NAPLEX PRACTICE QUESTIONS2 1 ca l cu l a t i on ques t i on s t o
p repa re f o r t he boa rd exams
RxCa l cu l a t i ons
MICHAEL DANQUAH , MS , PHD
C O N T E N T S
0 3
08
1 0
1 5
1 7
2 2
2 5
2 8
3 2
CONVERS IONS
TOTA L PARENTERA L NUTR I T I ON
CONCENTRAT ION
PH AND BUF FERS
M I L L I EQU I VA L ENTS
OSMOLAR I T Y
RECONST I TU T ION
F LOW RATE CA LCU LA T IONS
ANSWERS
N A P L E X P R A C T I C E Q U E S T I O N S
C O N V E R S I O N S
LEARN YOUR CONVERSION FACTORS AND
PRACTICE HOW TO USE THEM
PAGE 3
QUESTION 1
How many milligrams
are equal to 1/150 gr of
Nitroglycerine?
PAGE 4
R E V I EW HOW T O CONV ER T F ROM
GRA I N T O M I L L I G R AM
QUESTION 2
How many grams of
Heparin are required
to prepare 1 quart of
0.45% solution?
PAGE 5
R E V I EW HOW T O CONV ER T F ROM
QUAR T T O M I L L I L I T E R S
QUESTION 3
If I want to make a
gallon of cough
preparation that will
contain 1 grain of
active ingredient per
teaspoonful. How
many grams of active
ingredient will I need?
PAGE 6
R E V I EW HOW T O CONV ER T F ROM
GRA I N T O GRAMS AND GA L L ON S T O
L I T E R S
QUESTION 4
If a prescription reads
“Augmentin 875 mg po
bid x 10 days,” how
many mL of
Augmentin 250 mg/5
mL are required to fill a
ten-day supply?
PAGE 7
R E V I EW HOW T O SO L V E A DA Y S
S U P P L Y T Y P E P ROB L EM
T O T A L P A R E N T E R A L
N U T R I T I O N
PRACTICE USING CONVERSION FACTORS
AND EQUATIONS FOR TPN CALCULATIONS
PAGE 8
QUESTION 5
JM is a patient in the ICU
(6'1" and 256 pounds). He is
currently receiving 3-in-1
PN at 125 mL/h. The PN is
12.1% w/v dextrose and
4.7%w/v protein. The
prescriber wants the
patient's protein intake
from the PN to be 1.4 g/kg
IBW per day. By how many
grams will the current
protein need to be reduced
to achieve this?
PAGE 9
R E V I EW HOW T O SO L V E A T PN T Y P E
P ROB L EM
C O N C E N T R A T I O N
REVIEW THE VARIOUS WAYS OF
EXPRESSICONVERSION FACTORS
AND EQUATIONS FOR TPN CALCULATIONS
PAGE 10
QUESTION 6
If 60 g of 1%
hydrocortisone are
mixed with 80 g of
2.5% hydrocortisone,
what is the
percent of
hydrocortisone in the
final mixture?
PAGE 11
R E V I EW HOW T O SO L V E F OR F I N A L
CONC EN T RA T I ON O F A P R E PARA T I ON
G I V EN T H E CONC EN T RA T I ON AND
QUAN T I T I E S O F COMPONEN T S T O B E
COMB I N ED
QUESTION 7
How many mL of 75%
alcohol should be
mixed with 10%
alcohol to prepare 30%
of 500 mL alcohol
solution ?
PAGE 12
R E V I EW HOW T O SO L V E F OR F I N A L
CONC EN T RA T I ON O F A P R E PARA T I ON
G I V EN T H E CONC EN T RA T I ON AND
QUAN T I T I E S O F COMPONEN T S T O B E
COMB I N ED
QUESTION 8
An ointment contains
1%w/w calamine. How
much calamine
powder would be
appropriate to add to a
200g of the ointment
to produce a 4% w/w
calamine ointment?
PAGE 13
HOW T O SO L V E A D I L U T I ON S AND
CONC EN T RA T I ON QUE S T I ON U S I N G
T H E A L L I G A T I ON ME THOD
QUESTION 9
How much Lidocaine is
required to prepare 30
mL of a 1:1000
Lidocaine solution?
PAGE 14
HOW T O SO L V E A RA T I O S T R ENG TH
CA L CU L A T I ON S P ROB L EM
P H A N D B U F F E R S
PRACTICE KEY CONCEPTS IN PH AND
BUFFER CALCULATIONS
PAGE 15
QUESTION 10
What is the ratio of
ionized to unionized
species of a weakly
acidic drug at pH = 7 if
the pKa = 5?
