The primary healthcare provider prescribes 4 mg of morphine intramuscularly. The vial reads morphine sulfate, 10 mg/mL. How many milliliters should be administered?

The primary healthcare provider prescribes 4 mg of morphine intramuscularly. The vial reads morphine sulfate, 10 mg/mL. How many milliliters should be administered?

• A. 0.2 mL
• B. 0.3 mL
• C. 0.4 mL
• D. 0.5 mL

Answer: (C)

When a dose is given in milligrams and the vial provides a concentration in milligrams per milliliter, you convert the dose to volume using volume = dose ÷ concentration. For 4 mg required with a concentration of 10 mg/mL, the volume you need is 4 ÷ 10 = 0.4 mL. Double-check by multiplying the volume back by the concentration: 0.4 mL × 10 mg/mL = 4 mg, which matches the prescribed amount. Therefore, administer 0.4 mL intramuscularly.

When a dose is given in milligrams and the vial provides a concentration in milligrams per milliliter, you convert the dose to volume using volume = dose ÷ concentration. For 4 mg required with a concentration of 10 mg/mL, the volume you need is 4 ÷ 10 = 0.4 mL. Double-check by multiplying the volume back by the concentration: 0.4 mL × 10 mg/mL = 4 mg, which matches the prescribed amount. Therefore, administer 0.4 mL intramuscularly.