TEST BANK BASED ON:
Calculating Drug Dosages
A Patient-Safe Approach to Nursing and Math
3rd Edition
• Author(s)Sandra Luz Martinez de Castillo;
Maryanne Werner-McCullough
Chapter 1 — Section 1.1: Principles of Safe Dosing
Stem: An antibiotic order reads: Give 250 mg IV. Available: 125
mg/5 mL vial. How many mL will you administer?
A. 1.0 mL
B. 2.0 mL
C. 10 mL
D. 20 mL
Correct Answer: C
Rationales:
• Correct (C): Concentration = 125 mg / 5 mL = 25 mg/mL.
Volume required = 250 mg ÷ 25 mg/mL = 10 mL.
, • A (1.0 mL): Reflects incorrect decimal placement
(assuming 250 mg = 250 mg/mL).
• B (2.0 mL): Likely calculated as 250 ÷ 125 = 2 but forgot to
account that 125 mg is in 5 mL (did not convert to mg/mL).
• D (20 mL): Twice the correct volume — likely double-
counting the 5 mL vial factor.
Teaching Point: Convert vial concentration to mg/mL before
calculating volume.
2.
Chapter 1 — Section 1.2: Unit Conversions (mcg ↔ mg)
Stem: Order: 0.5 mg of medication PO. Available: 250 mcg
tablets. How many tablets should the nurse give?
A. 1 tablet
B. 2 tablets
C. 0.5 tablet
D. 4 tablets
Correct Answer: B
Rationales:
• Correct (B): 0.5 mg = 500 mcg. Tablets are 250 mcg each →
500 mcg ÷ 250 mcg/tablet = 2 tablets.
• A (1): Mistake assuming 0.5 mg = 250 mcg.
, • C (0.5): Incorrectly converting or thinking halves of tablets
correspond to 0.5 mg (misplaced units).
• D (4): Possibly calculated 500 ÷ 125 (wrong tablet strength)
or misread units.
Teaching Point: Always convert mg to mcg when strengths are
in micrograms.
3.
Chapter 1 — Section 1.3: IV Infusion Rate (mL/hr)
Stem: Order: 1 g (1000 mg) IV over 4 hours. Drug bag: 1 g in
250 mL. What infusion rate (mL/hr) do you program? (Round
per usual policy to nearest whole mL/hr.)
A. 62 mL/hr
B. 63 mL/hr
C. 60 mL/hr
D. 66 mL/hr
Correct Answer: B
Rationales:
• Correct (B): Volume to infuse = 250 mL over 4 hours → 250
÷ 4 = 62.5 mL/hr, rounded to 63 mL/hr per whole mL/hr
rounding policy.
• A (62): Truncated instead of rounding (62.5 → 62).
, • C (60): Likely approximated (rounded down to a
convenient number) — underdosing risk.
• D (66): Incorrect rounding or miscalculation.
Teaching Point: Convert total volume/time, then apply facility
rounding rules.
4.
Chapter 1 — Section 1.4: Drop Factor Calculations (gtt/min)
Stem: Infuse 500 mL D5W over 4 hours using tubing with a 20
gtt/mL drop factor. What is the drops-per-minute rate
(gtt/min)?
A. 42 gtt/min
B. 41 gtt/min
C. 40 gtt/min
D. 50 gtt/min
Correct Answer: A
Rationales:
• Correct (A): gtt/min = (Volume × drop factor) ÷ (time in
minutes) = (500 mL × 20 gtt/mL) ÷ (4 × 60 min) = 10,000 ÷
240 = 41.6667 → 42 gtt/min (round to nearest whole
drop).
• B (41): Truncated instead of standard rounding.
• C (40): Rounding down too far (risk of under-infusion).
Calculating Drug Dosages
A Patient-Safe Approach to Nursing and Math
3rd Edition
• Author(s)Sandra Luz Martinez de Castillo;
Maryanne Werner-McCullough
Chapter 1 — Section 1.1: Principles of Safe Dosing
Stem: An antibiotic order reads: Give 250 mg IV. Available: 125
mg/5 mL vial. How many mL will you administer?
A. 1.0 mL
B. 2.0 mL
C. 10 mL
D. 20 mL
Correct Answer: C
Rationales:
• Correct (C): Concentration = 125 mg / 5 mL = 25 mg/mL.
Volume required = 250 mg ÷ 25 mg/mL = 10 mL.
, • A (1.0 mL): Reflects incorrect decimal placement
(assuming 250 mg = 250 mg/mL).
• B (2.0 mL): Likely calculated as 250 ÷ 125 = 2 but forgot to
account that 125 mg is in 5 mL (did not convert to mg/mL).
• D (20 mL): Twice the correct volume — likely double-
counting the 5 mL vial factor.
Teaching Point: Convert vial concentration to mg/mL before
calculating volume.
2.
Chapter 1 — Section 1.2: Unit Conversions (mcg ↔ mg)
Stem: Order: 0.5 mg of medication PO. Available: 250 mcg
tablets. How many tablets should the nurse give?
A. 1 tablet
B. 2 tablets
C. 0.5 tablet
D. 4 tablets
Correct Answer: B
Rationales:
• Correct (B): 0.5 mg = 500 mcg. Tablets are 250 mcg each →
500 mcg ÷ 250 mcg/tablet = 2 tablets.
• A (1): Mistake assuming 0.5 mg = 250 mcg.
, • C (0.5): Incorrectly converting or thinking halves of tablets
correspond to 0.5 mg (misplaced units).
• D (4): Possibly calculated 500 ÷ 125 (wrong tablet strength)
or misread units.
Teaching Point: Always convert mg to mcg when strengths are
in micrograms.
3.
Chapter 1 — Section 1.3: IV Infusion Rate (mL/hr)
Stem: Order: 1 g (1000 mg) IV over 4 hours. Drug bag: 1 g in
250 mL. What infusion rate (mL/hr) do you program? (Round
per usual policy to nearest whole mL/hr.)
A. 62 mL/hr
B. 63 mL/hr
C. 60 mL/hr
D. 66 mL/hr
Correct Answer: B
Rationales:
• Correct (B): Volume to infuse = 250 mL over 4 hours → 250
÷ 4 = 62.5 mL/hr, rounded to 63 mL/hr per whole mL/hr
rounding policy.
• A (62): Truncated instead of rounding (62.5 → 62).
, • C (60): Likely approximated (rounded down to a
convenient number) — underdosing risk.
• D (66): Incorrect rounding or miscalculation.
Teaching Point: Convert total volume/time, then apply facility
rounding rules.
4.
Chapter 1 — Section 1.4: Drop Factor Calculations (gtt/min)
Stem: Infuse 500 mL D5W over 4 hours using tubing with a 20
gtt/mL drop factor. What is the drops-per-minute rate
(gtt/min)?
A. 42 gtt/min
B. 41 gtt/min
C. 40 gtt/min
D. 50 gtt/min
Correct Answer: A
Rationales:
• Correct (A): gtt/min = (Volume × drop factor) ÷ (time in
minutes) = (500 mL × 20 gtt/mL) ÷ (4 × 60 min) = 10,000 ÷
240 = 41.6667 → 42 gtt/min (round to nearest whole
drop).
• B (41): Truncated instead of standard rounding.
• C (40): Rounding down too far (risk of under-infusion).