PAGE 16
HOW T O SO L V E A PH AND BU F F E R
CA L CU L A T I ON S P ROB L EM U S I N G T H E
HENDER SON - HA S S E L B A L CH EQUA T I ON
M I L L I E Q U I V A L E N T S
PRACTICE USING KEY EQUATIONS
IN MILLIEQUIVALENTS CALCULATIONS
PAGE 17
QUESTION 11
How many mEqs of K+
are present in 750 mg
of a KCl capsule? [ K+ =
39, Cl- = 35.5]
PAGE 18
HOW T O SO L V E F OR
M I L L I E QU I V A L EN T S O F AN I O N G I V EN
T H E MAS S AND MOL E CU L AR WE I GH T
QUESTION 12
How many grams of
CaCl2 are required to
prepare a 1 gallon
solution that contains
20 mEq of calcium
ions? [mw CaCl2 =
111g/mol]
PAGE 19
HOW T O SO L V E F OR T H E QUAN T I T Y O F
A S A L T NE ED ED T O S U P P L Y A G I V EN
M I L L I E QU I V A L EN T O F AN I O N
QUESTION 13
If a prescription calls to
dispense 8 fl oz of KCl
in such a way that 1
teaspoonful of solution
contains 0.5 mEqs of
drug, how many grams
of KCl are required to
prepare the above
prescription? [mw of
KCl = 74.5g/mol]
PAGE 20
HOW T O SO L V E F OR T H E QUAN T I T Y O F
A S A L T NE ED ED T O S U P P L Y A G I V EN
M I L L I E QU I V A L EN T O F AN I O N
QUESTION 14
You receive a prescription
for 240 mL of a potassium
citrate solution with a
concentration of 15
mEq/15mL. How much
potassium citrate must
you weigh out to
compound this
prescription? (MW of
C6H5K3O7 = 306)
PAGE 21
HOW T O SO L V E F OR T H E QUAN T I T Y O F
A S A L T NE ED ED T O S U P P L Y A G I V EN
M I L L I E QU I V A L EN T O F AN I O N G I V EN
T H E CONC EN T RA T I ON O F T H E
SO L U T I ON
O S M O L A R I T Y
PRACTICE USING KEY EQUATIONS
IN OSMOLARITY CALCULATIONS
PAGE 22
QUESTION 15
How many mOsmols/L
are represented by
1000 mL 0.9% sodium
chloride solution?
PAGE 23
HOW T O CA L CU L A T E OSMO LAR I T Y
G I V EN T H E CONC EN T RA T I ON O F T H E
SO L U T I ON
QUESTION 16
How many mOsmols/L
are represented by a
50 mL 8.4% sodium
bicarbonate solution?
[mw = 84 g/mol]
PAGE 24
HOW T O CA L CU L A T E OSMO LAR I T Y
G I V EN T H E CONC EN T RA T I ON O F T H E
SO L U T I ON
R E C O N S T I T U T I O N
PRACTICE KEY CONCEPTS IN
RECONSTITUTION CALCULATIONS
PAGE 25
QUESTION 17
A patient is ordered a 130
mg dose of a drug in 50
mL of D5W. A vial
contains 1 gram of the
powdered drug. The drug
has a powder volume of
0.4 mL. How many
milliliters will be needed
to fill the patient order if
the concentration after
reconstitutions is 250
mg/mL?
PAGE 26
HOW T O CA L CU L A T E T H E VO LUME O F A
R E CON S T I T U T ED SO L U T I ON NE ED ED T O
F I L L A PA T I E N T S ORDER
QUESTION 18
Your bottle of Amoxil
(amoxicillin) says to
add 39 mL to the bottle
to get a solution of 150
mg/tsp. The total
amount in the bottle is
2 g. What is the
powder volume?
PAGE 27
HOW T O CA L CU L A T E POWDER VO LUME
F L O W R A T E S
PRACTICE KEY CONCEPTS IN FLOW
RATE CALCULATIONS
PAGE 28
QUESTION 19
Four grams of
Levofloxacin (mixed
with 500 mL 0.9%
NaCl) is administered
via slow I.V. infusion
over 24 hours. If the I.V.
set delivers 10
drops/ml, what would
be the rate of flow in
drops/ min?
PAGE 29
HOW T O DE T E RM I N E F L OW RA T E I N
DROP S P E R M INU T E
QUESTION 20
A 60-kg patient is to
receive a constant
infusion of dobutamine
at a rate of 5
mcg/kg/min. The
available solution has a
concentration of 0.5
mg/mL. For what rate
should the infusion
pump be set?
PAGE 30
HOW T O DE T E RM I N E F L OW RA T E O F AN
I N F U S I ON PUMP I N M I L L I L I T E R S P E R
HOUR
QUESTION 21
A patient is receiving an
IV 1000 cc per 8 hour.
When 600 mL have been
run in from the 1-L bag,
the physician ordered the
remainder to be infused
over the next 6 hours. The
IV set is calibrated at 10
gtt/mL. What is the new
flow rate in drops per
minute?
PAGE 31
HOW T O DE T E RM I N E F L OW RA T E I N
DROP S P E R M INU T E
ANSWERS
1. 0.432 mg
2. 4.26 g
3. 49 g
4. 350 mL
5. 29.14 g
6. 3.5 drops/min
7. 153.85 mL
8. 6.25 g
9. 30 mg
10. 100:1
11. 10 mEq
PAGE 32
12. 1.11 g
13. 1.788 g
14. 24.48 g
15. 307.7 mOsm/L
16. 2000 mOsm/L
17. 0.52 mL
18. 27.67 mL
19. 3.5 drops/min
20. 36 mL/h
21. 11.1 drops/min
G E T M O R E N A P L E X
P R A C T I C E Q U E S T I O N S
T O D A Y
L E A R N M O R E
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