L37 - Drug Elimination - Metabolism 2

Question 1

What is hepatic extraction ratio defined as?

Answer 1

• fraction of drug passing by liver which is eliminated
• ratio between rate of hepatic elimination and rate of presentation of drug to the liver

Question 2

What is the eqn for hepatic extraction rate?

Answer 2

Eh = rate of elimination / rate of presentation
= Centering - Cleaving)/Centering

Question 3

What is the eqn for rate of drug presentation?

Answer 3

Qh x Centering

Question 4

What is the eqn for drug elimination?

Answer 4

Qh x (Centering - Cleaving)

Question 5

What and when does the extraction ratio range?

Answer 5

• 0, drug not eliminated / Centering = Cleaving
• 1 all drug eliminated / Cleaving = 0

Question 6

What is the hepatic extraction ratio a measure of?

Answer 6

The liver efficiency in eliminating the drug from the systemic circulation over a single pass through the organ

Question 7

What does hepatic clearance (CIh) measure?

Answer 7

The loss of drug across the liver

Question 8

What can CIh be defined as?

Answer 8

• volume of blood entering the liver from which all the drug is removed per unit time
• ratio between hepatic elim rate and incoming conc

Question 9

What does some drugs the time required for…?

Answer 9

• leaving blood cells
• dissocating from plasma proteins
• diffusing hepatic membranes
• being metabolised
• being transported to bile