Transcript Document

Dosing Regimen Concepts
Applications
Practice Problems
Discussion
True or False ?
Accumulation always occurs.
Time to reach the plateau
depends on the frequency of
drug administration.
The extent of accumulation
increases when the drug is
given less frequently.
At plateau, the amount of drug lost
within a dosing interval equals the
oral maintenance dose.
True or False ?
The larger V, the smaller Css,av
Css,av depends on the
absorption kinetics of the
drug.
The faster drug is
administered, the shorter the
time to steady state.
AUC0- after a single dose is equal
to AUC at steady state.
During an infusion at steady state, rate in equals
a. rate out
b. rate out
c. rate out
d. rate out
e. all of the above
If the plasma concentration of a drug is measured
after its infusion to steady state, the clearance value is
calculated from
a. Dose/AUC
b. KEV
c. Ko / Css
d. (ln 2) V / t1/2
e. any of the above
Amikacin
Cyclophosphamide
Dexamethasone
CL [L/h]
5.5
5.5
16
V [L]
19
56
56
If the above drugs were administered by infusion at the
same rate until steady state
a. Amikacin and Cyclophosphamide would have the same Cp,ss.
b. Amikacin and Dexamethasone would have the same Cp,ss.
c.
Cyclophosphamide and Dexamethasone would have the
same Cp,ss.
d. they would all have a different Cp,ss.
e. none of the above.
Amikacin
Cyclophosphamide
Dexamethasone
CL [L/h]
5.5
5.5
16
V [L]
19
56
56
If the above drugs were administered by infusion at the
same rate until steady state
a. Amikacin and Cyclophosphamide would have the same Ass.
b. Amikacin and Dexamethasone would have the same Ass.
c.
Cyclophosphamide and Dexamethasone would have the
same Ass.
d. they would all have a different Ass.
e. none of the above.
Which of the following is not a determinant of the
steady-state concentration?
a. V
b. CL
c. t1/2
d. Ko
e. none of the above
Which of the following pharmacokinetic parameters can
be calculated if plasma concentration-time data are
available during infusion (Ko known) to steady state ?
a. V
b. CL
c. KE
d. t1/2
e. all of the above
The following five drugs were all administered at the
same rate of infusion, Ko. Fill in the missing values in
the Table below.
Drug
CL
V
t90%ss
Css
Ass
[L/h]
[L]
[h]
[mg/L]
[mg]
A
20
50
B
20
100
C
20
25
D
40
50
E
10
50
10
Drugs A and B have the following CL (L/h) values; if
both drugs were infused at the same rate, Ko
CL
V
A
5
50
B
10
50
a. A would reach steady state faster than would B.
b. A would have a higher steady state plasma
concentration than would B.
c. B would have a higher steady state body level than
would A.
d. B should have a loading dose administered; A
should not.
e. A should be formulated in a sustained release
preparation if it were to be given orally.
Ceftriaxone t1/2 = 7.3 h and V = 11.5 L
If an i.v. infusion of 100 mg/h has been running for 5.5
h, what would be the Cp ?
Ceftriaxone t1/2 = 7.3 h and V = 11.5 L
What will be the value of Cp,ss ?
How much more time will pass (t = 5.5 h now) before
90% of Cp,ss is achieved ?
Ceftriaxone t1/2 = 7.3 h and V = 11.5 L
If at t = 5.5 h into the infusion we want to go
immediately to steady state, how much ceftriaxone
should be administered immediately ?