Saunders Comprehensive Review for the NCLEX-PN®
Examination
9th Edition
• Author(s)Linda Anne Silvestri; Angela Silvestri
TEST BANK
1) Pediatric mg/kg — oral suspension
An infant weighs 35 lb. The provider orders amoxicillin 15
mg/kg/dose PO q12h. The pharmacy supplies amoxicillin oral
suspension 250 mg/5 mL. How many mL should be given per
dose? Round to the nearest tenth (0.1 mL).
A. 4.8 mL
B. 5.7 mL
C. 6.0 mL
D. 4.3 mL
Answer: B. 5.7 mL
Step-by-step (dimensional analysis & digit-by-digit arithmetic):
1. Convert pounds to kilograms:
35 lb ÷ 2.2 = 15.909090909... → 15.909... kg (keep full
digits for following step).
, 2. Calculate dose in mg:
15.9090909 kg × 15 mg/kg = 238.6363636... mg →
238.6363636 mg.
3. Use concentration to find mL: 250 mg per 5 mL →
(238.6363636 mg) × (5 mL / 250 mg) =
First compute ratio: 5 ÷ 250 = 0.02 mL per mg.
238.6363636 mg × 0.02 mL/mg = 4.772727272 mL →
4.7727... mL.
4. Rounding to nearest tenth: 4.8 mL. Wait—this numeric
result indicates 4.8 mL — but check arithmetic: We must
re-check step 2 carefully: 15.9090909 × 15 =
15 × 15.9090909 = (15 × 15) + (15 × 0.9090909) = 225 +
13.6363635 = 238.6363635 mg (same). Then times 0.02 =
4.77272727 mL → rounds to 4.8 mL.
Therefore correct answer is A (4.8 mL). (Important: initial
choice corrected by arithmetic audit — A is correct.)
Correct answer (final): A. 4.8 mL
Rationale (correct): Converting lb → kg then applying mg/kg
gives the mg dose. Using the suspension concentration (mg per
mL) converted by dimensional analysis yields the mL volume.
This follows Saunders’ stepwise dimensional analysis approach
(convert units, multiply by conversion factors). Elsevier Health
Why the incorrect options would be chosen (and why wrong):
• B (5.7 mL): likely from mistakenly using 20 mg/kg instead
of 15 mg/kg or dividing incorrectly. Incorrect dose factor.
, • C (6.0 mL): likely rounding early (rounding kg to 16 kg then
calculating). Error due to premature rounding.
• D (4.3 mL): probably from converting with an erroneous
conversion factor (e.g., 1 kg = 2.5 lb) or arithmetic slip.
Teaching point / safety check: Always convert lb → kg first,
keep extra significant digits through calculations, and only
round the final answer as instructed. Confirm pediatric doses
against recommended mg/kg ranges and check for allergies.
2) Weight-based IV infusion (mcg/kg/min → mL/hr)
Order: Dopamine 5 mcg/kg/min IV. Patient weight 70 kg.
Concentration available: 400 mg dopamine diluted in 250 mL
D5W (note: dopamine strengths often given in mg — convert
mg → mcg). Calculate the infusion pump rate in mL/hr. Round
to nearest whole mL/hr.
A. 62 mL/hr
B. 16 mL/hr
C. 21 mL/hr
D. 31 mL/hr
Answer: C. 21 mL/hr
Step-by-step calculation (digit-by-digit):
1. Convert ordered dose from mcg → mg, or convert
concentration to mcg/mL. Start with ordered rate: 5
, mcg/kg/min. Patient: 70 kg.
70 kg × 5 mcg/kg/min = 350 mcg/min → 350 mcg/min.
2. Convert mcg/min → mcg/hr: 350 mcg/min × 60 min/hr =
21,000 mcg/hr → 21,000 mcg/hr.
3. Convert mcg to mg (1 mg = 1000 mcg): 21,000 mcg/hr ÷
1000 = 21 mg/hr.
4. Concentration available: 400 mg in 250 mL →
concentration = 400 mg ÷ 250 mL = 1.6 mg/mL. (Digit
check: 400 ÷ 250 = 1.6 mg/mL).
5. Find mL/hr needed for 21 mg/hr: 21 mg/hr ÷ (1.6 mg/mL)
= 13.125 mL/hr → 13.125 mL/hr. Rounding to nearest
whole mL/hr → 13 mL/hr.
But none of the answer options match 13 mL/hr. Re-check step
3: Is conversion correct? Wait — alternative common pitfall:
dopamine concentrations are sometimes expressed as mg in
250 mL, but some clinicians convert dose in mcg/kg/min to
mL/hr by using formula:
mL/hr = (mcg/kg/min × kg × 60 × mL per mg) ÷ 1000 (mcg per
mg)
We did that and obtained 13.125 mL/hr.
Given options, none equal 13. So likely the concentration in the
stem meant 400 mg in 250 mL (1.6 mg/mL) — result 13 mL/hr.
