DOSAGE CALCULATIONS MADE
EASY
SOLVING PROBLEMS USING
DIMENSIONAL ANALYSIS
8TH EDITION
• AUTHOR(S)GLORIA PEARL
CRAIG
TEST BANK
,Question 1
The healthcare provider prescribes haloperidol 2.5 mg IM stat.
The available medication is haloperidol 5 mg/mL. How many mL
will the nurse administer?
A. 0.25 mL
B. 0.5 mL
C. 2 mL
D. 12.5 mL
Correct Answer:
B. 0.5 mL
Rationale:
Step 1: Identify the desired amount and the available
concentration. The order is for 2.5 mg. The available medication
is 5 mg per 1 mL.
Step 2: Set up the dimensional analysis equation to cancel out
the unwanted unit (mg) and solve for the desired unit (mL).
(2.5 mg) / 1 × (1 mL) / (5 mg) = ? mL
Step 3: Multiply the numerators and divide by the
denominators. The "mg" units cancel each other out.
(2.5 × 1 mL) / 5 = 2. = 0.5 mL
Medication Safety Note: Always double-check that the dosage
prescribed is appropriate for the patient's condition and that
,the correct concentration is selected to prevent a tenfold
overdose or underdose.
Question 2
A patient is prescribed acetaminophen 650 mg orally every 6
hours PRN for pain. The medication is available as a liquid with
a concentration of 160 mg/5 mL. How many teaspoons will the
nurse administer for each dose?
A. 1 teaspoon
B. 1.5 teaspoons
C. 2 teaspoons
D. 4 teaspoons
Correct Answer:
D. 4 teaspoons
Rationale:
Step 1: The order is for 650 mg. The concentration is 160 mg
per 5 mL. First, calculate the volume in mL to be administered.
(650 mg) × (5 mL) / (160 mg) = 20.3125 mL
Step 2: Convert the volume from mL to teaspoons. The standard
conversion factor is 1 teaspoon (tsp) = 5 mL.
20.3125 mL × (1 tsp) / (5 mL) = 4.0625 tsp
Step 3: Round to the nearest measurable dose, which is 4
teaspoons.
Medication Safety Note: Different liquid medications have
, different concentrations. Always verify the concentration on the
medication label and use a standard measuring device to
ensure an accurate dose, rather than a household spoon.
Question 3
The prescriber orders digoxin 125 mcg PO daily. The pharmacy
provides digoxin 0.25 mg tablets. How many tablets will the
nurse administer?
A. 0.5 tablets
B. 1 tablet
C. 1.25 tablets
D. 2 tablets
Correct Answer:
A. 0.5 tablets
Rationale:
Step 1: The order is in micrograms (mcg), but the available
medication is in milligrams (mg). Convert the ordered dose to
mg to match the available tablets. The conversion factor is 1000
mcg = 1 mg.
125 mcg × (1 mg) / (1000 mcg) = 0.125 mg
Step 2: Use dimensional analysis to find the number of tablets
needed.
0.125 mg × (1 tablet) / (0.25 mg) = 0.5 tablets
Step 3: Calculate the number of tablets.
EASY
SOLVING PROBLEMS USING
DIMENSIONAL ANALYSIS
8TH EDITION
• AUTHOR(S)GLORIA PEARL
CRAIG
TEST BANK
,Question 1
The healthcare provider prescribes haloperidol 2.5 mg IM stat.
The available medication is haloperidol 5 mg/mL. How many mL
will the nurse administer?
A. 0.25 mL
B. 0.5 mL
C. 2 mL
D. 12.5 mL
Correct Answer:
B. 0.5 mL
Rationale:
Step 1: Identify the desired amount and the available
concentration. The order is for 2.5 mg. The available medication
is 5 mg per 1 mL.
Step 2: Set up the dimensional analysis equation to cancel out
the unwanted unit (mg) and solve for the desired unit (mL).
(2.5 mg) / 1 × (1 mL) / (5 mg) = ? mL
Step 3: Multiply the numerators and divide by the
denominators. The "mg" units cancel each other out.
(2.5 × 1 mL) / 5 = 2. = 0.5 mL
Medication Safety Note: Always double-check that the dosage
prescribed is appropriate for the patient's condition and that
,the correct concentration is selected to prevent a tenfold
overdose or underdose.
Question 2
A patient is prescribed acetaminophen 650 mg orally every 6
hours PRN for pain. The medication is available as a liquid with
a concentration of 160 mg/5 mL. How many teaspoons will the
nurse administer for each dose?
A. 1 teaspoon
B. 1.5 teaspoons
C. 2 teaspoons
D. 4 teaspoons
Correct Answer:
D. 4 teaspoons
Rationale:
Step 1: The order is for 650 mg. The concentration is 160 mg
per 5 mL. First, calculate the volume in mL to be administered.
(650 mg) × (5 mL) / (160 mg) = 20.3125 mL
Step 2: Convert the volume from mL to teaspoons. The standard
conversion factor is 1 teaspoon (tsp) = 5 mL.
20.3125 mL × (1 tsp) / (5 mL) = 4.0625 tsp
Step 3: Round to the nearest measurable dose, which is 4
teaspoons.
Medication Safety Note: Different liquid medications have
, different concentrations. Always verify the concentration on the
medication label and use a standard measuring device to
ensure an accurate dose, rather than a household spoon.
Question 3
The prescriber orders digoxin 125 mcg PO daily. The pharmacy
provides digoxin 0.25 mg tablets. How many tablets will the
nurse administer?
A. 0.5 tablets
B. 1 tablet
C. 1.25 tablets
D. 2 tablets
Correct Answer:
A. 0.5 tablets
Rationale:
Step 1: The order is in micrograms (mcg), but the available
medication is in milligrams (mg). Convert the ordered dose to
mg to match the available tablets. The conversion factor is 1000
mcg = 1 mg.
125 mcg × (1 mg) / (1000 mcg) = 0.125 mg
Step 2: Use dimensional analysis to find the number of tablets
needed.
0.125 mg × (1 tablet) / (0.25 mg) = 0.5 tablets
Step 3: Calculate the number of tablets.
