One-Compartment Model - IV Bolus Dose

Question 1

when a drug is given at 10mg intravenously, the disposition kinetics of a drug can be described by C = 10exp(-0.4t), where C in mcg/L and t in time. If the dose is doubled, what would the C = f(t) become?

Answer 1

C = 20exp(-0.4t). Since concentration is directly proportional to dose and k is independent of dose, C0 = 2- mcg/L and k remains unchanged when dose is doubled

Question 2

Steps to calculate CL based on 2 concentration-time points. Assume 1C model with 1st order elimination

Answer 2

Step 1: k = ln(C1/C2)/(t2-t1)
Step 2: C0 = C1exp (+kt1)
Step 3: V = D/C0
Step 4: CL = V*k
- make sure to convert the amount units in D to the same amount units in C if needed

Question 3

How does change in V affect AUC?

Answer 3

Change in V does not affect AUC because AUC is inversely related to CL and CL has no relationship with V

Question 4

If the dose is doubled, time for 30% dose to be eliminated should be _______ (doubled/halved/unchanged)

Answer 4

unchanged (trick: time does not have an amount in its units and is thus independent of dose)

Question 5

If the dose is halved, concentration at time 0 should be ________ (doubled/halved/unchanged)

Answer 5

halved (concentrations at any time point should be proportional to dose)

Question 6

If the dose is doubled, the fraction of dose remaining at 2 hours after dosing should be ________ (doubled/halved/unchanged)

Question 7

If the dose is doubled, the fraction of dose remaining at 2 hours after dosing should be _________ (doubled/halved/unchanged)

Question 8

T/F - For systemic therapy, blood is usually considered the central compartment

Answer 8

true

Question 9

T/F - For systemic therapy, adipose tissues are often considered part of the peripheral compartment

Answer 9

False - we usually do not specify which organ/tissue belongs to which compartment

Question 10

For tissues or organs to be lumped into the same compartment, they should have the same ________ (concentration/binding affinity for proteins/blood flow rate/concentration declining half-life)

Answer 10

concentration declining half-life (or pharmacokinetic behavior)

Question 11

In multi-compartment PK models, ________ is always included in the central compartment

Answer 11

blood/plasma

Question 12

T/F - Given the presence of blood-brain barrier, brain is usually considered part of the peripheral compartment

Answer 12

False - PK compartment models have vague biological feature in that we don’t specify which organ or tissue should belong to which compartment

Question 13

Tissues or organs in the same PK compartment should have the same ________ (drug concentration/binding affinity for the drug/blood flow rate/pharmacokinetic behavior)

Answer 13

pharmacokinetic behavior