You receive an order for compazine 10 mg IM. The vial on hand reads 10 mL, 5 mg/mL. How many milliliters will you administer?

You receive an order for compazine 10 mg IM. The vial on hand reads 10 mL, 5 mg/mL. How many milliliters will you administer?

• A. 0.5 mL
• B. 2 mL
• C. 1 mL
• D. 5 mL

Answer: (B)

Converting a prescribed dose to the volume to administer using the vial’s concentration is the key idea. You know you need 10 mg and the vial provides 5 mg in every 1 mL. The volume needed is Dose ÷ (Concentration) = 10 mg ÷ (5 mg/mL) = 2 mL. A quick check confirms the math: 2 mL × 5 mg/mL = 10 mg, which matches the ordered dose. The vial total is 10 mL, so drawing 2 mL leaves 8 mL in the vial, but that doesn’t affect the dose calculation.

Converting a prescribed dose to the volume to administer using the vial’s concentration is the key idea. You know you need 10 mg and the vial provides 5 mg in every 1 mL. The volume needed is Dose ÷ (Concentration) = 10 mg ÷ (5 mg/mL) = 2 mL. A quick check confirms the math: 2 mL × 5 mg/mL = 10 mg, which matches the ordered dose. The vial total is 10 mL, so drawing 2 mL leaves 8 mL in the vial, but that doesn’t affect the dose calculation.