CHAPTER 7
Oral Dosing
Author: Michael Makoid
Reviewer: Phillip Vuchetich
OBJECTIVES
After successfully completing this chapter, the student shall be able to
1.
Given patient drug concentration and/or amount vs. Time profiles, the student will
calculate (III) the relevant pharmacokinetic parameters ( Vd , K, km , k r , ka , AUC ,
Clearance, MRT, MAT) available from oral data.
2.
You should be able to determine the K from the terminal portion of the curve.
3.
You should be able to determine the ka from either the curve stripping Moment
techniques.
4.
You should be able to calculate the Absolute Bioavailability from comparing IV
and oral (or some other process which involves absorption) data.
5.
You should be able to calculate the Comparative Bioavailability from comparing
the generic to the inovator product.
6.
You should be able to qualitatively evaluate bioequivalence as determined by rate
of absorption (peak time) and extent of absorption (Area Under the Curve - AUC,
and ( C p ) max ).
7.
You should be able to evaluate bioequivalence data.
8.
You should be able to lucidly discuss bioequivalence and recommend to another
competant professional if you believe products to be equivalent.
9.
You should be able to properly use vocabulary relative to bioequivalence.
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7.1 Oral dosing
7.1.1
VALID EQUATIONS: ( ORAL DOSING, PLASMA)
where
CB
ka
–k a t
fD
– Kt
C p = ------ ⋅ --------------- ⋅ ( e – e )
Vd ka – K
(EQ 1-38)
AUC ( oral ) ⁄ Dose ( oral )
f = -------------------------------------------------------------AUC ( iv ) ⁄ Dose ( iv )
(EQ 1-39)
AUC ( generic ) ⁄ Dose ( generic )
CB = -------------------------------------------------------------------------------------AUC ( inovator ) ⁄ Dose ( inovator )
(EQ 1-40)
ka
ln ----K
t p = ----------k
----aK
(EQ 1-41)
Xa
------ = K ⋅ AUC ∞ – ( C p + K ⋅ AUC t )
v
(EQ 1-42)
= the comparative bioavailability
f = the absolute bioavailabilty; the fraction of dose which ultimately reaches systemic circulation (which is made up of the fraction of the dose which is absorbed
times the fraction which gets past the liver (first pass effect))
ka
7.1.2
= absorption rate constant.
UTILIZATION
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Oral Dosing
Ampicillin
(Problem 57)
The following information is available for ampicillin: 90% is excreted unchanged and a 250 mg IV bolus dose yields an
AUC of 11 mic/mL*hr. The following blood level profile has been reported for two brands of ampicillin which were
given as 500 mg oral capsules.
TABLE 1-3.
Time (hr)
µg
MEAN SERUM LEVEL -------mL
LEDERLE
BRISTOL
0.5
0.37
0.38
1.0
1.97
1.91
1.5
2.83
2.49
2.0
3.15
3.11
3.0
2.73
2.79
4.0
1.86
1.95
6.0
0.43
0.49
Find the following:.
a.
k for both products.
b.
k a for both products.
c.
k u for both products.
d.
AUC for both products.
e.
f for both products.
f.
t max for both products.
g.
Cl
h.
Vd
i
Cp 0 for a 250 mg IV dose.
j.
Cp max
k.
Are these two products bioequivalent? Why or why not?
l.
What infusion rate would be necessary to maintain a serum
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Oral Dosing
plasma concentration of 2mcg/mL
The data was plotted as above with the best fit line drawn. From the graph the following parameters were derived:
TABLE 1-4. Comparison
of Ampicillin
Lederle
Bristol
–1
K ( hr )
0.688
0.635
Ratio (L/B)
K a ( hr )
–1
0.858
0.831
T max ( hr )
1.74
1.8
0.97
( C p ) max ( µg ⁄ mL )
3
2.9
1.03
AUC (trapaziodal)
11.4
11.6
0.98
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2) In a clinical study (DiSanto & DeSante, JPS 64:100,1975) prednisone was
administered to 22 adult healthy volunteres (average weight 64.5 kg) either as one
50 mg tablet (product A) or as ten 5 mg tablets (product B). The following data
was observed:
Time (hours)
Concentration (mic/100ml plasma)
A
B
0.5
40.8
57.3
1
70.0
77.1
2
79.5
82.3
3
80.7
69.4
4
68.6
60.6
6
49.4
48.0
8
35.0
33.7
12
15.3
17.4
24
2.1
3.0
Find ka’s for both products.
Calculate peak time and Cp max and AUC for both products.
Can you conclude that these products are bioequivalent ?
(Reasons should include discussion of rate and extent of absorption)
Answer:
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Product A
Ka (hr^-1)
1.19
Tmax (hr)
Product B
Ratio (A/B)
1.8
2
1.52
1.31
Cmax (mcg/100mL)83.2
82.8
1.00
AUC (trapazoidal)676.52
688.81
0.976
Can you conclude that these products are bioequivalent ?
No, Time to peak (Tmax) is outside guidelines.
3) Wilkenstein et al.(Gastroenterology 74:360,1978) tested 12 normal healthy
volunteers in a four way crossover design of four dosage forms containing 300 mg
of cimetadine. The following data was obtained:
A.U.C. (mic/ml x hr)------
A
B
5.2
5.4
C
D
% recovered in urine intact77.177.147.149.0
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Oral Dosing
Peak serum conc.(mic/ml)------ 1.53 1.44
Onset (hr)
0
Duration (hr)
4.5
Time to peak (hr)0
0.34
0.65
4.0
4.2
4.4
1.0
2.0
A = IV bolus B = IM inj. C = Oral Liq. D = Oral Tab.
The plasma concentration - time profile for product A is as follows:
time(hrs)
(ug/ml)
time(hrs)
(ug/ml)
1
1.79
6
0.45
2
1.36
12
0.08
4
0.78
a} Using linear regression, find K & Cp0.
b} What is the absolute bioavailability (f) of the liquid.
c} How does that correlate with % recovered intact in the urine?
d} Would you consider the oral forms bioequivalent?
Why/Why not?
f} What infusion rate would you suggest to maintain a plasma concentration of
0.75 mic/ml ?
g} How long would it take that infusion rate to attain a therapeutic plasma concentration of 0.5 mic/ml ?
Answer:
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Oral Dosing
IV Bolus Parameters:
Cp max2.4 mic/mL
AUC 8.5
K
0.283 hr^-1
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a} Using linear regression, find K & Cp0. (graph)
b} What is the absolute bioavailability (f) of the liquid.
5/2/8.5 = 0.61
c} How does that correlate with % recovered intact in the urine?
Very well. Only 61% (f) of liquid gets in and you would expect only 77% of that to
show up in the urine because only 77% of the IV dose shows up in the urine
(.61*.77=.47).
d} Would you consider the oral forms bioequivalent? (No)
Why/Why not? Ratio of peak times ouside guidelines.
e} What infusion rate would you suggest to maintain a plasma concentration of
0.75 mic/ml ?
Q = Cpss * K * V = 0.75 mg/L * 0.283 hr^-1 * 125 L = 26.54 mg/hr
f} How long would it take that infusion to attain a therapeutic plasma concentration of 0.5 mic/ml ?
