver function abnormalities,
GI symptoms may reappear
 Stage IV (4d to 2wks) - hepatic problems resolve, <1%
will develop fulminant hepatic necrosis requiring a liver
transplant

Acetaminophen

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Measure a plasma acetaminophen
level at >4h after ingestion
Antidote is N-acetylcysteine - most
effective within 8 hours of
ingestion
Give antidote if at risk for
hepatotoxicity
Activated charcoal should be
considered
Amoxicillin/Clavulanic Acid
Hepatotoxicity
Case Presentation
 68 yo female
 Referred for transplant evaluation
 Jaundice and failure to thrive
 3 month illness
 Laparotomy x 2, cholecystectomy
and multiple pancreatic head biopsies
 Biopsy profound cholestasis and bile duct injury
 Small nasal scar, solar keratosis surgery
 Dermatologists records
• No malignant
• Infected
• Augmentin for 14 days
Therapeutics: Prescribing
Information
Amoxicillin
•
•
•
Semisynthetic antibiotic
C16H19N3O5S.3H20
MW = 419.46
•
•
•
Potent β- lactamase inhibitor
C8H8KNO5
MW = 237.25
clavulanate potassium (salt)
Addition of
clavulanate prevents degradation of
amoxicillin by β- lactamases
Mechanism of Action
unclear
Idiosyncratic/immunologic
• Not dose dependent
• Prevalence not uniformly assoc with re-exposure
• Eosinophilia
• HLA association
Not seen with amoxicillin alone
Presumed due to clavulante
Cholestasis described with Timentim®
•
•
Ticarcillin + clavulante
Rarely observed with sulbactam, tazobactam;
i.e. other β lactamases
Therapeutics: Prescribing
Information
“Indicated for the treatment of
infections caused
by susceptible strains of the following designated
organisms”:
•
•
•
•
•
•
H. influenzae; M. catarrhalis; E. coli; S. aureus;
Klebsiella spp, Enterobacter spp
Lower respiratory tract infections (COPD)
Otitis media
Simusitis
Skin and skin structure infections
Urinary tract infections
Therapeutics: Prescribing
Information
Augmentin®
First introduced 1981
Generics introduced 2001-2002
Hepatotoxocity first reported 1988
Year 2000
• 18.9 M new prescriptions
• Fourth most commonly prescribed drug
US Frequency Hepatotoxicity
Assuming incidence between
• 1: 100,000 and
• 1:10,000
• ≈ 20 million new prescriptions annually
Number of
expected cases HTX
• ≈ 200-2,000 per year
• ≈ 122-1,220 adult cases
• ≈ 78-780 pediatric cases ??
Frequent Concomitant
Medications
 Pyrexia associated with bacterial Unclear, not well
documented
 infections
 Acetominophen probably common
 8/21 (38%) cases exposed to other HTX drugs
•
•
•
•
•
•
•
Acetominophen
NSAID’s
Trimethoprim
Flucloxacillin
Valproate
Carbamazepine
imipramine
 43% another potential or suspected agent
Clinical Presentation
 Signs and Symptoms are nonspecific
•
•
•
•
•
•
•
•
•
Nausea
Vomiting
Fatigue
Malaise
Abdominal pain
fevers
Itch
Jaundice
rash
•
Eosinophilia 23-30% patients
 Allergic phenomena:
Clinical Presentation
Timing
• Interval start Rx to jaundice
4-63 days (89 days)
• Cessation Rx to onset jaundice
1-48 days
• 80% developed jaundice after cessation Rx
Larrey D et al. Gut 1992;33:368-71
Hautekeete ML et al. Gasroenterology 1999:117;1181-86
Clinical Presentation
Laboratory tests
• Bilirubin
• ALT
• AST
• AP
• γGT
2-35 x ULN
2-33 X ULN
1.2-18 x ULN
1.7-13 x ULN
2.5-52 x ULN
Clinical Presentation
Pattern of
Laboratory tests
• Cholestatic
66-76%
• Mixed
14-23%
• Hepatocellular
10-11%
Clinical Presentation
Liver Biopsy
 Architecture normal
 Mixed, LM portal infiltrate
 Intralobular Bile ducts
 Nuclear irregularity
 Vacuolization
 LM infiltrate
 Proliferation
 Cholestasis lobules
 Variable degrees necrosis
 Mild cellular infiltrate
 Rarely
 granulomas; focal destructive cholangiopathy
Outcome of Hepatotoxicity
 Fatalities rare but reported
 Chronicity uncommon
 Jaundice can be prolonged
•
•
up to 19 weeks
1 case 2 years
•
•
•
PBC
Interstitial nephritis
Sialadenitis
 Cases associated with
 ? Underlying liver disease
 Pre-exisiting DILI
HLA Class II Association
 DRB1*1501-DRB5*0101-DQB1*0602
 35 cases, 300 donors
 57% vs 11.7% (p < 0.0002)
 haplotype more frequently assoc. with cholestatic/mixed
 22 cases, 134 controls
 70% vs. 20% (p < 0.00005; RR 6.43)
 More frequently homozygotes
 No clinical correlates
 ? Formation neo-antigen
and their recognition as foreign
Minimal Criteria for Causality
Amoxicillin/clavulanic acid
 Start and stop date
 Age, sex, demographics
 Drug exposure within 8 weeks
 Serologic tests
 Additional but not necessary
•
•
•
•
•
•
Prior exposure
Eosinophils
biopsy
Dosage
Imaging to exclude obstruction
Concomitant medications
“Definite” Case
Amoxicillin/clavulanic acid
Male
Age > 50-55 yo
Cholestatic pattern
Repeat exposure
Eosinophilia
Imaging negative
Onset after cessation of drug
Recovery within 6-8 weeks
All serologies negative
Isoniazid Hepatotoxicity -1




