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PHA 5127
Answers Case Study 5
Fall 2007
Set I:
True or False
T F 1: A one compartment model means that drug in the blood is in rapid equilibration
with drug in extravascular tissues. (T)
T F 2: For a linear model, the rate constant for elimination is not proportional to the
amount of drug remaining to be eliminated. (T)
T F 3: Clearance and volume of distribution are independent each other, but both of
them are dependent of dose. (F)
T F 4: A drug with a linear protein binding has linear pharmacokinetics. (F)
can have nonlinear elimination
T F 5: In a linear one-compartmental model, lower dose and lower volume of
distribution result in a lower initial drug concentration after a single IV bolus. (F)
C(0)=Dose/Vd
T F 6: In a linear one-compartmental model, any two concentration points in
concentration-time profile can determine drug half-life after a single IV bolus. (T)
2
1
2 1 1 / 2
ln
C
C
t t t
T F 7: Total clearance is always greater or equal to renal clearance. (T)
CLtot = CLren + CLbil + CLmet
Set II:
Jane, 5’8”, 35-year-old, is being treated with the new drug for an infection disease. Jane weights
64.4 kg. Cpcreat in Jane is 0.8 mg/dL Assume a Vd of 0.24 L/kg*(TBW), and clearance of this
drug is equal to creatinine clearance, and this drug follows a linear one compartment model.
- In order to achieve initial concentration 6 mg/L, please calculate this IV bolus dose.
Vd = 0.24 L/kg
x kg L kg
L
V (^) d 64. 4 15. 5
Initial Cp = 6 mg/L
To determine the correct dose, we may use: V d
Dose
Cp 0 = Æ D = Cp 0 ⋅ Vd
D = (6mg/L)(15.5 L) = 93 mg
- Calculate half-life of this drug, and how many half-lives will it take to drop concentration
from 6 mg/L to 750 μg/mL
IBW= 45.5 kg + 2.3 kg for each inch over 5 ft in height
=45.5+2.3*8=63.9 (kg) Æ TBW<1.2 IBW
ml L hr Cp
age weight CL female creat
creat^99.^44 /min^5.^97 / 85 0. 8
1
- 97 / 15. 5 0. 385
− = = = hr Vd
Cl k e
hr k
t e
6 mg/L Æ 3mg/L Æ 1.5mg/L Æ 0.75mg/L=750 μg/mL (3 half-lives)
OR:
Assume 6mg/L is initial concentration:
0.75mg/L=6mg/LEXP(-0.385t) Æ t=5.4 hr Æ 5.4/1.8=3 half-lives
SET IV:
The renal clearances, the fractions of unbound in plasma and the molecular weights of four drugs
in a 75 kg subject are as follows:
CLrenal (mL/min) fu MW
A 20 0.5 500
B 0.10 0.5 200
C 20 0.1 800
D 50 0.9 100
Which of following statement is true? (GFR is 130 mL/min and urine flow is 1.5mL/min.)
A: Drug A has renal secretion.
B: Drug B has renal secretion.
C: Drug C has renal secretion.
D: Drug D has renal secretion.
E: None of above
Answer: C
Filtration Secretion Reabsorption
A (^) √
MW<
B √
MW<
C √
MW<
D √
MW<