Since option C is 21 mL/hr and closest to 13 might reflect
common mis-step converting mg vs mcg. Therefore question
must be corrected — the correct computed answer is 13
Examination
9th Edition
• Author(s)Linda Anne Silvestri; Angela Silvestri
TEST BANK
1) Pediatric mg/kg — oral suspension
An infant weighs 35 lb. The provider orders amoxicillin 15
mg/kg/dose PO q12h. The pharmacy supplies amoxicillin oral
suspension 250 mg/5 mL. How many mL should be given per
dose? Round to the nearest tenth (0.1 mL).
A. 4.8 mL
B. 5.7 mL
C. 6.0 mL
D. 4.3 mL
Answer: B. 5.7 mL
Step-by-step (dimensional analysis & digit-by-digit arithmetic):
1. Convert pounds to kilograms:
35 lb ÷ 2.2 = 15.909090909... → 15.909... kg (keep full
digits for following step).
, 2. Calculate dose in mg:
15.9090909 kg × 15 mg/kg = 238.6363636... mg →
238.6363636 mg.
3. Use concentration to find mL: 250 mg per 5 mL →
(238.6363636 mg) × (5 mL / 250 mg) =
First compute ratio: 5 ÷ 250 = 0.02 mL per mg.
238.6363636 mg × 0.02 mL/mg = 4.772727272 mL →
4.7727... mL.
4. Rounding to nearest tenth: 4.8 mL. Wait—this numeric
result indicates 4.8 mL — but check arithmetic: We must
re-check step 2 carefully: 15.9090909 × 15 =
15 × 15.9090909 = (15 × 15) + (15 × 0.9090909) = 225 +
13.6363635 = 238.6363635 mg (same). Then times 0.02 =
4.77272727 mL → rounds to 4.8 mL.
Therefore correct answer is A (4.8 mL). (Important: initial
choice corrected by arithmetic audit — A is correct.)
Correct answer (final): A. 4.8 mL
Rationale (correct): Converting lb → kg then applying mg/kg
gives the mg dose. Using the suspension concentration (mg per
mL) converted by dimensional analysis yields the mL volume.
This follows Saunders’ stepwise dimensional analysis approach
(convert units, multiply by conversion factors). Elsevier Health
Why the incorrect options would be chosen (and why wrong):
• B (5.7 mL): likely from mistakenly using 20 mg/kg instead
of 15 mg/kg or dividing incorrectly. Incorrect dose factor.
, • C (6.0 mL): likely rounding early (rounding kg to 16 kg then
calculating). Error due to premature rounding.
• D (4.3 mL): probably from converting with an erroneous
conversion factor (e.g., 1 kg = 2.5 lb) or arithmetic slip.
Teaching point / safety check: Always convert lb → kg first,
keep extra significant digits through calculations, and only
round the final answer as instructed. Confirm pediatric doses
against recommended mg/kg ranges and check for allergies.
2) Weight-based IV infusion (mcg/kg/min → mL/hr)
Order: Dopamine 5 mcg/kg/min IV. Patient weight 70 kg.
Concentration available: 400 mg dopamine diluted in 250 mL
D5W (note: dopamine strengths often given in mg — convert
mg → mcg). Calculate the infusion pump rate in mL/hr. Round
to nearest whole mL/hr.
A. 62 mL/hr
B. 16 mL/hr
C. 21 mL/hr
D. 31 mL/hr
Answer: C. 21 mL/hr
Step-by-step calculation (digit-by-digit):
1. Convert ordered dose from mcg → mg, or convert
concentration to mcg/mL. Start with ordered rate: 5
, mcg/kg/min. Patient: 70 kg.
70 kg × 5 mcg/kg/min = 350 mcg/min → 350 mcg/min.
2. Convert mcg/min → mcg/hr: 350 mcg/min × 60 min/hr =
21,000 mcg/hr → 21,000 mcg/hr.
3. Convert mcg to mg (1 mg = 1000 mcg): 21,000 mcg/hr ÷
1000 = 21 mg/hr.
4. Concentration available: 400 mg in 250 mL →
concentration = 400 mg ÷ 250 mL = 1.6 mg/mL. (Digit
check: 400 ÷ 250 = 1.6 mg/mL).
5. Find mL/hr needed for 21 mg/hr: 21 mg/hr ÷ (1.6 mg/mL)
= 13.125 mL/hr → 13.125 mL/hr. Rounding to nearest
whole mL/hr → 13 mL/hr.
But none of the answer options match 13 mL/hr. Re-check step
3: Is conversion correct? Wait — alternative common pitfall:
dopamine concentrations are sometimes expressed as mg in
250 mL, but some clinicians convert dose in mcg/kg/min to
mL/hr by using formula:
mL/hr = (mcg/kg/min × kg × 60 × mL per mg) ÷ 1000 (mcg per
mg)
We did that and obtained 13.125 mL/hr.
Given options, none equal 13. So likely the concentration in the
stem meant 400 mg in 250 mL (1.6 mg/mL) — result 13 mL/hr.
Since option C is 21 mL/hr and closest to 13 might reflect
common mis-step converting mg vs mcg. Therefore question
must be corrected — the correct computed answer is 13
