CSPT - Compounded Sterile Preparation Technician Sterile Compounding Calculations 1 — Questions and Answers
Question 1: A 500 mL bag of 0.9% sodium chloride is ordered to infuse over 4 hours using a 15 gtt/mL administration set. What is the required flow rate in drops per minute?
- 21 gtt/min
- 31 gtt/min (Correct answer)
- 42 gtt/min
- 63 gtt/min
Correct answer: 31 gtt/min
Flow rate (gtt/min) = (Volume × drop factor) ÷ time in minutes = (500 mL × 15 gtt/mL) ÷ (4 hr × 60 min/hr) = 7,500 ÷ 240 = 31.25, rounded to 31 gtt/min.
Question 2: A ceftriaxone 1 g powder vial is reconstituted with 9.6 mL of sterile water for injection, yielding a total volume of 10 mL. What is the resulting concentration?
- 50 mg/mL
- 75 mg/mL
- 100 mg/mL (Correct answer)
- 200 mg/mL
Correct answer: 100 mg/mL
Concentration = amount of drug ÷ final volume = 1,000 mg ÷ 10 mL = 100 mg/mL. Always use the final reconstituted volume, not the diluent volume added.
Question 3: A patient is ordered a heparin infusion at 1,200 units/hr. The bag is prepared as 25,000 units of heparin in 500 mL D5W. At what rate should the infusion pump be set?
- 12 mL/hr
- 18 mL/hr
- 24 mL/hr (Correct answer)
- 30 mL/hr
Correct answer: 24 mL/hr
First find the concentration: 25,000 units ÷ 500 mL = 50 units/mL. Then rate = dose ÷ concentration = 1,200 units/hr ÷ 50 units/mL = 24 mL/hr.
Question 4: How many mL of a 70% dextrose solution must be mixed with sterile water for injection to prepare 500 mL of a 10% dextrose solution?
- 35.7 mL
- 71.4 mL (Correct answer)
- 100.0 mL
- 142.9 mL
Correct answer: 71.4 mL
Using alligation: parts of 70% = (10 − 0) = 10 parts; parts of water = (70 − 10) = 60 parts; total = 70 parts. Volume of 70% solution = (10 ÷ 70) × 500 mL = 71.4 mL.
Question 5: A 60-kg patient requires gentamicin 2 mg/kg IV every 8 hours. The available vial is labeled 40 mg/mL. How many mL should be drawn up for each dose?
- 1.5 mL
- 2.0 mL
- 3.0 mL (Correct answer)
- 4.5 mL
Correct answer: 3.0 mL
Step 1 — calculate the dose: 2 mg/kg × 60 kg = 120 mg. Step 2 — calculate the volume: 120 mg ÷ 40 mg/mL = 3 mL per dose.
Question 6: A TPN order calls for a continuous infusion at 80 mL/hr for 24 hours. How many 1,000 mL bags will the pharmacy need to prepare?
- 1 bag
- 2 bags (Correct answer)
- 3 bags
- 4 bags
Correct answer: 2 bags
Total volume needed = 80 mL/hr × 24 hr = 1,920 mL. Dividing by 1,000 mL per bag = 1.92 bags, which must be rounded up to 2 bags to cover the full 24-hour infusion.
CSPT - Compounded Sterile Preparation Technician Sterile Compounding Calculations 1
A 500 mL bag of 0.9% sodium chloride is ordered to infuse over 4 hours using a 15 gtt/mL administration set.
What is the required flow rate in drops per minute?