Cp = Q/(K*V)(1-exp(-K*T) = 0.5 = 26.54/(0.283*125)*(1-exp(-0.283*T)) --> 3.9
hr
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4) LYSERGIC ACID DIETHYLAMIDE (LSD) was given to human volunteers at
the dose of 150 mic orally. (Impregnated blotter dosage form.) The following
data was obtained:
Time
Cp (ng/ml)
Time
2.0
Cp (ng/ml)
0.25
1.75
4.6
0.5
2.9
3.0
4.1
0.75
3.7
4.0
3.3
1.0
4.2
6.0
2.1
1.5
4.6
8.0
1.4
a) Find ka
b) An IV dose of 100 mic resulted in an AUC of 20.4 ng/ml*hr. Find f.
c) The volunteers ability to concentrate as measured by their ability to do standard
tasks was also monitored. (100% control means no drug interference.) The following data was obtained:
Cp (ng/ml)
% Control
Cp (ng/ml)
5.5
33
1.5
65
4.1
40
1.1
80
2.9
52
% Control
If 100 mic dose were given by IV bolus, how long would it be before the volunteer
would regain 80% of his control?
Answwer:
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Oral Dosing
Evaluation of the graph of Concentration vs. time yields:
Cpmax
4.63 ng/mL
T max
1.7 hr
AUC (trap)30.07
K
0.225 hr^-1
m (-K)
-0.225 hr^-1
Ka
1.22 hr^-1
f (AUCoral/Doseoral)/(AUCiv/Doseiv) = .98
Evaluation of the graph of response vs ln(concentration) yields:
dR/dln(c) = 27.86
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Multiplying dR/dln(c) * dln(c)/dt (m of the previous graph) yields dR/dt = 27.86 *
-0.225 = 6.26%/hr
100 mic dose IV yields Cp0 of (Cp0 =AUC * K = 20.4 * 0.225) 4.59ng/mL.
The response of a 100 mic dose is (R = 27.86*ln(4.59)+19.9) 62.3%
Response = Response at t=0 - dR/dt * t
20% = 62.3% - 6.26%/hr
T
=
* t hours
6.76 hours
5. The following data was collected from a double blind cross over study between
500 mg dose of cloxacillin made by Bristol (Tegopen@) and a generic product
which you might want to put in your store.
Time
(Conc. mic/ml)
Time
TEGOPEN GENERIC
(Conc. mic/ml)
TEGOPEN GENERIC
0.25
.41
0.1
1.5
6.93
7.75
0.5
8.56
6.39
2
4.95
5.16
0.75
11.97
11.44
1
11.28
11.42
9.57
9.64
1.25
3
4
2.19
1.48
2.29
1.30
Calculate the comparative bioavailability.
Would you consider these products bioequivalent? Why/Why not?
Answer:
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Oral Dosing
Evaluation of the above graphs yields:
Tegopen
Cpmax (mic/mL)10.8
GenericRatio (G/T)
9.94
0.92
T max (hr)
0.74
0.89
1.20
AUC (trap)
21.7
21.06
0.97
K (hr^-1)
0.72
0.8
ka (hr^-1)
4.3
2.69
Actual evaluation of ka and peak time is dificult because of the pucity of data at
early time points however all relavent parameters meet guidlines.
7. The F.D.A. reported the following data submitted to be consideration regarding
the equivalence of Mylan Pharmaceuticals’ Tetracycline with that of Lederle and
an intervenous bolus dose. (Dose 250 mg).
Time(hrs)
Conc.(mcg/ml) Time(hrs)
Lederle Mylan I.V.
Conc.(mcg/ml)
Lederle Mylan I.V.
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0.5
0.55
0.20 5.2
4
2.70
2.60 2.9
1
1.80
1.35 4.8
6
2.20
1.80 2.1
1.5
2.11
1.75 4.4
9
1.35
1.25 1.26
2
2.35
2.10 4.0
12
0.83
0.74 0.76
3
2.65
2.25 3.4
15
0.50
0.45 0.46
Would you consider Mylan to be bioequivalent to the Lederle product ?
Calculate the absolute bioavailability of Lederle Tetracycline.(.77)
f) Calculate the volume of distribution of tetracycline. (44.3 L)
g) Tetracycline has a pKa of 9.7. Tetracyclines tend to localize in the dentin and
enamel of developing teeth causing hypoplasia and permanent discoloration of
teeth. Would you recomend tetracyline for a 110 pound lactating mother ?
Support your argument with the dose of the child. (Child’s weight 11 lbs. and he
eats 2 oz of milk every 2 hours. Mom’s average plasma concentration is maintained at 3 mic/ml by taking 250 qid. pH of the milk is 6.1, pH of blood is 7.4)
Answer:
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Oral Dosing
Pharmacokinetic parameters:
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Oral Dosing
Lederle
Cpmax (mic/mL)2.75 2.42
Tmax (hr)
3.04
AUC
Mylan
IV
5.65
3.08
26.4
0
23.3
k (hr^-1)
0.165
0.161
Ka (hr^-1)
0.684
0.729
31.4
0.167
Ratio of bioequivalence parameters (Cpmax, Tmax and AUC) are all within guidelines. So, the would be considered bioequivalent.
Absolute bioavailability f (= (AUCoral/DOSEoral)/(AUCiv/DOSEiv) = (26.4/
250)/(31.4/250) is 0.84.
Volume of Distribution (Dose/Cp0 = 250 mg/ 5.65 mg/mL) is 44.2 L
The ratio of milk to blood is about 200.
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Oral Dosing
r(m/b) = (10^(pKa-pH) + 1)milk / (10^(pKa-pH) + 1)blood
= (10^(9.7-6.1)+1)/(10^(7.4-6.1)+1) = 10^3.6/10^1.3 = 10^2.3 = 200
Dose the kid gets is mom’s plasma concentration * Ratio(M/b) * volume of milk /
day = 3 mic/mL * 200 * 60cc * 12 feedings = 432 mg.day
Mom gets 1000 mg/day
Ratio of dose on a mg/kg basis (kid/mom) = (432/5)/1000/50) = 4.32 - Kid’s getting more than mom.
Fifty miligrams of ketameperidine was given by IV bolus. The following urinary
profile was obtained for the only metabolite N-methyl-ketameperidine:
Collection period (hr)
Mean urinary excretion rate (mg/hr)
0.0 - 0.5
2.26
0.5 - 1.5
5.83
1.5 - 2.5
5.43
2.5 - 3.5
4.60
3.5 - 5.0
2.36
5.0 - 7.0
1.47
7.0 -10.0
0.96
10.0 -18.0
0.44
Calculate K, km and ku.
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What Percent of ketameperidine was metabolized?
Answer:
With only one data point in the early time points, the larger rate constant is in ques-
tion. The terminal slope is assumed to be K. The AUC will yield the amount of
ketameperidine which was metabolized (dXmu/dt * t = Xmu).
K (hours^-1) 0.216
AUC (mg)30.3
30.3 mg showed up as metabolite = 60.6% of 50 mg dose.
km = 60.6% * K = 0.131 hours^-1
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kr = K - km = 0.085 hours^-1
Aminophylline consists of THEOPHYLLINE (85% W/W) & Ethylene diamine
(15% W/W)
THEOPHYLLINE is the active compound measured in blood.
THEOPHYLLINE has a volume of distribution of 0.45 l/kg.
THEOPHYLLINE is 10% excreted unchanged and 90% metabolized to inactive
metabolites.
THEOPHYLLINE has a therapeutic range between 20 and 10 mg/l.
AUC FROM 0 to infinity for THEOPHYLLINE (given as 400 mg AMINPHYLLINE) is 120 mg/l x hr.
