A 600 mg antibiotic IM is prescribed. The vial contains 300 mg per 5 mL. How many milliliters should be drawn?

A 600 mg antibiotic IM is prescribed. The vial contains 300 mg per 5 mL. How many milliliters should be drawn?

• A. 5 mL
• B. 15 mL
• C. 20 mL
• D. 10 mL

Answer: (D)

You determine how many milliliters to draw using the vial’s concentration and the desired dose. The vial has 300 mg in 5 mL, which means 60 mg per 1 mL (300 ÷ 5 = 60 mg/mL). To get 600 mg, you need 600 ÷ 60 = 10 mL. Another way to see it: 600 mg is double 300 mg, so you draw double the volume of 5 mL, which is 10 mL. If you drew 5 mL you’d get 300 mg; 15 mL would give 900 mg, etc. Therefore, draw 10 mL.

You determine how many milliliters to draw using the vial’s concentration and the desired dose. The vial has 300 mg in 5 mL, which means 60 mg per 1 mL (300 ÷ 5 = 60 mg/mL). To get 600 mg, you need 600 ÷ 60 = 10 mL. Another way to see it: 600 mg is double 300 mg, so you draw double the volume of 5 mL, which is 10 mL. If you drew 5 mL you’d get 300 mg; 15 mL would give 900 mg, etc. Therefore, draw 10 mL.