Isoniazid has been the mainstay therapeutic agent for
the treatment of tuberculosis for more than 50 years.
Combination therapies anchored by INH are generally
used to prevent the development of resistance to a
single therapeutic agent.
In the 1960s, INH was used as a single agent in patients
who were found to be at risk for developing
tuberculosis because of the findings of a positive
tuberculin skin test.
INH given alone often leads to elevations of
aminotransferase and occasionally to overt liver disease.
Isoniazid Hepatotoxicity -2

When INH was used as a sole agent, instances
of hepatotoxicity appeared suggesting that when
given in combination therapies ,the combination
of drugs may have been associated with a
reduced production of intermediate metabolites
of INH.
Isoniazid Hepatotoxicity -3




Elevations of aminotransferase levels from INH usually
appear within several weeks following initiation of
treatment and are found in 10% to 20% of patients.
Usually, these elevations are modest and not associated
with signs or symptoms suggestive of liver disease.
In many (likely most) patients, continued use of INH
is well tolerated and often the aminotransferase levels
return to or near normal.
If INH is discontinued when the elevations are noted,
the aminotransferase levels generally return to normal
within 1 to 4 weeks.
Isoniazid Hepatotoxicity -4




However, a few patients receiving INH develop
significant clinical hepatitis, and drug-induced
hepatic failure may occur (0.1%-2.0%)
Patients older than 50 years are at an increased
risk of developing clinically evident hepatitis
from INH.
Children rarely manifest any clinically evident
liver disease from INH.
Women are more likely to be severely affected
than men.
Isoniazid Hepatotoxicity -5
 Presently,
patient-monitoring schedules with
discontinuation of treatment in those in whom there are
significant or rising levels of aminotransferases are
recommended and appear to be effective.
Isoniazid Hepatotoxicity -6



The liver injury from INH appears to be
mediated by toxic metabolic products, including
hydrazine and monoacetyl derivatives formed
during metabolism.
There are generally no signs or symptoms
suggestive of hypersensitivity.
INH is metabolized by N-acetyltransferase and
CYP 2E1 to form reactive intermediates.
Isoniazid Hepatotoxicity -7


In the first phase, isoniazid is metabolized by Nacetyltransferase (NAT2) to acetylisoniazid,
which is then hydrolyzed to acetylhydrazine.
Acetylhydrazine is further metabolized by CYP
2E1 to produce hepatotoxic derivatives.
Isoniazid Hepatotoxicity -8



In a study from Taiwan of 318 patients who had
tuberculosis and were receiving INH, the
genotypes of CYP 2E1 and NAT2 were
determined by a restriction fragment length
polymorphism method.
Forty-nine (5.4%) of the patients showed some
evidence of hepatotoxicity.
The risk of hepatotoxicity based on CYP 2E1
activity and the acetylator status (rapid or slow)
was analyzed.
Isoniazid Hepatotoxicity -9