The average plasma concentration of THEOPHYLLINE given as 400 mg of AMINOPHYLLINE is as follows:
time
conc. time
conc.
(hrs)
(mg/L) (hrs)
(mg/L)
0.5
7.24
4.0
8.06
1.0
9.56
6.0
6.89
2.0
10.00
8.0
5.57
3.0
8.84
10.0
4.53
Find f, K, ka, Vd,total body clearance.
Find the infusion rate necessary to maintain a plasma concentration of 15 mg/l.
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Answer:
AUC (mg/L)*hr117.8
K (hr^-1)
0.096
ka (hr^-1)
2.11
f = (AUCoral/DOSEoral)/(AUCiv/DOSEiv) =
= (117.8 / 400
)/(120 / 400 ) = 0.98
Vd
AUC * K = Cp0iv
120 * 0.096 = 11.52 mg/L
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Vd = Dose/Cp0 = (400mg*0.85)/11.52 = 29.5 L
TBC = K * Vd = 0.096/hr * 26.5L = 2.83 L/hr
Infusion rate = Q = Cpss * TBC = 15 mg/L * 2.83 L/hr = 42.45 mg/hr Theophylline = 42.45/.85 = 50 mg/hr Aminophylline
Abbott labs has provided the following data conserning their ORETIC tablets
(hydrochlorthiazide tablets U.S.P.) Dose given was 50 mg.
time
conc. time
conc.
(hrs)
(mg/L) (hrs)
(mg/L)
0.5
0.05
3.0
0.31
1.0
0.21
4.5
0.23
1.5
0.27
6.0
0.18
2.0
0.31
8.0
0.12
a Find K, ka, Cmax,
Answer:
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The data is plotted both without (first figure) and with (second figure) a lag-time
which is associated with the release of the drug from the delivery system. Note
that the addition of the lag-time improves the fit.
The parameters obtained from each fit are:
WithoutWith
Cpmax (mg/L)0.22
0.31
Tmax (hr)
2.28
3.45
AUC (mg/L*hr)2.2
2.26
K (hr^-1)
0.216
0.201
ka (hr^-1)
0.380
1.10
t lag (hr)
0.0
0.393
It takes the tablet about 20 minutes to release the drug!
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Wilkenstein et al.(Gastroenterology 74:360,1978) tested 12 normal healthy volunteers in a four way crossover design of four dosage forms containing 300 mg of
cimetadine. The following data was obtained:
A
B
C
D
AUC(mic/ml x hr)
---
recovered in urine intact77.177.1
---
5.2
54.9
55.8
Peak serum conc.(mic/ml)--- --Onset (hr)
0
Duration (hr)
4.5
Time to peak (hr)
1.53
1.44
4.6
0
5.4
0.34
0.65
4.2
4.4
1.0
2.0
A = IV Bolus B=IM injection C = Oral liquid D= Oral tablet
The plasma concentration vs. time profile for product A is as follows:
time (hrs)
conc.(ug/ml)
1
1.79
2
1.36
4
0.78
6
0.45
12
0.08
a} find K, Cp0.
Both can be found from the graph. K = .283/hr Cp0 = 2.36 mic/ml
b} What is the absolute bioavailability (f) of the liquid.
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5.2/8.5 = 0.61
c} How does that correlate with % recovered intact in the urine?
Very well. Only 61% (f) of liquid gets in and you would expect only 77% of that
to show up in the urine
because only 77% of the IV dose shows up in the urine
(0.61 * .77 = .47).
d} How can you explain the variation in % recovered intact in the urine?
e} Would you consider the oral forms bioequivalent ? Why/Why not?
No. The ratio of peak times is outside the guidelines.
f} What infusion rate would you suggest to maintain a plasma concentration of
0.75 mic/ml?
Q = Cpss * K * V = 0.75 mg/L * 0.283/hr * 125L = 26.54 mg/hr
g} How long would it take that infusion rate to attain a therapeutic plasma concentration of 0.5 mic/ml ?
Cp = Q/(K * V)(1-exp(-K*T) = 0.5 = 26.54/(0.283 *125)*(1-exp(-0.283 * T)) > 3.9 hr
Roxane labs of Columbus, Ohio offers the following data for your review of their
Quinidine Sulfate tablets (Dose 200 mg). It is compared against the reference
standard by Ely Lilly and company at the same dose.
Time (hours)Concentration (mcg/ml)
Roxane
Lilly
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Oral Dosing
1
.42
.58
2
.73
.77
3
.71
.74
4
.61
.66
6
.45
.52
8
.32
.34
12
.20
.22
a) Calculate the comparative bioavailability.
b) Would you consider Roxane Quinidine Sulfate to be bioequivalent to the Lilly
product ?
Answers
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Roxane labsEli Lilly
w/o
w
w/o
w
Rw/o(R/L)Rw(R/L)
Cpmax (mcg/mL)0.650.740.740.76 0.88
0.97
AUC (mcg/mL*hr)6.086.236.756.84 0.90
0.91
Tmax (hr)
2.69
2.05
2.33
2.10
T lag (hr)
0.0
0.70
0.0
0.36
1.15
0.98
Yes. Ratios are within guidelines.
Shand et al. offers the following data for propranolol :
Answers:
Time Concentration (ng/ml)
(hours) 10 mg I.V. 80 mg oral
0.5
--
50
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1
--
77
1.5
--
100
2
29
100
3
24
90
4
18
78
5
15
59
6
11
45
7
9
32
a) find ka
b) Calculate the absolute bioavailability of propranolol.
c) Calculate TBC
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IV data
Oral Data
w/o
w
AUC (ng/mL*hr)201.3562.8 540
Cpmax (ng/mL) 47.7 97.8
99.7
Tmax (hr)
0
2.0
K (hr^-1)
0.239
0.324 0.421
ka (hr^-1)
---
0.715 0.548
2.1
T lag
0.0
0.02
Absolute bioabailability = (AUCoral/DOSEoral)/(AUCiv/DOSEiv)
= (562.8/80)
(540 / 80)
/(201.3/10) = 0.35 or using lag time data
/(210.3/10) = 0.335
TBC = Dose / AUC = 10,000 mic/ 201.3 mic/L*hr
= 50 L/hr or
0.35*80,000mic /562.8 mic/L*hr = 50 L/hr
Niazi et al. offers the following data for meperadine :
Meperidine : is 95% metabolized
has an absolute bioavailability of 0.4
has a hepatic plasma extraction ratio of 0.6
has a volume of distribution of 100 L.
has a half life of 3.5 hours.
a) Calculate TBC
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TBC = K * V = (0.198/hr)(100L) = 19.8 L/hr
b) Calculate the intrinsic hepatic plasma clearance of meperidine.
19.8 L/hr * .95 = 18.8 L/hr
c) Calculate the effect on total body clearance in a patient with viral hepititis (FI =
0.3).
Clh*/Clh = (.3)(1)/1 + .6(.3 - 1) = .3/.58 = .517
(.517)(18.8) = 9.72
TBC = 1 + 9.72 = 10.72
d) Calculate the effect on total body clearance in a patient with stenosis (FR = 0.3).
Clr*/Clr = (1)(.3)/.3 + .6(1 - .3) = .3/.72 = .417
TBC = 18.8 + .417 = 19.22
e) Comment on which patient might need modification in therapy and why.
The patient with viral hepatitis would need modification in therapy. Because
of the decrease in TBC, we
can see that the drug is staying the body much
longer than normal, therefore the dosage regimen should
be decreased.
