drug metabolism Flashcards
Where is the primary place the body eliminates a water soluble drug from the body
Liver or kidney
How would you adjust drug dosage if eGFR is lower than it should be
Reduce dosage
How can’t lipid soluble drugs be removed from the body
Liver or kidney so it is the purpose of drug metabolism to break down the drug to make it more water soluble
How are volatile drugs excreted
Lungs
What is the role of cytochromep450
Starts metabolism of drugs to make it ready for excretion by making it more reactive
What can cytp450 do
inactive/activate drugs
How is paracetamol removed from body and why is too much toxic
Forms NAPQI which is a toxic metabolite. It is mopped up by glutathione in the liver. However if you exceed safe levels. napqi is toxic to proteins in liver and toxic to kidneys too.
What is the antidote for paracetamol overdose
N-acetylcysteine (treat within first 8 hours)
What is the route of drug metabolism
Phase 1- introduction or unmasking or functional group to make it more reactive for phase 2. Involves cytochrome p450
Phase 2- conjugation reaction. Binds more reactive phase 1 product to glutathione to increase water solubility
Why is it a complication if a drug is able to get metabolised by different cytochrome pathways
Harder to see interactions with other drugs because drug is getting metabolised by different pathways
How is alcohol metabolised
Alcohol dehydrogenase metabolises it to aldehyde and that turns to ethanoic acid
What is an antibiotic that will interact with the pathway that metabolises alcohol
Metranidazole so aldehyde does not turn to ethanoic acid and so this makes patient ill
What is glucuronidation
Adding glucuronic acid which promotes the excretion of the metabolites
When would there be variations in metabolism
Age (reduced level of drug metabolism at both extremes of age)
Liver disease (decreased metabolism in acute viral hepatitis and chronic liver disease)
Pharmacogenetics (SNPs affecting cytp450. Have higher than normal drug concentrations as they are slow metabolisers)
Why do MABs have long half lives
Because they stay as large molecules in circulation. Broken Down by proteolysis instead of CP450