The wild-type allele for CYP 2E1 is c1.
The risk of hepatotoxicity was 3.94 for CYP 2E1
c1/c1 with rapid acetylation status to 7.43 for CYP 2E1
c1/c1 with slow acetylation.
Even after adjustment for acetylation status, CYP 2E1
c1/c1 was an independent risk factor for hepatotoxicity
(P = 0.017).
Volunteers who were CYP 2E1 c1/c1 had higher
CYP2E1 activity than those with c1/c2 or c2/c2,
suggesting accelerated production of hepatotoxins
Isoniazid Hepatotoxicity -10


Possible induction of CYP 2E1 by alcohol may
explain the increases in INH hepatotoxicity seen
in regular to heavy users of alcohol.
Based on these studies, determination of the
CYP 2E1 phenotype before institution of
isoniazid therapy may prove clinically useful.
Troglitazone Hepatotoxicity-1



Troglitazone, a thiazolidinedione agent that is a PPAR[gamma] agonist used in the treatment of diabetes, was
withdrawn from the market after early extensive use
when several instances of acute liver failure leading to
death or the need for liver transplantation were
identified
A debate has ensued as to whether there was a signal in
the prerelease clinical trials, which indicated likely major
hepatotoxicity. In the trials,
2510 patients received the drug- Two developed
jaundice and 1.9% had aminotransferase elevations of
>3 times ULN as compared with 0.6% in patients who
received placebo
Troglitazone Hepatotoxicity-2



The hepatic injury in patients who developed
liver injury was predominantly hepatocellular.
The mechanism for troglitazone-induced liver
injury has not been established.
Other PPAR-[gamma] agonists (rosiglitazone
and pioglitazone) have been associated with
hepatotoxicity in rare instances.
Statins Hepatotoxicity-1






Few drugs have been as widely prescribed as the statins.
There have been lingering concerns regarding statininduced hepatotoxicity from the time of introduction in
1987 of lovastatin, the first member of the class.
Millions of patients have now received these drugs.
Asymptomatic increases in aminotransferase levels
develop frequently.
Elevations to >3 times upper limit of normal occur in
1% to 3%.
Statins Hepatotoxicity-2



In one study, 127 of 6,605 patients treated with
lovastatin had ALT elevations of 1.5 to 3 times
the upper limit of normal
The elevations in ALT generally return to or
toward normal despite continued therapy.
There have been remarkably few welldocumented instances of statin-induced severe
liver injury.
Statins Hepatotoxicity-3



There is evidence that suggests the increases in
aminotransferases may represent a pharmacologic
effect associated with lipid lowering.
An intracellular accumulation of precursors following
HMG-CoA reductase inhibitors may lead to
enlargement of hepatocyte and to ALT increases.
Exactly how lowering cholesterol or favorably affecting
the lipid profile is associated with aminotransferase
elevations remains unknown.
Statins Hepatotoxicity-4




There is no evidence that patients who have elevated
baseline ALT levels associated with diabetes,
steatohepatitis, or chronic hepatitis C are at increased
risk.
Therefore, present evidence supports the concept that
statins are hepatically safe agents despite the rather
frequent elevations of ALT.
Again, this supports the concept that mild to moderate
elevations of ALT do not equate to liver injury.
There is scant support for following a regular
biochemical monitoring schedule in patients receiving
statins.
Minocycline Hepatotoxicity-1


Minocycline, a semisynthetic derivative of
tetracycline that has been widely used in the
treatment of acne, has been reported to cause
acute hepatitis, a chronic hepatitis with
autoimmune features, and a systemic lupus
erythematosus syndrome.
Several deaths from liver disease have occurred.
Minocycline Hepatotoxicity-2


Positive rechallenges with recurrence of liver
disease have been observed.
The autoimmune hepatitis syndrome, which is
more frequently observed in females who have
received the drug for months to more than a
year and is characterized by the presence of
fever, arthralgias, hyperglobulinemia, antinuclear
antibodies, and a liver biopsy indistinguishable
from classic type autoimmune hepatitis
Minocycline Hepatotoxicity-3