Chlorthalidone is used to treat high blood pressure. The following information is
offered regarding a generic
and a brand name chlorthalidone 50 mg tablet:
Time Conc. (mcg/ml)
(hours)
Hygroton@Generic
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.5
0.14
0.15
1
0.51
0.64
2
1.23
1.67
3
1.94
2.48
4
2.20
2.91
6
2.64
3.49
8
2.86
3.52
12
3.43
3.82
24
3.22
3.38
48
2.45
2.74
72
1.53
1.91
96
1.20
1.40
120
0.76
0.77
Pharmacokinetic parameters
Cpmax (mg) 3.73
4.62
Time to peak (hr) 13.810.8
AUC (0 to Inf)293
336
Xu inf (mg)18.3
22.1
Ka (hr^-1)0.168
0.253
Ke (hr^-1)0.019
0.019
Average mean83.1
84.5
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blood presure
a) Calculate the comparative bioavailability.
(336/50mg)/(293/50mg) = 1.15
b) Would you consider the generic product to be bioequivalent to the USV
(Hygroton@) product? Prepare a short statement that you would tell a patient
regarding why you would or would not make a generic substitution for this drug.
No. The maximum concentration the generic is too much greater than that of
the brand name product.
They are not considered to be bioequivalent.
R(G/H)
Cpmax (mg) 1.23
outside
Time to peak (hr)0.78outside
AUC (0 to inf)115
ok
Buspirone is a new anxiolytic agent that has been found to be effective for the
treatment of generalized anxiety disorder at a mean dose of approximately 20 mg/
day orally in divided doses. Buspirone is metabolized almost entirely. Less than
0.1% is found intact in the urine. The following data has been presented by Gammans (Am J Med:80(supp 3b),41-51;1986):
Time (hours)Concentration (ng/ml)
(hours)
1 mg I.V.20 mg oral
0.25
--
1.07
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0.50
4.33
1.76
1.0
3.75
2.45
2
2.80
2.51
3
2.10
2.05
4
1.57
1.60
6
0.8
0.91
a) find ka
b) Find Oral Peak Time and Oral Cmax.
c) Calculate the absolute bioavailability of buspirone.
answer:
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Oral Dosing
IV
Oral
Cpmax (ng/mL) 5.0 2.6
AUC (0 to inf)17.4
13.9
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Tmax (hr)
0
K (hr^-1)
0.290 0.289
ka (hr^-1)
1.5
1.3
Absolute bioavailability, f, = (AUCoral/DOSEoral)/(AUCiv/DOSEiv)
= ( 13.9 / 20)
/( 17.4/ 1
)
= 0.04
Valproate is a carboxylic acid anticonvulsant. Its activity may be related, at least
in part, to increase concentrations of the neurotransmitter inhibitor gamma aminobutyric acid in the brain. It is used alone or in combination with other anticonvulsants. in the prophylactic management of petit mal. It appears to be almost
entirely cleared by liver function with negligible amounts excreted into the urine
unchanged. It comes as soft gelatin capsules of 250 mg and enteric coated tablets
250 and 500 mg as well as oral syrup of 250 mg / 5 cc. Two different formulations of Valproate (250 mg) were prepared by Abbott and compared. The data is
as follows:
Time(Hr.)Formulation BFormulation A
0.5
3.4
AUC = 287 mg/L * hr
1.0
6.0
Ka = 0.7 hr^-1
1.5
7.9
Ke = 0.065 hr^-1
2.0
9.3
2.5
10.3
3.0
10.9
4.0
11.6
6.0
11.4
8.0
10.5
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12.0
8.3
18.0
5.7
24.0
3.8
1) find ka for formulation B.
2) Five hundred mg of valproate was administered by IV bolus. The AUC for that
route was 574 mg/L * hr. Calculate f for formulation A. Calculate Cp0 for the IV
dose.
3) Find Peak Time and Cmax for formulation A.
4) Calculate the comparative bioavailability of formulation B.
5) Would you consider formulation B to be bioequivalent to Formulation A ? Prepare a short statement in which you would substantiate that stand that you might
need to respond to another health professional who asked you to stock that formulation for his patients.
6) Calculate the Total Body Clearance (TBC) of valproate.
Answers:
Formulation B
R(A/B)
AUC = 243.3 mg/L * hr 1.18
Cpmax = 11.7 mg/L1.12
Tp max = 4.70 hr0.79
ka
= 0.493 hr^-1
K
= 0.0655
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Tmax(A) = ln(ka/K)/(ka-K)= 3.75 hr
cpmax =
(ka/(ka-k))*(fX0/Vd)*(exp(-k*tmax)-exp(-ka*tmax)
13.3 mg/L
Absolute bioavailability, f,=(AUCoral/DOSEoral)/(AUCiv/DOSEiv)
= (287/250)/(574/500)
= 1.0
Comparative bioavailability =(AUCb/DOSEb)/(AUCa/DOSEa) = 243.3/287 =
0.85
TBC = Dose / AUC = 500 mg / 574 mg /L * hr
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The following data was made available by Lederle Labs regarding its generic
Procainamide HCl. (Dose 250mg).
Procainamide is a base (pka =9.1). As the hydrochloride salt it is 87% Procainamide.
Time (hrs)Conc.(mcg/ml) Procainamide Base
Lederle
Squibb
I.V.
0.33
0.68
0.26
0.5
0.82
0.67
0.66
1.17
0.93
1
1.23
1.12
1.45
1.33
1.31
1.19
1.35
2
1.39
1.12
1.18
3
0.93
0.96
0.95
4
0.74
0.74
0.77
6
0.51
0.51
0.51
8
0.32
0.30
0.33
12
0.11
0.09
0.14
a) find ka of the Squibb product
b) ka of the Lederle product.
c) Calculate the comparative bioavailability.
d) Would you consider Lederle to be bioequivalent to the Squibb product ?
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e) Calculate the absolute bioavailability of Lederle Procainamide.
f) Calculate the volume of distribution of procainamide.
g) Would you recommend your patient breast feed her newborn? Prepare a short
consult for her physician. Support your argument with the dose of the child.
(Child’s weight 11 lbs. and he eats 2 oz of milk every 2 hours. Mom’s average
plasma concentration is maintained at 4 mic/ml from a 1 g dose ever 6 hours. pH of
the milk is 6.3, pH of blood is 7.4)
Procainamide is cleared about 60% by liver and 40% by kidney function. 20 % of
cardiac output (70 ml/min/kg) goes to liver, 25% goes to the kidney. Mom’s
weight is 130 lb. Assuming her plasma vs time profile to be similar to the Lederle
product (i.e. pharmacokinetic parameters obtained from this information can be
used):
h) Calculate Total body clearance
i) Calculate the intrinsic hepatic plasma clearance of procainamide.
j) Calculate the effect on her total body clearance if she were to contract viral hepatitis which effect liver function (FI = 0.4). Prepare a short consult for her physician as to whether you would recommend a change in therapy. d) Calculate the
effect on her total body clearance stenosis of the liver (FR = 0.4). Prepare a short
consult for her physician as to whether you would recommend a change in therapy.
