DOSAGE CALCULATIONS MADE
EASY
SOLVING PROBLEMS USING
DIMENSIONAL ANALYSIS
8TH EDITION
• AUTHOR(S)GLORIA PEARL
CRAIG
TEST BANK
,A primary care provider prescribes levothyroxine 0.125 mg PO
daily for a client with hypothyroidism. The pharmacy dispenses
levothyroxine 50 mcg tablets. How many tablets will the nurse
administer per dose?
A. 0.5 tablets
B. 1.5 tablets
C. 2 tablets
D. 2.5 tablets
Correct Answer: D
Rationale:
• Step 1: Identify the ordered dose ($0.125\text{ mg}$) and
the available unit ($50\text{ mcg}$ per tablet). The target
unit is tablets.
• Step 2: Set up the equation using dimensional analysis to
convert milligrams to micrograms and determine the
number of tablets.
$$\text{tablets} = \frac{1\text{ tablet}}{50\text{ mcg}} \times
\frac{1,000\text{ mcg}}{1\text{ mg}} \times \frac{0.125\text{
mg}}{1}$$
• Step 3: Calculate the final value by canceling out matching
units.
,$$\text{tablets} = \frac{1 \times 1,000 \times 0.125}{50 \times
1 \times 1} = \frac{125}{50} = 2.5\text{ tablets}$$
Medication Safety Note: Levothyroxine doses are frequently
ordered in milligrams but supplied in micrograms.
Misinterpreting the decimal point or failing to perform a proper
metric conversion is a common source of medication errors that
can lead to severe hypo- or hyperthyroidism.
Question 2 (Easy: Household-to-Metric Conversion)
A home health nurse is instructing a client on how to take
prescribed lactulose syrup 20 g PO twice daily. The medication
label states: Lactulose 10 g per 15 mL. The nurse should instruct
the client to measure how many tablespoons using a calibrated
medication cup?
A. 1 tablespoon
B. 2 tablespoons
C. 3 tablespoons
D. 4 tablespoons
Correct Answer: B
Rationale:
• Step 1: Identify the ordered dose ($20\text{ g}$), the
available concentration ($10\text{ g} / 15\text{ mL}$), and
, the household conversion factor ($1\text{ tablespoon
[tbsp]} = 15\text{ mL}$).
• Step 2: Set up the dimensional analysis equation to find
tablespoons.
$$\text{tbsp} = \frac{1\text{ tbsp}}{15\text{ mL}} \times
\frac{15\text{ mL}}{10\text{ g}} \times \frac{20\text{ g}}{1}$$
• Step 3: Cancel out units and solve.
$$\text{tbsp} = \frac{1 \times 15 \times 20}{15 \times 10 \times
1} = \frac{300}{150} = 2\text{ tbsp}$$
Medication Safety Note: Household spoons
(teaspoons/tablespoons) vary significantly in volume and must
never be used for medication administration. Clients should
always use a calibrated measuring device supplied by the
pharmacy to ensure accurate dosing.
Question 3 (Easy: Oral Medication)
The provider prescribes extended-release potassium chloride
40 mEq PO daily. The pharmacy provides potassium chloride 20
mEq extended-release tablets. How many tablets will the nurse
administer?
A. 0.5 tablets
B. 1 tablet
C. 1.5 tablets
EASY
SOLVING PROBLEMS USING
DIMENSIONAL ANALYSIS
8TH EDITION
• AUTHOR(S)GLORIA PEARL
CRAIG
TEST BANK
,A primary care provider prescribes levothyroxine 0.125 mg PO
daily for a client with hypothyroidism. The pharmacy dispenses
levothyroxine 50 mcg tablets. How many tablets will the nurse
administer per dose?
A. 0.5 tablets
B. 1.5 tablets
C. 2 tablets
D. 2.5 tablets
Correct Answer: D
Rationale:
• Step 1: Identify the ordered dose ($0.125\text{ mg}$) and
the available unit ($50\text{ mcg}$ per tablet). The target
unit is tablets.
• Step 2: Set up the equation using dimensional analysis to
convert milligrams to micrograms and determine the
number of tablets.
$$\text{tablets} = \frac{1\text{ tablet}}{50\text{ mcg}} \times
\frac{1,000\text{ mcg}}{1\text{ mg}} \times \frac{0.125\text{
mg}}{1}$$
• Step 3: Calculate the final value by canceling out matching
units.
,$$\text{tablets} = \frac{1 \times 1,000 \times 0.125}{50 \times
1 \times 1} = \frac{125}{50} = 2.5\text{ tablets}$$
Medication Safety Note: Levothyroxine doses are frequently
ordered in milligrams but supplied in micrograms.
Misinterpreting the decimal point or failing to perform a proper
metric conversion is a common source of medication errors that
can lead to severe hypo- or hyperthyroidism.
Question 2 (Easy: Household-to-Metric Conversion)
A home health nurse is instructing a client on how to take
prescribed lactulose syrup 20 g PO twice daily. The medication
label states: Lactulose 10 g per 15 mL. The nurse should instruct
the client to measure how many tablespoons using a calibrated
medication cup?
A. 1 tablespoon
B. 2 tablespoons
C. 3 tablespoons
D. 4 tablespoons
Correct Answer: B
Rationale:
• Step 1: Identify the ordered dose ($20\text{ g}$), the
available concentration ($10\text{ g} / 15\text{ mL}$), and
, the household conversion factor ($1\text{ tablespoon
[tbsp]} = 15\text{ mL}$).
• Step 2: Set up the dimensional analysis equation to find
tablespoons.
$$\text{tbsp} = \frac{1\text{ tbsp}}{15\text{ mL}} \times
\frac{15\text{ mL}}{10\text{ g}} \times \frac{20\text{ g}}{1}$$
• Step 3: Cancel out units and solve.
$$\text{tbsp} = \frac{1 \times 15 \times 20}{15 \times 10 \times
1} = \frac{300}{150} = 2\text{ tbsp}$$
Medication Safety Note: Household spoons
(teaspoons/tablespoons) vary significantly in volume and must
never be used for medication administration. Clients should
always use a calibrated measuring device supplied by the
pharmacy to ensure accurate dosing.
Question 3 (Easy: Oral Medication)
The provider prescribes extended-release potassium chloride
40 mEq PO daily. The pharmacy provides potassium chloride 20
mEq extended-release tablets. How many tablets will the nurse
administer?
A. 0.5 tablets
B. 1 tablet
C. 1.5 tablets