It is important for the clinician to recognize the role of
minocycline and withdraw the drug, which usually leads
to rapid improvement.
If the patient is considered to have Type 1
autoimmune hepatitis and is treated with
corticosteroids while minocycline is continued, there is
a risk of partially masking the drug-induced injury.
This masking was the case with methyldopa-induced
chronic hepatitis and oxyphenistatin-induced chronic
hepatitis.
The mechanism of minocycline-induced liver injury is
unknown.
HERBAL HEPATOTOXICITY-1




There has been increasing recognition that herbal
products of many types can cause hepatotoxicity.
Patients who have underlying liver disease often use a
variety of herbals as alternative medicines.
Milk thistle (silymarin) has been widely embraced by
patients with hepatitis C, despite lack of extensive
controlled studies supporting benefit.
Fortunately, there is equally scant evidence of any
hepatotoxicity from the compound.
HERBAL HEPATOTOXICITY-2




Acute hepatitis and acute liver failure have been
reported with a number of compounds including kava.
There are special difficulties in associating an herbal
product with hepatic injury.
These include problems in obtaining an accurate history
of ingestion and often an unwillingness of the patient
to fully disclose what has been ingested.
Traditional and alternative treatment regimens abound
throughout the world. These products may vary from
lot to lot and are not manufactured to approved
standards
HERBAL HEPATOTOXICITY-3



Extracts of kava-kava, a plant in the pepper family, has
been used as a beverage for centuries by South Pacific
islanders for reducing anxiety and as a remedy for
sleeplessness and menopausal symptoms.
More recently, standardized extracts of kava-kava
containing concentrated extract have been produced in
Europe and subsequently introduced into the United
States. Instances of acute hepatic failure and death have
been attributed to kava-kava.
The commercially available standardized extracts that
have caused liver injury contain 30% to 70% lactones
VITAMIN A (Retinol )HEPATOTOXICITY-1


Excessive ingestion of vitamin A is an
established cause of liver disease leading to
cirrhosis with ascites and portal hypertension.
Chronic ingestion of large amounts of vitamin
A often used as part of the megavitamin
generalized health protection programs can lead
to chronic intoxication and liver injury.
Vitamin A Toxicity
VITAMIN A HEPATOTOXICITY-2




Hypervitaminosis A most often results from
self-medication.
The usual recommended dose of vitamin A for
adults is 5,000 IU per day.
Hepatic injury has been seen in patients who
received 15,000 to greater than 40,000 units a
day for a period of years.
Even higher doses may produce signs of
intoxication within several months..
VITAMIN A HEPATOTOXICITY-3


The liver is a principal storage site for retinol and, more
specifically, the stellate cells bear the brunt of the
attack.
Many patients with liver injury from ingesting excessive
vitamin A go unrecognized, and only an astute clinician
is likely to make the association between chronic
ingestion of vitamin A and otherwise unexplained
advanced hepatic disease with cirrhosis, ascites, and
portal hypertension
VITAMIN A HEPATOTOXICITY-4



The clinical picture most often is one of insidious onset
of cirrhosis.
Elevations of aminotransferases are found in over 70%
of patients with vitamin A-induced liver injury, along
with slightly elevated levels of alkaline phosphatase and
occasional minimal to modest elevations of serum
bilirubin.
In patients with advanced vitamin A intoxication,
hypoalbuminemia and hypoprothrombinemia are
present.
VITAMIN A HEPATOTOXICITY-5




Vitamin A is stored in stellate cells.
A syndrome of hepatoportal sclerosis with portal and
perisinusoidal fibrosis as well as sclerosis of terminal
venules and atrophy of zone 3 of the hepatic lobule are
characteristic findings.
Portal hypertension results from the compromising of
sinusoids by the enlarged stellate cells as well as by
fibrous tissue deposited in the sinusoids and the
sclerosis of the terminal venules.
Occasionally microvesicular steatosis is found.
VITAMIN A HEPATOTOXICITY-6