Answers:
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IV
LederleSquibb R(L/S)
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AUC (0 to inf)8.577.46.8
1.09
Cpmax
1.8
1.28
1.25
1.02
Tmax
0
1.43
1.45
0.99
K
0.212 0.247 0.256
ka
---
1.51
1.93
t lag
0
0
0.24
Absolute bioavailability, f,=(AUCoral/DOSEoral)/(AUCiv/DOSEiv)
= 7.4
/ 8.57
= 0.86
Vd = Dose/Cp0 = 0.87*250mg/1.8mg/L= 120.8 L
Ratio of milk to blood = (10^(9.1-6.3)+1)/(10^(9.1-7.4)+1)= 12.4
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Kid’s dose = 4 mic/mL * 12.4 * 60 mL/feeding * 12 feedings/day * 1 mg/1000 mic
= 36 mg/day
Ratio of kid’s daily dose/# to Mother’s daily dose/# = (36mg/11#)/(1000mg*4/
130#) = 0.42. The kid gets about half of the mother’s dose!
Nifedipine (Procardia @) is a calcium channel blocker which specifically inhibits
potential-dependent channels not receptor-operated channels, preventing calcium
influx of cardiac and vascular smooth muscle (coronary, cerebral). Calcium
channel blockers reduce myocardial contractility and A-V node conduction by
reducing the slow inward calcium current. They are indicated in angina, cardiac
dysrhythmias, and hypertension among others. Nifedipine appears to be metabolized entirely into an inactive metabolite, an acid and subsequently further metabolized to a lactone. Both the acid and the lactone are excreted into the urine and
the feces.
Echizen and Eichelbaum (Clin Pkin 1986; 11:425-49) and Kleinbloesem et al
(Clin Pcol Therap 1986; 40: 21-8) Reviewed the pharmacokinetics of Nifedipine.
While the drug is not routinely given by IV bolus and does not strictly conform to
a one compartment model, lets treat the data as if those problems can be ignored.
The following data is offered for evaluation:
25mg IV
10 mg oral tablet
Formula AFormula B
Time Cp
Cp
Cp
(hr.)
(mic/l)
(mic/l)
0.5
29.3
33.1
1
42.1
43.7
1.5
45.7
43.7
44.4
39.8
36.2
25.5
2
(mic/l)
139
3
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4
65.6
27
20.7
6
31.1
13.6
9.9
8
14.6
6.5
4.7
1.5
1.0
12
a} Find ka’s of the two products.
b} Calculate peak time and Cp max for both products.
d} Can you conclude that these products are bioequivalent ? (you must support you
argument)
e) Calculate the absolute bioavailability of product A.
f} What infusion rate would you suggest to maintain a plasma concentration of 30
mic/L ?
Answers:
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IV
A
B
R(A/B)
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Cpmax (mic/L)294.25 45.7 44.01.04
Tmax (hr) 0
1.57
1.18 1.33
AUC(0 to inf)785219.7182.7 1.20
ka (hr^-1)---
1.0
1.6
K (hr^-1) 0.375 0.374 0.375
No,Tmax is outside the guidelines.
Absolute bioavailability, f,=(AUCoral/DOSEoral)/(AUCiv/DOSEiv)
=(219.7/10)/(785/25)
=0.7
Q = Cpss * K * V = 0.955 mg/hr
Tetracycline HCl has a pKa of 9.7. Tetracyclines tend to localize in the dentin and
enamel of developing teeth causing hypoplasia and permanent discoloration of
teeth. Would you recommend tetracycline for a lactating mother ? Support your
argument with the dose of the child. (Child’s weight 11 lbs. and he eats 2 oz of
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milk every 2 hours. Mom’s average plasma concentration is maintained at 4 mic/
ml she is taking 250 mg T.I.D. ( Milk pH = 6.1, Blood pH = 7.4)
Tm/Tb = 109.7 - 6.1/109.7 - 7.4 = 20/1
The concentrarion of tetracycline in the mother’s milk is 80 mic/ml
The child takes in 720 ml of milk per day
80 mic/ml * 720 ml = 57600 mic = 57.6 mg
57.6mg/5kg = 11.52mg/kg = dose that the child is getting from the mother’s
milk.
I would not recomend tetracycline for a lactating mother. The dose that a nursing child gets from the milk
too high.
Oxazepam (acid, pKa 11.5) is an anxyolytic sedative with the usual adult dose 10
mg 3 times daily. If the circulating plasma concentration of oxazapam were 20
mic/ml for nursing 120 lb mother, would her 9 lb infant be getting a comparable
mg per kg daily dose if he consumes 2 oz of his mothers milk every 2 hours. Prepare a short consult for her physician in which you might (or might not) recommend the patient stop breast feeding while she is on this medication. Include
appropriate calculations.
Om/Ob = 1011.5 - 6.1/1011.5 - 7.4 = 20/1
The concentration of the mother’s milk would then be 400 mic/ml
400 mic/ml * 720 ml = 288000 mic given to baby = 288mg
288mg / 4.1kg = 70 mg/kg = dose/kg given to baby
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This dose is much greater then that given to the mother. The mother should
discontinue breast feeding
while taking Oxazepam.
Bioequivalence studies are sometimes done within the same company to check if
the tablets of the same drug, but different strengths (with the strength normalized)
could be considered equivalent (i.e. could two 5 mg tablets be considered equal to
one 10 mg tablet). While not strictly kosher (products are not pharmaceutical
equivalents because of different strengths), it is done. Here is the results of such a
study in which Zomax 100 and 200 mg tablets were compared. (Yes, I know that
Zomax was removed from the market after a short life of only 6 months.)
Zomax 100 mg tablet 200 mg tablet 50 mg IV bolus
Time Conc AUC
Conc AUC
Conc.
(hr)
(mg/L) (0->t)
(mg/L) (0->t)
(mg/L)
0.25
1.41
0.18
4.03
0.50
0.5
1.98
0.60
5.13
1.65
0.75
2.15
1.12
5.18
2.94
1
2.12
1.65
4.89
4.20
1.14
2
1.56
3.49
3.37
8.33
0.764
3
1.05
4.80
2.26
11.14
0.512
4
0.707 5.67
1.51
13.03
0.343
6
0.318 6.70
0.68
15.22
0.154
8
0.143 7.16
0.306 16.20
0.069
1) What is the elimination rate constant for zomax (hr) ?
A) 0.2
B) 0.3
*C) 0.4
D) 0.5
E) 0.6
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2) What is the volume of distribution of zomax given by IV bolus (L) ?
A) 43.85 B) 33.3 *C) 29.4 D) 25.9 E) 0.034
AUC = D/(Vd * K)
Vd = D/(AUC * K)
= 50mg/(4.25 * 0.4)
= 29.4 L
3) What is the volume of distribution of zomax given by 100 mg oral tablet ?
A) 43.85 *B) 33.3 C) 29.4 D) 25.9 E) 0.034
Vd = 100mg/(7.48 * 0.4)
= 33.4 L
4) What is the AUC(0->infinity_ for the IV bolus dose ?
A) 2.68 B) 2.85 C) 3.55 D) 4.08 *E) 4.25
5) What is the AUC(0->infinity) for the 100 mg tablet ?
A) 7.16 *B) 7.5
C) 16.20 D) 17
E) 37.38
6) What is the absolute bioavailability of the 100 mg tablet ?
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A) 0.84 *B) 0.88 C) 1
D) 1.14 E) 1.19
(7.48/100)/(4.25/50) = 0.88
7) What is the AUC(0->infinity) for the 200 mg tablet ?
A) 7.16 B) 7.5
C) 16.20 *D) 17
E) 73.98
8) What is the absolute bioavailability of the 200 mg tablet ?
