Compounding Calculations Flashcards

A pediatric patient needs gentamicin 2.5 mg/kg IV q8h. The child weighs 22 lbs. What is the single dose in mg?

Answer: 12.5 mg

22 lbs ÷ 2.2 = 10 kg; 10 kg × 2.5 mg/kg = 25 mg — answer index 1 is 25 mg.

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?

Answer: 50 mL

C1V1 = C2V2 → 50% × 50 mL = 25% × V2 → V2 = 100 mL; SWFI needed = 100 − 50 = 50 mL.

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?

Answer: 1 mL

Concentration = 50 mg/50 mL = 1 mg/mL; 1 mg dose ÷ 1 mg/mL = 1 mL.

Amino acids provide 4 kcal/g. A TPN contains 85 g of amino acids. How many kcal do the amino acids contribute?

Answer: 340 kcal

85 g × 4 kcal/g = 340 kcal.

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?

Answer: 10 mL

1 g = 1000 mg; 1000 mg ÷ 100 mg/mL = 10 mL.

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?

Answer: 300 mL

C1V1 = C2V2: 0.9% × V1 = 0.45% × 600 mL → V1 = 300 mL.

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?

Answer: 4.2 mL

Dose = 3 × 70 = 210 mg/day; 210 mg ÷ 50 mg/mL = 4.2 mL.