Liver disease and drug handling Flashcards
metabolic reactions are either what phases?
Phase 1/ 2
Example of phase 1 reactions
Oxidation
Hydroxylation
Dealkylation
Deamination
Hydrolysis
Is phase 1 reactions anabolic/ catabolic?
catabolic —> breaking down of drug
Is phase 2 reactions anabolic/ catabolic?
anabolic : (conjugation)
Aspirin metabolic reactions : phase 1/phase 2
Phase 1 creates salicylic acid and Phase 2 creates a water-soluble molecule for excretion
what phase (1/2) drug reactions are affected more by increase in age?
Phase 1 drug reactions affected more than Phase 2
renal function can lead to reduced excretion of drugs. how? some factors
renal blood flow, filtration, renal mass decrease with age
Co-morbidities contribute to this decline
prothrombin time define:
how long it takes for clot to form
rifampicin induces what enzyme?
CYP2C9
Omeprazole inhibits what enzyme?
CYPC219
Omeprazole by inhibiting CYP2C19 this has what effect on clopidogrel?
prevents the production of active metabolite of clopidogrel
Rifampicin induces and enzyme. This has what effect on warfarin?
reduces anti-coagulant effect of warfarin
Liver metabolises?
carbohydrates (glycogen)
protein
lipids
Example of causes of liver disease?
alcohol, obesity, viral hepatitis
Stages of liver damage
healthy liver –> liver steatosis –> fibrosis liver —> cirrhosis liver –> liver cancer
wilsons disease is?
inherited disorder- accumulation of copper
Hemochromatosis disease is?
inherited disorder- Accumulation of iron
Examples of unusual cases that cause liver disease
tropical infections
TB
syphilis
lymphoma
example of drug-induced liver injury : DILI
Paracetamol
NSAID
Antidepressants
steps of drug-induced liver injury : DILI (detail)
- Inhibition of mitochondrial function–> preventing fatty acid metabolism, & accumulation of lactate & reactive oxygen species
- Disruption of bile canalicular transport mechanisms
- Disruption of intracellular homeostasis
- Formation of non-functioning adducts which may then lead to
…presentation on the surface of hepatocytes as new immunogens (attacked by T-cells) - Induction of apoptosis
steps of drug-induced liver injury : DILI ( simplified)
- Mitochondrial impairment
- Inhibition of biliary efflux
- Lysosome impairment
- Reactive metabolites
- Endoplasmic reiticulum stress
- Immune system
Drug- induced liver injury can either be:
intrahepatic
extrahepatic
intrahepatic define:
involving hepatocytes
extrahepatic define:
outside hepatocytes
signs of intrahepatic DILI
often an immune-mediated response to a drug
May be asymptomatic and may be associated with features of drug hypersensitivity e.g: skin,rash,fever
symptoms of intrahepatic DILI
Nausea, vomiting, anorexia, jaundice, right upper quadrant pain
signs of extrahepatic DILI
Jaundice, itching (due to accumulation of bile salts)
Extrahepatic DILI also called? What is it?
Also called cholestasis
Reflects the inability of liver to remove bile from body due to blocked biliary ducts
Symptoms of extrahepatic DILI
May be asymptomatic
Intrahepatic vs extrahepatic
Intrahepatic = often an immune-mediated response to a drug
Extrahepatic = reflects the inability of liver to remove bile from body due to blocked biliary ducts
Why might a patient experience disorientation/ confusion from DILI?
Liver is unable to get rid of toxic metabolites which can cause them to be confused
Liver function test: for hepatocellular damage
ALT
AST
Liver function test: choleostasis, impair conjugation or biliary obstruction
Bilirubin
ALP
Liver function test: synthetic function
PT
Albumin
Liver function test: choleostasis or biliary obstruction
GGT
Bile acids
5- nucleotides
AST ? Present also where?
Aspartate aminotransferase
Present in the heart, muscle, kidney, brain
ALP? Present also where?
