PHA 5127

Problem Set
"Multicompartment Body Model"

<1. Draw a natural log plasma concentration versus time profile for a drug administered by the intravenous bolus route and best characterized by a two compartment model.

1-a The slope of the terminal phase of the above plot equals ________________.

1-b The intercept of the terminal portion on the ln plasma concentration axis is termed __________.

1-c Beta (b) is the terminal __________constant of the drug as it leaves the body.

1-d One way to calculate a distribution rate is to use the method of ____________________.

1-e the first step in the method of residuals is to ________ the terminal straight-line portion of the curve.

1-f The extrapolated points are subtracted from the actual _______________ observed at the corresponding times.

1-g The slope of the residual line equals ___________________.

1-h "A" is the __________ of the ln plasma concentration axis by the __________________ line.

1-i The concept of residuals attempts to separate the two processes of ____________.

2. A 250 mg I.V. dose of amoxicillin was administered to a healthy, 70-kg 28-year-old male. The disposition following administration was described by the equation:

Explain in your own words why the values for Vdc and Vdss differ (no equations).

3. Explain, why there are differences in Vc and Vdss in a two compartment body model.

4. Pharmacokinetic models are used to describe plasma-concentration time profiles after defined forms of administration. Select from the following list (a-g) the correct model for each of the profiles (1-5) shown below.

a. 2 compartment body model, constant infusion

b. 1 compartment body model, constant infusion

e. oral absorption (1 tablet) plus i.v. injection

f. pulmonary inhalation (1 puff from a metered dose inhaler)

g. none of the above

 1) Model:___ 2) Model:___ 3) Model:___ 4) Model:__ 5) Model:_____

5. Mark whether the following statements are true or false.

drugs do not show linear pharmacokinetics, when plasma level time profiles (log C- time) are not linear.

K10 does not depend on K12 or K21

the larger the difference between Vc and Vdarea the more difficult is the design of an optimal loading dose for constant infusion.

the larger the difference between Vc and Vdss, the more drug is in the peripheral compartment during the b-phase.

if Vc=Vdss, the plot of log c versus t is a straight line.