drug induced liver injury for undergraduates

1. Drugs & Liver
Drug-Induced Liver
Injury (DILI)
PROF. DR. MOHAMED-NAGUIB WIFI
PROFESSOR OF MEDICINE AND
HAPATOGASTROENTEROLOGY
CAIRO UNIVERSITY

2. • The liver is the major site of drug
metabolism.
• Drugs are converted from fat-soluble to
watersoluble substances that can be
excreted in the urine or bile.
• Drug induced liver injury is the most
common cause of abnormal liver
function tests, and a high index of
suspicion should be thought specially
after exclusion of other causes.
Drugs & The Liver

3. •Damage to the liver by
drugs (drug-induced liver
injury, DILI) is usually
classified as being either:
•Predictable (dose-related)
•Non-predictable (not dose-
related)
Drug Hepatotoxicity

4. • At least six mechanisms may be involved in the production of
damage:
1. disruption of intracellular calcium homeostasis
2. disruption of bile canalicular transport mechanisms
3. formation of non-functioning adducts (enzyme–drug), which may then lead
to
4. presentation on the surface of the hepatocyte as new immunogens (attacked
by T cells)
5. induction of apoptosis
6. inhibition of mitochondrial function, which prevents fatty acid metabolism
and accumulation of both lactate and reactive oxygen species.
Mechanisms of DILI

6. •The predominant mechanism or
combination of mechanisms determines
the type of liver injury: that is, hepatitic,
cholestatic or immunological (skin
rashes, fever and arthralgia, i.e. serum
sickness syndrome). Eosinophilia and
circulating immune complexes and
antibodies are occasionally detected.
Patterns of DILI

7. • When a small amount of hepatotoxic drug whose
effect is dose-dependent (e.g. paracetamol) is
ingested, a large proportion of it undergoes
conjugation with glucuronide and sulphate.
• The remainder is metabolized by microsomal
enzymes to produce toxic derivatives that are
immediately detoxified by conjugation with
glutathione.
• If larger doses are ingested, the former pathway
becomes saturated and the toxic derivative is
produced at a faster rate.
• Once the hepatic glutathione is depleted, large
amounts of the toxic metabolite accumulate and
produce damage.
Pathophysiology

9. •Presentation may vary from
fulminant liver cell failure to
minor lab. abnormalities in
liver function tests.
Clinical Presentations

10. •A high index of suspicion
•Exclusion of other causes of liver injury
•History of ingestion of a drug (not often
obvious; a drug reaction may occur within 3-6
months from the start of a drug)
•Toxicology screen
•Liver biopsy is not often diagnostic
Diagnosis

11. •Stop the drug
•Specific antidote( e.g. N-acetylcysteine
for acetaminophen overdose)
•Conservative and symptomatic treatment.
•Plasmapharesis
•Liver transplantation in cases of drug
induced fulminant liver cell failure.
Therapeutic Options

12. •The metabolism of drugs is impaired in
severe liver disease (with jaundice and
ascites), as the removal of many drugs
depends on liver blood flow and the
integrity of the hepatocyte.
•In general, therefore, the effect of drugs is
prolonged by liver disease and also by
cholestasis.
Drug prescribing for patients with liver disease

13. •This is further accentuated by
portosystemic shunting, which diminishes
the first-pass extraction of drugs.
•With hypoproteinaemia, there is
decreased protein binding of some drugs,
and bilirubin competes with many drugs
for the binding sites on serum albumin.
Drug prescribing for patients with liver disease

14. •encephalopathy, care must be taken in
prescribing drugs with a central
depressant action, such as narcotics like
codeine and anxiolytics.
•Other common drugs to be avoided in
cirrhosis include angiotensin-converting
enzyme (ACE) inhibitors (which cause
hepatorenal failure) and NSAIDs (which
cause bleeding).
Drug prescribing for patients with liver disease