A) 0.84 B) 0.88 *C) 1
D) 1.14 E) 1.19
(16.9/200)/(4.25/50) = 1
9) What is K * AUC (0->infinity) for the 100 mg tablet (mic/ml) ?
A) 2.9
*B) 3.0
C) 6.5
D) 6.8
E) 14.95
7.48 * 0.4 = 2.99
10) What is the absorption rate constant for the 100 mg tablet ?
A) 1.7
B) 2.2
*C) 2.6
D) 3.2
E) 3.7
11) What is the intercept of the extrapolated line for the 200 mg tablet ?
A) 3.5
B) 4.1
C) 5.6
D) 6.1
*E) 7.6
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12) What is the absorption rate constant for the 200 mg tablet ?
A) 1.7
B) 2.2
C) 2.6
D) 3.2
*E) 4.01
13) What is the Tmax for the 100 mg tablet ?
A) 0.5
B) 0.67 C) 0.75 *D) 0.85 E) 0.95
14) What is the Tmax for the 200 mg tablet ?
A) 0.5
*B) 0.67 C) 0.75 D) 0.85 E) 0.95
15) Would you consider these two tablets bioequivalent (given normalization for
dose) (consider all ratios to be the 100 mg / 200 mg parameter normalized as to
dose where applicable)?
A) Yes
B) No, because the ratio of the ka’s is 0.70
C) No, because the ratio of the AUCs is 0.44
D) No, because the ratio of the Cmaxs is 0.41
*E) No, because the ratio of the Tmaxs is 1.27
16) What infusion rate would you recommend to maintain an average plasma concentration of 1 mic/ml ?
A) 17.5 B) 13.3 *C) 11.8 D) 10.4 E) 9.0
Vd = D/Cp0 = 50mg/1.7mg/L = 29.4
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Q = Cpss * K * V = 1mg/L * 0.4/hr * 29.4L = 11.8
17) What would be the concentration (mg/L) 2 hrs after discontinuing the infusion assuming you reached steady state ?
A) 0.67 B) 0.55 *C) 0.45 D) 0.37 E) 0.30
Cpss = Cp0 * e-Kt
= 1mg/L * e(-0.4 * 2)
= 0.44
A 110 pound mother breast feeds her 11 pound infant while on morphine sulfate
(base, pKa = 9.85). Mother’s average circulating plasma levels are 0.5 ug/ml following a 10 mg IV dose q4h. (pH Milk = 6.1, pH blood = 7.4)
18) What is the Ratio of morphine concentration in the milk as compared to the
blood ?
A) 0.05 B) 0.5
C) 1
D) 2
*E) 20
Mm/Mb = 10(9.85 - 6.1)/10(9.85 - 7.4)
= 20
19) How much (mg) morphine is contained in 120 cc of breast milk (the child consumes 2 ounces every 2 hours) *A) 1.2 B) 0.12 C) 0.06 D) 0.03 E) 0.003
Mother’s blood conc. is 0.5mic/ml therefore her milk conc. is 10 mic/ml.
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10mg/L * 0.12L = 1.2 mg
20) In your professional judgment, will the child’s dose cause a problem ?
A) No, morphine does not concentrate in the milk and thus the milk is ok to drink.
B) No, the dose is too small. The ratio of the child’s dose to the mother’s dose is
0.12.
C) Yes, even though the dose is small, we don’t want any drug to get to the child.
*D) Yes, the dose is comparable to the mother’s dose. The ratio of the child’s to the
mother’s dose is 1.2.
E) Not my job. I only give what the doctor orders.
Answers:
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IV
Tablet Tablet
50 mg 100 mg200 mgR(100/200)
AUC(0 to inf)4.257.4816.9
0.89
Cpmax
1.7
2.15
5.23
0.82
Tmax
0
0.82
0.64
1.28
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K
0.4
0.4
-.4
ka
---
2.76
4.01
Tmax ratio is ouside guidelines.
Answers are rounded off. When you pick a foil, use that number in subsequent calculations when needed.
Rifampin (unionized free base pKa 7.9) is a drug used to treat TB. The following
data was collected following a 600 mg oral tablet from the inovator (Treatment A),
and a 600 mg oral tablet from a generic (treatment B), and a 400 mg IV dose
(Treatment C).
Concentration (mic/mL)AUC(0->t)
TreatmentA
B
C
0.5
5.3
4.8
1
10.3
8.6
B
Time (hours)
1.2
7.8
4.55
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1.5
10.2
9.8
9.15
2
9.4
9.8
2.5
8.9
9.2
3
7.5
8.4
4.7
4
5.9
6.7
3.7
6
3.6
4.1
2.2
8
2.2
2.5
1.3
10
1.3
1.5
0.8
12
0.8
0.92
0.5
6.1
14.05
18.8
AUC(0->inf)53.957.7
(mic/mL*hr)
Lag time (min)18.610.5
Cp max10.6
9.9
Ka (hr^-1)2.66
1) What is the Cp0 for C (mg/L)?
a) 0
b) 7.8
*c) 10
d) 12
e) 15
Cp0 = AUC * K
= 39.8 * 0.25
= 9.95
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2) What is the volume of distribution of Rifampin (L)?
d) 33.3 e) 26.7
a) 60
b) 51.3 *c) 40
Vd = D/Cp0
= 400mg/(9.95mg/L)
= 40.2 L
3) What is the half life for rifampin (hr)?
1.5
*a) 2.8
b) 2.3
c) 2.0
d) 1.75 e)
t1/2 = .693/0.25
= 2.77
4) What is the elimination rate constant for rifampin (hr^-1)? *a) 0.25 b) 0.3 c)
0.35 d) 0.4 e) 0.45
5) Calculate the AUC (0->1hr) for C (mic/mL*hr).
8.9 e) 17.8
a) 1.95 *b) 3.9
6) Calculate the AUC (12hr->inf.) for C (mic/mL*hr).
d) 1.25 e) 1.11
*a) 2
c) 7.8
b)
b) 1.67 c) 1.43
0.5/0.25 = 2
7) Calculate the AUC (0->inf) for C (mic/mL*hr).
40 e) 60
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a) 16
b) 26.85 c) 35
*d)
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8) Calculate the absolute bioavailability for the generic product.
0.95 c) 1
d) 1.05 e) 1.43
a) 0.70 *b)
(57.7/600)/(39.8/400) = 0.966
9) Calulate the comparative bioavailability for the generic product.
0.95 c) 1
*d) 1.05
a) 0.70 b)
e) 1.43
(57.7/600)/(53.9/600) = 1.07
10) Using Wagner-Nelson method, calculate the Ka for the generic product (hr^1). a) 0.45 b) 1 c) 1.55 d) 2 e) 2.45
11) Calculate the peak time for the generic product (min). a) 37 b) 67 c) 86 d)
91 e) 105
tp = [ln(Ka/K)]/(Ka - K)
= [ln(1.37/0.25)]/(1.37 - 0.25)
= 1.52 hr = 91 min
12) Calculate the peak time for the brand name product (min).
86 d) 95 e) 105
a) 37 *b) 59 c)
tp = [ln(2.66/0.25)]/(2.66 - 0.25)
= 0.98 hr = 59 min
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13) Are the two products bioequivalent?
a) yes, all federal requirements are met.
*b) no, the ratio of the peak times are out side federal requirements.
c) no, the ratio of the lag times are out side federal requirements.
d) no, the ratio of the Kas are out side federal requirements.
e) no, the ratio of the comparative bioavailabilities are out side federal requirements.
