Drug Metabolism and Hepatic Circulation Flashcards
What are the two blood supplies the liver has?
Right and Left hepatic arteries.
Portal Vein
Where does all the blood from the gut pass into?
Passes via the portal vein into the liver.
Where does 20% of the cardiac output pass into? And where does it travel through?
Passes through the liver and does so, by travelling through the hepatic artery.
What is the order of drug exposure?
1) Portal Vein
2) Liver Sinusoids
3) Hepatic Vein
4) Hepatic Artery
5) Common Bile Duct
What the two examples of drug administration which bypasses the liver?
Sublingual
Buccal
These two go straight into the systemic veins
Which location are drugs normally metabolised in?
Hepatocytes.
What does Phase I of the metabolism of drugs involve?
Cytochrome P450 enzymes = These are used in order to allow oxidation / reduction / hydrolysis / hydration to occur.
What does Phase II of the metabolism of drugs involve?
Conjugation Pathways.
These are used in order to make the drug water soluble in order to be eliminated.
Where is the tissue expression of cytochrome P450 enzymes the greatest?
The Liver.
What is bioavailability?
Fraction of dose that reaches the systemic circulation unchanged.
What is the equation for bioavailability?
𝐹= AUC (oral) / AUC (iv)
Where must drugs be metabolised by enzymes?
In the gut wall and / or liver.
What reduces bioavailability?
Significant first pass metabolism.
What routes can be used in order to avoid first pass metabolism?
Buccal
Sublingual
Rectal (Is a possibility?)
What happens to bile salts?
Reabsorbed from the small intestine and then, circulates back to the liver in the portal vein.
