GI: Drugs and the Liver Flashcards
What is the usual option for cholelithiasis?
Surgery
What can be used to resuce the itch in cholelithiasis?
ursodeoxycholic acid
What is the pain relief treatment of biliary colic?
Analgesia - morphine, buprenorphine
What relieves biliary spasm in biliary colic?
Atropine
GTN
Why might morphine not be the best choice of pain relief in biliary colic?
Contricts the sphincter of oddi
What happens to drugs that are metabolised in the liver?
Convert parent drugs to more polar metabolies that are not readily reabsorbed by renal tubules, facilitating excretion
What can occasionally happen in liver metabolism?
Metabolites may gain activity (prodrugs) Unchanged activity (diazepam) Posses a different type of activity
What are the two phases of liver drug metabolism?
Phase I= oxidation, reduction, hydrolysis- makes drug more polar
Phase 2= conjugation- adds an endogenous compound - more polar
Give an example of drug metabolism.
Aspirin–>Salicylic Acid–>Glucuronide
What happens to the metabolic function of the liver in cirrhosis?
Decreased
Decreased plasma proteins and blood flow
Give examples of highly metabolised drugs
GTN
Phenytoin
Calcium channel blockers
What substances build up and are not properly metabolised in liver cirrhosis
aldosterone
oestrogen
endothelin
What happens if you give calcium channel blockers in cirrhotics?
Gut oedema
impaired renal and liver function
ascites
CHF
What are the consequences of giving NSAIDs in cirrhotics
recreased renal prostaglandin= renal impairment and failure
increased peptic ulcer which is a bleeding risk
How should you prescribe NSAIDs in cirrhotic
With a PPI
Name drugs which have a reduced metabolism in the liver in cirrhotics
Opiates Calcium channek blockers benzodiazepines chloromethiazole cyclosporin metronidazole
Why can paracetamol be toxic in the liver
It breaks down to a highly reactive intermediate called GLUTATHIONE
Becomes toxic at normal doses in liver cirrhotics
How should paracetamol be prescribed in cirrhotics?
1g twice daily
No more than 3g
Codeine 30mg twice daily
AVOID NSAIDs
What antibiotics can induce hepatitis
amoxicillin and clavulanic acid
What is Hy’s Law?
If ALT/AST more than five times the upper limit of normal
and bilirubin more than 3
= risk of a drug causing liver injury
What is the best diuretic to use in ascites in liver cirrhosis
spironolactone
What antibiotics can be nephrotic
aminoglycoside eg gentamicin
Which antibiotics can be epileptogenic
Quinolone
What antibiotics have reduced metabolism in cirrhotics
metranidozole