14) What is the ratio of the concentration of milk (pH 6.1) to blood (pH 7.4)? a)
0.05 b) 0.05 c) 1 d) 15.4 *e) 20
Rm/Rm = 10(7.9 - 6.1)/10(7.9 - 7.4)
= 20
15) The average plasma concentration for the mother (110#) is 2.5 mg/L from a
600 mg once a day dosing regimen. If the baby (11#) drinks 780 mL of milk a day
(2 - 2.5 ounces every 2 hours), what is his daily dose (mg)?
a) 0.1
b) 0.13 c) 2
d) 30
*e) 39
Mother’s blood average blood conc. is 2.5 mg/L therefore her milk conc. is 50
mg/L.
If the baby drinks 780 ml of milk he/she will get 39 mg of the drug.
16) Would you recommend mom stop breast feeding? (What % of the mom’s daily
dose (mg/kg) is the baby’s daily dose (mg/kg)?)
a) No, the child’s dose is less than 1% of the mother’s dose on a mg/kg/day basis.
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b) No, the child’s dose is about 5% of the mother’s dose on a mg/kg/day basis.
c) Maybe, the child’s dose is about 10% of the mother’s dose on a mg/kg/day basis.
*d) Yes, the child’s dose is about 50% of the mother’s dose on a mg/kg/day basis.
e) Yes, the child’s dose is about the same as the mother’s dose on a mg/kg/day
basis.
17) While Rifampin is not administered by IV infusion, what would be the infusion rate necessary to maintain an average plasma concentration of 2.5 mg/L (mg/
hr)? *a) 25 b) 50
c) 100 d) 150 e) 200
Vd = D/Cp0
= 400/10.02
= 39.9 L
Q = Cpss * K * Vd
= 2.5 * 0.25 * 39.9
= 25 mg/hr
18) While Rifampin is not administered by IV bolus, what would be the loading
dose necessary to obtain a plasma concentration of 2.5 mg/L (mg)? a) 25 b) 50
*c) 100 d) 150 e) 200
Loading Dose = Cpss * Vd
= 2.5 * 39.9
= 100mg
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19) While Rifampin is not administered by IV infusion, what would be the infusion rate necessary to obtain a plasma concentration of 2.5 mg/L in about 2.5 to 3
hours (mg/hr)? a) 25 *b) 50 c) 100 d) 150 e) 200
Cp = [Q/(K * Vd)] * (1 - e-kt)
Q = (Cp * K * Vd)/(1 - e-kt)
= (2.5mg/L * 0.25 * 39.9L)/[1 - e(-0.25 * 2.75)]
= 50 mg/hr
20) Rifampin is a semisynthetic derivative of rifamycin B, an antibiotic derived
from Streptomyces mediterranei. The minimum inhibitory concentration for N.
menengitidis is 0.1 - 1 mic/mL. It is distributed well into bodily fluids. About 30%
shows up in the urine as free drug and active metabolite while 60% shows up in the
feces as metabolite. The secretary is hounding me to finish the exam, so the
answer to 20 is a. Also, rifampin is 85% protien bound at physiological concentrations. *a) 25 b) 50 c) 100 d) 150 e) 200
Answers:
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Tmax
A
B
IV
1.27
1.7
0
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K
0.25
0.25
0.25
ka
2.66
1.37
---
AUC
53.9
57.7
39.8
Cpmax
10.6
9.9
10.02
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PHARMACOKINETICS SECOND HOUR PRACTICE EXAM #2
(1) Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:
a}Cpss b}feathering c}Wagner-Nelson method d}clearance e}f
(2) For each of the following pairs of variables (ordinate against abscissa), draw
a graph illustrating the qualitative profile of their relationship. Where appropriate, indicate the nature of important slopes, intercepts, and values. Unless your
specifically indicate on your plot that semi-log paper is being considered (write "SL"), it will be assumed that rectilinear paper is being considered. Graphs are for a
drug given by oral route where applicable.
a} total amount of drug collected minus the amount collected at the time in the
urine vs time
b} Plasma concentration of a drug given by oral route vs time
c} Plasma concentration of metabolite of a drug given by IV bolus vs time
d} Steady state plasma concentration vs infusion rate
e} Steaty state plasma consentration vs clearance
PHARMACOKINETICS SECOND HOUR PRACTICE EXAM #3
SECTION I
(1) Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:)
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a}Cpss b}f c}Absolute Bioavailability d}Comparative Bioavailability
(2) Compare and contrast:a}Wagner-Nelson and feathering methods
ment of plasma and urine data using Wagner-Nelson
b} Treat-
(3) For each of the following pairs of variables (ordinate against abscissa), draw
a graph illustrating the qualitative profile of their relationship. Where appropriate, indicate the nature of important slopes, intercepts, and values. Unless your
specifically indicate on your plot that semi-log paper is being considered (write "SL"), it will be assumed that rectilinear paper is being considered. Graphs are for a
drug given by oral route where applicable.
dXu/dt vs t for a drug given orally.
dXmu/dt vs t for a drug given by IV bolus.
Steady state plasma concentration vs infusion rate
Steady state plasma concentration vs elimination rate constant
PHARMACOKINETICS SECOND HOUR PRACTICE EXAM #4
SECTION I
1. Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:
a) clearance b)f c) absolute bioavailability d) comparative bioavailability e)
AUC
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2. By means of an annotated phase diagram explain how freeze-dried pharmaceutical injectables are made.
3. For each of the following pairs of variables (ordinate against abscissa) draw a
graph illustrating the qualitative profile of their relationship. Where appropriate,
indicate the nature of important slopes, intercepts, and values. Unless you specifically indicate on your plot that semi-log paper is being considered (write "SL"), it
will be assumed that rectilinear paper is being considered.
Pharmacological Response vs time
Peak time vs ka for oral dose
Fractional change in total body clearance vs. renal clearance
AUC vs ka
AUC vs ke
PHARMACOKINETICS SECOND HOUR PRACTICE EXAM #5
SECTION I
1. Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:
a) first pass effect b) f c) Intrinsic clearance
d) comparative bioavailability e) Extraction ratio
2. By means of an annotated phase diagram explain how a metastable polymorph
can be formed and how these polymorphs might effect the bioavailability of the
drug.
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3. For each of the following pairs of variables (ordinate against abscissa) draw a
graph illustrating the qualitative profile of their relationship. Where appropriate,
indicate the nature of important slopes, intercepts, and values. Unless your specifically indicate on your plot that semi-log paper is being considered (write "S-L"),
it will be assumed that rectilinear paper is being considered
fractional change in total body clearance vs plasma flow for drugs having a large
extraction ratio.
Peak time vs ka for oral dose
Fractional change in total body clearance vs. hepatic clearance.
AUC vs ka
AUC vs clearance
PHARMACOKINETICS SECOND HOUR PRACTICE EXAM #6
SECTION I
1. Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:
Henderson-Hasselbach relationship
Therapeutic alternatives
Therapeutic equivalents
comparative bioavailability
Extraction ratio
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Briefly discuss generic substitution by the pharmacist. Include such topics as when
it might be admissable and the liabilities involved.
3. For each of the following pairs of variables (ordinate against abscissa) draw a
graph illustrating the qualitative profile of their relationship. Where appropriate,
indicate the nature of important slopes, intercepts, and values. Unless you specifically indicate on your plot that semi-log paper is being considered (write "S-L"),
it will be assumed that rectilinear paper is being considered
a)
fractional change in total body clearance vs fractional change in plasma
flow for drugs having a small extraction ratio.
b)
Peak time vs dose for oral dose
c)
Fractional change in total body clearance vs. fractional change in hepatic
clearance for drugs having a large extration ratio.
d)
Ratio of milk to blood for basic drugs vs pKa.
e)
Ratio of milk to blood for acidic drugs vs pKa.
