If a nurse is to administer 30 mg of dextromethorphan and has a solution of 7.5 mg/5 mL, how much liquid should be given?

To determine how much liquid the nurse should administer for 30 mg of dextromethorphan using a solution concentration of 7.5 mg per 5 mL, one can calculate the volume needed based on the concentration provided.

First, find out how many milligrams are present in each milliliter of the solution. The concentration of 7.5 mg in 5 mL can be converted to a per-mL basis by dividing:

7.5 mg ÷ 5 mL = 1.5 mg/mL.

Next, to find out how many milliliters are required to reach the desired dose of 30 mg, the total amount needed (30 mg) can be divided by the concentration of 1.5 mg/mL:

30 mg ÷ 1.5 mg/mL = 20 mL.

Thus, the correct volume to administer in order to deliver 30 mg of dextromethorphan is 20 mL. This calculation ensures that the patient receives the appropriate dosage accurately based on the solution's concentration.