CSPT Compounding Calculations 5 — Questions and Answers
Question 1: A pediatric patient needs gentamicin 2.5 mg/kg IV q8h. The child weighs 22 lbs. What is the single dose in mg?
- 12.5 mg (Correct answer)
- 25 mg
- 27.5 mg
- 55 mg
Correct answer: 12.5 mg
22 lbs ÷ 2.2 = 10 kg; 10 kg × 2.5 mg/kg = 25 mg — answer index 1 is 25 mg.
Question 2: How many mL of sterile water for injection must be added to 50 mL of a 50% dextrose solution to produce a 25% dextrose solution?
- 25 mL
- 50 mL (Correct answer)
- 75 mL
- 100 mL
Correct answer: 50 mL
C1V1 = C2V2 → 50% × 50 mL = 25% × V2 → V2 = 100 mL; SWFI needed = 100 − 50 = 50 mL.
Question 3: A morphine PCA bag contains 50 mg in 50 mL NS. The PCA is programmed for 1 mg demand doses. What volume delivers each demand dose?
- 0.5 mL
- 1 mL (Correct answer)
- 2 mL
- 5 mL
Correct answer: 1 mL
Concentration = 50 mg/50 mL = 1 mg/mL; 1 mg dose ÷ 1 mg/mL = 1 mL.
Question 4: Amino acids provide 4 kcal/g. A TPN contains 85 g of amino acids. How many kcal do the amino acids contribute?
- 85 kcal
- 170 kcal
- 255 kcal
- 340 kcal (Correct answer)
Correct answer: 340 kcal
85 g × 4 kcal/g = 340 kcal.
Question 5: You are preparing an IV admixture and need to add calcium gluconate 1 g. The available vial is 10% (100 mg/mL). How many mL do you draw up?
- 1 mL
- 5 mL
- 10 mL (Correct answer)
- 100 mL
Correct answer: 10 mL
1 g = 1000 mg; 1000 mg ÷ 100 mg/mL = 10 mL.
Question 6: A compounding technician must prepare 600 mL of a 0.45% NaCl solution using 0.9% NaCl stock and SWFI. How much 0.9% NaCl is needed?
- 100 mL
- 200 mL
- 300 mL (Correct answer)
- 450 mL
Correct answer: 300 mL
C1V1 = C2V2: 0.9% × V1 = 0.45% × 600 mL → V1 = 300 mL.
Question 7: A pharmacist verifies an order for cyclosporine 3 mg/kg/day for a 70 kg patient. The available concentration is 50 mg/mL. What daily volume should be prepared?
- 2.1 mL
- 4.2 mL (Correct answer)
- 7 mL
- 14 mL
Correct answer: 4.2 mL
Dose = 3 × 70 = 210 mg/day; 210 mg ÷ 50 mg/mL = 4.2 mL.
CSPT Compounding Calculations 5
A pediatric patient needs gentamicin 2.5 mg/kg IV q8h.
The child weighs 22 lbs.
What is the single dose in mg?