Chapter 1 —Medication Orders & Tablet
Calculations
Stem
A provider writes an order for digoxin 0.125 mg. Which written
form of the dose is the safest to include on the MAR to avoid
decimal errors?
Options
A. 0.125 mg
B. .125 mg
C. 0.125mg (no space)
D. 0.125 mg IV stat (with trailing zero written as 0.1250 mg)
,Correct Answer
A
Rationales
• Correct (A): 0.125 mg uses a leading zero and a space
before units — recommended to prevent misreading and
transcription errors.
• B (.125 mg): Missing leading zero increases risk of a
tenfold error (nurse could read “.125” as “125”).
• C (0.125mg no space): Omitting the space between the
numeric dose and unit can lead to transcription errors or
misinterpretation.
• D (0.1250 mg): Contains unnecessary trailing zero, which
risks misreading (e.g., 0.1250 → 0.125 or 1.250), and is
discouraged.
Teaching Point
Always use a leading zero and a clear space before units.
2
Chapter Reference
Chapter 1 — Section 1.2: Units & Conversions — mg ↔ g
Stem
Order: Ampicillin 0.5 g PO. The pharmacy supplies 250 mg
tablets. How many tablets should the nurse administer?
,Options
A. 1 tablet
B. 2 tablets
C. 3 tablets
D. 4 tablets
Correct Answer
B
Rationales
• Correct (B): Convert grams to milligrams: 0.5 g = 0.5 ×
1000 = 500 mg. Tablets per dose = 500 mg ÷ 250 mg/tablet
= 2 tablets.
• A (1 tablet): Reflects error of not converting g → mg or
halving dose (500 mg ÷ 250 = 2, not 1).
• C (3 tablets): Common arithmetic mistake (e.g., 500 ÷ 250
≈ 2, not 3).
• D (4 tablets): Reflects 10× error or misreading 250 mg as
125 mg.
Teaching Point
Always convert to same units before dividing to find tablets.
3
Chapter Reference
Chapter 1 — Section 1.3: Concentration Calculations
, Stem
A medication is prepared as 1,000 mg in 250 mL IV solution.
What is the concentration in mg/mL?
Options
A. 2 mg/mL
B. 4 mg/mL
C. 0.25 mg/mL
D. 25 mg/mL
Correct Answer
B
Rationales
• Correct (B): 1,000 mg ÷ 250 mL = 4 mg/mL. Step: 1000/250
= 4.
• A (2 mg/mL): Probably halved the numerator or doubled
the volume (1000 ÷ 500 = 2).
• C (0.25 mg/mL): Misplaced decimal (1000 ÷ 4000 or 250 ÷
1000).
• D (25 mg/mL): Off by factor of ~6.25 — likely a division
error.
Teaching Point
Compute mg per mL by dividing total mg by total volume (mL).
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Calculations
Stem
A provider writes an order for digoxin 0.125 mg. Which written
form of the dose is the safest to include on the MAR to avoid
decimal errors?
Options
A. 0.125 mg
B. .125 mg
C. 0.125mg (no space)
D. 0.125 mg IV stat (with trailing zero written as 0.1250 mg)
,Correct Answer
A
Rationales
• Correct (A): 0.125 mg uses a leading zero and a space
before units — recommended to prevent misreading and
transcription errors.
• B (.125 mg): Missing leading zero increases risk of a
tenfold error (nurse could read “.125” as “125”).
• C (0.125mg no space): Omitting the space between the
numeric dose and unit can lead to transcription errors or
misinterpretation.
• D (0.1250 mg): Contains unnecessary trailing zero, which
risks misreading (e.g., 0.1250 → 0.125 or 1.250), and is
discouraged.
Teaching Point
Always use a leading zero and a clear space before units.
2
Chapter Reference
Chapter 1 — Section 1.2: Units & Conversions — mg ↔ g
Stem
Order: Ampicillin 0.5 g PO. The pharmacy supplies 250 mg
tablets. How many tablets should the nurse administer?
,Options
A. 1 tablet
B. 2 tablets
C. 3 tablets
D. 4 tablets
Correct Answer
B
Rationales
• Correct (B): Convert grams to milligrams: 0.5 g = 0.5 ×
1000 = 500 mg. Tablets per dose = 500 mg ÷ 250 mg/tablet
= 2 tablets.
• A (1 tablet): Reflects error of not converting g → mg or
halving dose (500 mg ÷ 250 = 2, not 1).
• C (3 tablets): Common arithmetic mistake (e.g., 500 ÷ 250
≈ 2, not 3).
• D (4 tablets): Reflects 10× error or misreading 250 mg as
125 mg.
Teaching Point
Always convert to same units before dividing to find tablets.
3
Chapter Reference
Chapter 1 — Section 1.3: Concentration Calculations
, Stem
A medication is prepared as 1,000 mg in 250 mL IV solution.
What is the concentration in mg/mL?
Options
A. 2 mg/mL
B. 4 mg/mL
C. 0.25 mg/mL
D. 25 mg/mL
Correct Answer
B
Rationales
• Correct (B): 1,000 mg ÷ 250 mL = 4 mg/mL. Step: 1000/250
= 4.
• A (2 mg/mL): Probably halved the numerator or doubled
the volume (1000 ÷ 500 = 2).
• C (0.25 mg/mL): Misplaced decimal (1000 ÷ 4000 or 250 ÷
1000).
• D (25 mg/mL): Off by factor of ~6.25 — likely a division
error.
Teaching Point
Compute mg per mL by dividing total mg by total volume (mL).
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