Alkaline phosphatase
Present in placenta, bone
ALT? Present also where?
Alanine aminotransferase
More specific to the liver
GGT? Present also where?
Gamma-glutamyltransferase
Present in kidney, pancreas, heart, brain
- chronic ethanol consumption
Raised ALP but normal GGT/ and or bilirubin, indicates?
Increased bone turnover/ vitamin D deficiency / bone fractures
Amino transferases are?
Enzymes contained in hepatocytes that leak into blood when cells are damaged
Raised ALT/ ATP indicates?
Hepatic
Raised ALT/ AST indicates?
Viral hepatitis
- specific for liver injury + good marker for acute liver injury
Raised AST/ ALT indicates?
Alcohol liver disease/ NAFLD / cirrhosis
- but also raised in myocardial infarction/ burns / trauma
Raised ALP / GGT and /or bilirubin
Cholestatic
(Gall stones blocking the bile duct / induced medication)
Low albumin levels indicates?
Reduced synthetic function of the liver
Raised PT/ INR indicates?
prolonged clotting and reduced synthetic function in context of liver disease
Albumin levels can be low by other causes, examples?
Malnutrition, sepsis
What should be excused as the cause of a prolonged PT?
Vitamin K deficiency
Prothrombin time indicator of?
Acute and chronic liver disease
What treats coagulation factors?
Prothrombin
% Of cardiac output that passes through the liver?
20%
Liver metabolism can produce what? (Negative)
Toxic metabolites
Paracetamol metabolism
Phase 1 metabolism: by CYP450 isoforms to form NAPQI
- NAPQI detoxifies through conjugation with glutathione
Phase 2: metabolism = conjugation with glucoronide, sulphate
- since non-toxic metabolites = elimination via kidneys
Phase 2: metabolism = conjugation with glucoronide, sulphate of paracetamol is eliminated via the kidneys. Why?
Non-toxic metabolite
If paracetamol taken in overdose, what happens in metabolism?
Paracetamol into phase 2 metabolism becomes saturated = more goes into phase I metabolism
= more NAPQI formation = more hepatotoxic and nephrotoxic ( can’t be eliminated via kidneys)
Dose - related toxicity is what type of ADR/ adverse drug reaction?
Type A ( augmented)
How can NAPQI cause renal failure?
Bind renal cells
NAPQI is highly reactive. This can have what effect?
Oxidises key enzymes causing cell death
What is given for paracetamol overdose? And mechanism.
N acetyl cysteine (NAC)
Replenishes glutathione to get rid of excess NAPQI
So it can carry on to phase 2 to be eliminated in the kidneys
Unpredictable, ‘idiosyncratic’ is what type of ADR?
Type B (bizarre)
Excessive drinking of alcohol leads to metabolic tolerance and increased levels of acetaldenyde. How?
Acetyladehyde dehydrogenase becomes fully saturated with alcohol leading to buildup of acetyladehyde
Chronic exposure to drug is what type of ADR?
Type C
Why avoid opioids in liver failure?
Central depressant action in patients with hepatic encephalopathy
Why avoid diuretics in liver failure?
Dehydration= Increased risk of hepatic encephalopathy
Why avoid warfarin in liver failure?
Enhances effects
Why avoid NSAIDs in liver failure?
Increased risk of bleeding
Why avoid oral hypoglycaemics in liver failure?
Loss of glucose homeostasis
Increased risk of lactic acidosis
Why avoid ACE inhibitors in liver failure?
Hepatorenal failure
Drugs to avoid in liver failure : examples
Warfarin
opioids
Oral hypoglycaemics
Ace inhibitors
Diuretics
NSAIDs
Ammonia toxin accumulating in blood =
Hepatic encephalopathy
DILI: Methotrexate can cause what type of liver damage?
Fibrosis
DILI: paracetamol can cause what type of liver damage?
Acute hepatic necrosis