You regularly order six 10-ml vials per month of a drug that has a concentration of 50 mg/ml. Now that same drug is only available in 20-ml vials of 10 mg/ml. How many vials should you order this month?

You regularly order six 10-ml vials per month of a drug that has a concentration of 50 mg/ml. Now that same drug is only available in 20-ml vials of 10 mg/ml. How many vials should you order this month?

• A. 15 vials
• B. 10 vials
• C. 20 vials
• D. 25 vials

Answer: (A)

You’re keeping the same total drug amount each month, so start by figuring out how many milligrams you need with the old packaging. Six vials per month, each 10 ml at 50 mg/ml, gives 6 × 10 × 50 = 3000 mg per month. With the new packaging, each vial contains 20 ml at 10 mg/ml, so each vial has 20 × 10 = 200 mg. To meet the 3000 mg monthly need, divide 3000 by 200, which equals 15 vials. So, you should order 15 vials to supply the same monthly amount. This illustrates converting the monthly dose to total milligrams, then dividing by the new vial’s milligrams per vial.

You’re keeping the same total drug amount each month, so start by figuring out how many milligrams you need with the old packaging. Six vials per month, each 10 ml at 50 mg/ml, gives 6 × 10 × 50 = 3000 mg per month.

With the new packaging, each vial contains 20 ml at 10 mg/ml, so each vial has 20 × 10 = 200 mg.

To meet the 3000 mg monthly need, divide 3000 by 200, which equals 15 vials.

So, you should order 15 vials to supply the same monthly amount. This illustrates converting the monthly dose to total milligrams, then dividing by the new vial’s milligrams per vial.