Vitamin A-induced hepatic injury apparently results
from the intrinsic toxicity of vitamin A, and the extent
of the injury depends on the dose and duration of
exposure.
The increased levels of vitamin A in stellate cells lead
to multiplication of the cells and conversion to
myofibroblasts.
Alcoholic patients appear to be unusually susceptible
to vitamin A intoxication.
Alcohol potentiates the toxicity of vitamin A in
experimental situations.
The treatment is withdrawal, and the diagnosis
depends on careful history taking and awareness
Acetaminophen
(APAP)
Budget
suicide: cheap,
accessible, popular
80% OD’s > 15 g
Toxic dose >150mg/kg (~6g)
S. levels useful 4-15 h out
Nomogram: know it, use it
APAP
Dose-dependent
production
of toxic metabolite (NAPQI)
produced
by P450
conjugated by glutathione
O
Cytochromes P450 lead to
unstable compounds!
C
HN
O
O
C
C
HN
N
CH3
CH3
CH3
SG
OH
Cytochrome p450 2E1
Mercapturic Acid
(nontoxic)
(phase I)
OH
O
NAPQI
(highly reactive intermediate)
(phase II)
Hepatocyte Damage
•Covalent binding to cell proteins,
including enzyme itself
•ADDUCTS
Nontoxic Metabolites
•Derangement of apoptosis?
•CAR?
APAP
NAPQI
directly cytotoxic
Hepatic
Renal
“Will tylenol taken
with EtOH prevent
hangover?”
EtOH
Use
Increased
p450 = more NAPQI
EtOH metabolism depletes
glutathione stores = more
NAPQI
APAP
Labs
gone wild
Transaminitis
Hyperbilirubinemia
Coagulopathy
(INR)
ATN
+
/ - myocardial necrosis
APAP
NAC
– glutathione substitute
load
140 mg/kg PO
17 doses over 72 h
Can give by NGT / IV
Charcoal
if < 4 h
Antiemetics prn
APAP
NAC
Best
within 8-10 h
Still useful > 24 h
Give first, ask questions later!
Drug-Induced Liver Disease

Predictable


Dose-related
Unpredictable
Not dose-related
 Immune-mediated
 Idiosyncratic

Bile

Composed of bile salts, glutathione,
phospholipids, cholesterol, bilirubin, organic
anions, proteins, metals, ions, xenobiotics

Bile formation essential for:

lipid uptake from small intestines

Protection of small intestines from oxidative injury

Excretion of endogenous and xenobiotic
compounds
Bile Excretion


Metals

Uptake (facilitated diffusion vs. receptor)

Excretion (lysosomes, transporters)

Copper, manganese, cadmium, selenium, gold, silver, arsenic
ATP-dependent exporters

MDR (multiple-drug resistance)

cMOAT (canalicular multiple organic ion transporter)
Bile Formation
Metals
Bile Salts Bilirubin
cMOAT
Conjugates of glutathione,
glucuronide, sulfate
Bile
Canaliculi
Drugs,
hormones,
xenobiotics
MDR
Organic cations,
drugs, phospholipids
Bile Excretion
Enterohepatic
Cycling
Canaliculi
Channels
Bile Ducts
Common Bile Duct
Small Intestine
Zones of Oxygenation of The Liver
Fatty Degeneration


Increased lipid content of the hepatocytes (liver
parenchymal cells) steatosis
Etiology (cause) can be nutrition and it can be due to a
toxic substance




Over supply of fatty acids (FA)
Alteration of triglyceride cycle
Increase FA synthesis
Decrease aproprotein synthesis
Characterization and Classification
Clinical Pathology
Morphologic Pathology
Mechanistic Pathology
Appropriate
Hepatobiliary
Injury
Classification
Fatty Degeneration (cont)


Toxic substances
Liver may be enlarged
Ethionine – metabolic inhibitor
 Valproic acid

Hepatocellular Necrosis


Necrosis and apoptosis
Necrosis





Nucleus is often marginated
Cell swells
Leakage of cytoplasm
Pyknosis of the nucleus
Karyorrhexis
Liver Necrosis

Leakage of cytoplasm

Enzymes in the hepatocyte are leaked into systemic
circulation, for example
Aspartate aminotransferase
 Alanine aminotransferase
 Sorbitol dehydrogenase
 Forms of lactic acid dehydrogenase

Hepatocellular Necrosis



Histopathology is evident for days after the
hepatocytes have died.
Described by the area of the hepatic cords or
the lobule (acinus) that has undergone necrosis
Toxic substances can produce necrosis in certain
areas