PHARMACOKINETICS SECOND HOUR PRACTICE EXAM #7
SECTION I
1. Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:
a) Bioequivalance
b) Intrinsic Clearance
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c) first pass effect
d) Henderson - Hasselbach equation
e) f
2.Compare and contrast absolute and relative bioavailability.
3.For each of the following pairs of variables (ordinate against abscissa) draw a
graph illustrating the qualitative profile of their relationship. Where appropriate,
indicate the nature of important slopes, intercepts, and values. Unless you specifically indicate on your plot that semi-log paper is being considered (write "S-L"),
it will be assumed that rectilinear paper is being considered
a)
Cpmax vs f for a drug given orally.
b)
Cpmax vs dose for a drug given orally.
c)
Cpmax vs Vd for a drug given orally.
d)
TBC vs Fi(H) for a drug with a high extraction ratio in the liver.
e)
TBC vs Fr(H) for a drug with a high extraction ratio in the liver
PHARMACOKINETICS SECOND HOUR PRACTICE EXAM #9
SECTION I
1. Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:
a) Henderson-Hasselbach relationship
b) Therapeutic alternatives
c) Therapeutic equivalents
d) Comparative bioavailability
e) Extraction ratio
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2. Briefly discuss generic substitution by the pharmacist. Include such topics as
when it might be admissible and the liabilities involved.
3. For each of the following pairs of variables (ordinate against abscissa) draw a
graph illustrating the qualitative profile of their relationship. Where appropriate,
indicate the nature of important slopes, intercepts, and values. Unless you specifically indicate on your plot that semi-log paper is being considered (write "SL"), it
will be assumed that rectilinear paper is being considered
a)
fractional change in total body clearance vs fractional change in plasma
flow for drugs having a small extraction ratio.
b)
Peak time vs dose for oral dose.
c)
Fractional change in total body clearance vs. fractional change in intrinsic
hepatic clearance for drugs having a large extraction ratio.
d)
Ratio of blood to milk concentrations for basic drugs vs pKa.
e)
Ratio of blood to milk concentrations for acidic drugs vs pKa.
PHARMACOKINETICS SECOND HOUR PRACTICE EXAM # 10
SECTION I
1. Succinctly define, stating rigorously the meaning of any symbols used and the
dimensions of measurement:
a) Henderson-Hasselbach relationship
b) Therapeutic alternatives
c) Therapeutic equivalents
d) Comparative bioavailability
e) Absolute bioavailability
f) Bioequivalents
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2. Compare and Contrast: Feathering and Wagner-Nelson method.
3. For each of the following pairs of variables (ordinate against abscissa), draw a
graph illustrating the qualitative profile of their relationship. Where appropriate,
indicate the nature of important slopes, intercepts, and values. Unless you indicate
on your plot that semi-log paper is being considered (write SL), it will be assumed
that rectilinear paper is being considered. Graphs are for a drug given by an oral
delivery system where applicable.
a)
Cpss vs. K
b)
Cp vs. ka
c)
Ratio of Milk to Blood for acidic drugs vs. pKa
Pharmacokinetics practice exam #11
Pharmaceutical alternatives may have different:
I. therapeutic moieties
II. dosage forms or strengths
III. salt or ester forms of the same therapeutic moiety
2) Pharmaceutical equivalents must have the same:
I. active ingredients and strength
II. dosage form and route of administration
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III. rate and extent of absorption
3) Bioequivalent drug products must have the same:
I. active ingredients and strength
II. dosage form and route of administration
III. rate and extent of absorption
4) Therapeutic equivalents are:
I. pharmaceutical alternatives
II. pharmaceutical equivalents
III. bioequivalents
5) The Wagner-Nelson method
I. uses curve stripping or feathering techniques
II. can be used to find ku and km
III. uses AUC calculations
6) The Federal guidelines for for bioequivalence require that the following pharmacokinetic parameters be within + 20 % of
the innovator’s product:
I. AUC, Peak time, Cpmax
II. Ka, Ke
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III. Vd
7) The steady state plasma concentration of a drug given by intravenous infusion is
dependent on:
I. length of time of of infusion
II. volume of distribution
III. elimination rate constant, K.
8) The peak time of a drug given by the oral route is dependent on:
I. the absorption rate constant
II. the metabolism rate constant
III. the excretion rate constant
9) The slope of the terminal portion of the graph of the metabolite of a drug which
(the drug, not the metabolite) was given
by intravenous bolus injection could be:
I. - the elimination rate constant of the metabolite
II. - the elimination rate constant of the drug
III. - the absorption rate constant of the metabolite
10) Comparative bioavailability includes calculations of the ratio(s) of the following pharmacokinetic parameters of two
oral products (generic / Innovator) normalized for dose :
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I. AUC (0 to Inf)
II. Peak time
III. Cpmax
Pharmacokinetics practice second hour exam #12
Where the are only three foils (possible quesses), please use K type system:
(NOTE: if foils are equivalent, all must be selected)
A) I ONLY
B) III ONLY
C) I AND II ONLY
D) II AND III ONLY
E) I, II, AND III
1) Steady state plasma concentration obtained by continuous infusion is inversely
proportional to:
I Infusion rate
II elimination rate constant
III volume of distribution
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2) Steady state plasma concentration obtained by continuous infusion is directly
proportional to:
I Infusion rate
II time
III volume of distribution
3) When calculating the AUC for an oral product using the trapezoidal rule, concentrations necessary to calculate the
first trapezoid are:
I the intercept of the extrapolated line of the plasma vs. time profile.
II the concentration at time zero, Cp0
III the concentration at the first time point
4) When calculating the AUC for an IV product using the trapezoidal rule, concentrations necessary to calculate the
first trapezoid are:
I the intercept of the extrapolated line of the plasma vs. time profile.
II the concentration at time zero, Cp0
III the concentration at the first time point
5) Absolute bioavailability is a calculation which
I must be between .80 and 1.20
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II compares an oral product to an IV bolus dose.
III is the ratio of the normalized AUCs of the products tested.
6) Comparative bioavailability is a calculation which
I is the ratio of the normalized AUCs of the products tested.
II must be between .80 and 1.20
III compares an oral product to an IV bolus dose.
7) When plotting the Wagner-Nelson function vs. time, a plot which proceeds horizontally for a measurable time and then
declines:
I is because of poor data in the early part of the data set.
II only the declining portion should be used to calculate ka.
III is an indication of a delay in release of the drug from the delivery system, a lag
time.
8) When considering ion trapping, comparing a drug which forms sulfate salts
distributing between mother’s milk and
blood, the ratio of total drug in milk to total drug in blood (Rm/b) can be
I greater than one.
II one.
III less than one.
9) When considering ion trapping, comparing a drug which forms sodium salts
distributing between mother’s milk and
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blood, the ratio of total drug in milk to total drug in blood (Rm/b) can be
I greater than one.
II one.
III less than one.
10) When using dry starch as a tablet disintegrating agent,
I tablet hardness is directly proportional to starch content.
II starch acts by allowing the water to wick into the tablet.
III a threshold minimum amount of starch is necessary before any disintegration
action is apparent.
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