Eg, CCl4 is zone 3 or centrilobular
Canalicular Cholestasis





Decrease in volume of bile or impaired secretion of
bile
Patient is jaundice
May be bile plugs in the bile ducts
Have elevated bilirubin, icterus index, ect
Toxic substances



Chlorpromazine
Cyclosporin
Estrogens
Canalicular Cholestasis

Decrease in the volume bile formed or impaired
secretion of solutes into bile

Compounds found in bile will be elevated in blood
(eg bilirubin  jaundice)
Cholestasis
Chlorpromazine: 1, 4
Estrogen: 1, 2
Manganese: 6
1
5
2
6
3
4
Bile Duct Damage



Cholangiodestructive cholestasis
Increased serum activity of gamma
glutamyltransferase (GGT) and other enzymes
Damage to epithelium of bile ducts

Increased cells - hyperplasia
Aflatoxins
 Pyrrolizidine alkaloids

Bile Duct Damage (Cont)

Damage to epithelium of bile ducts (cont)

Necrosis of bile duct cells

Sporidesmin


A mycotoxin
Methylene dianiline


Human exposure in contaminated flour
Mistaken for a drug of abuse
Sinusoidal Damage



Fenestration of endothelium for high
permeability
Fills with blood
Occurs with veno-occlusive disease

See with fibrosis of the liver


Pyrrolizidine alkaloids
Cyclophosphamide

After GSH is used up
Sinusoidal Damage
Cirrhosis


Progressive liver injury
Accumulation of fibrous tissue





Collagen fibers
Around central vein
Space of Disse
Result of repetitive damage of liver cells
Humans


EtOH abuse
Chronic aflatoxicosis
Liver Neoplasms

Primary neoplasm


Neoplasm from cells in the liver
Secondary neoplasm

Neoplasm outside the liver
Invasion
 Metastasis


Aflatoxins

Hepatocellular carcinomas
Uptake of Toxic Substances

First Pass Effect


Microcystin


Term used to describe the rapid uptake of some
chemicals by the liver
Blue-green algae
Plalloidin
Amanita phalloides
 Block uptake with cyclosporin A

Bioactivation

EtOH
EtOH rapidly metabolized by alcohol dehydrogenase
to acetaldehyde
 Acetaldehyde metabolized slowly by aldehyde
dehydrogenase to acetate


Balance of Phase 1 and Phase II
biotransformation reactions
Major Cell Types

Hepatocytes (parenchymal)


Endothelial Cells


line sinusoids – small - form fenestrate (pores) -  25% of lobule
Ito (stellate) Cells


large -  75% of lobule
store fat – store & metabolism, vitamin A - synthesize collagen
Kupffer Cells

few – phagocytic - immune - can release active molecules and secrete
cytokines, present antigens
DILI Diagnosis

DILI is a diagnosis of exclusion based on
circumstantial evidence due to lack of
objective confirmatory lab test, rechallenge,
or “GOLD” standard


Requires a high index of suspicion
DILI diagnosis is usually retrospective
Exclude other causes
 Dechallenge requires follow-up

Bile Formation
Metals
Bile Salts Bilirubin
cMOAT
Conjugates of glutathione,
glucuronide, sulfate
Bile
Canaliculi
Drugs,
hormones,
xenobiotics
MDR
Organic cations,
drugs, phospholipids
Blood Supply to The Liver



The venous blood from the majority of the
gastrointestinal tract and peritoneum flows to
the liver in the hepatic portal vein.
Hepatic artery is small and supplies arterial
blood to the liver
Blood from the liver empties into the vena cava
below the heart
Issues: Idiosyncratic Drug
Toxicity
Occurs despite careful preclinical testing in
animals
 … and despite careful and costly clinical trials
 Some problem (perhaps wrong) assumptions:





Assuming drug variability is the key to safety
Obsolete concepts of “safe and effective” – for all?
Assuming one dose/regimen suits all patients
Focus on efficacy, little on safety (especially if rare)
Cholestasis
Chlorpromazine: 1, 4
Estrogen: 1, 2
Manganese: 6
1
5
2
6
3
4
Cholestasis
Chlorpromazine:
Estrogen
1
5
2
6
3
4
Types of Liver Injury








Hepatocellular death
Fatty degeneration
Canalicular cholestasis
Bile duct damage
Sinusoidal damage
Damage to cytoskeleton
Cirrhosis
Neoplasm