A physician orders 0.2 mg of a medication to be administered subcutaneously from a stock solution of 0.4 mg/mL. What volume should be drawn?

To determine the correct volume of medication to draw from the stock solution, the first step is to understand the concentration of the stock solution and the required dose.

The stock solution concentration is 0.4 mg/mL, meaning each milliliter of this solution contains 0.4 mg of medication. The physician has ordered a dose of 0.2 mg. To find out how much volume corresponds to this dose from the stock solution, you can use the formula:

Volume (mL) = Dose (mg) / Concentration (mg/mL)

Substituting the known values into the formula:

Volume = 0.2 mg / 0.4 mg/mL = 0.5 mL

This calculation shows that to deliver a dose of 0.2 mg, a volume of 0.5 mL should be drawn from the stock solution. Therefore, the answer is 0.5 mL, confirming that selecting this volume will achieve the desired medication administration correctly.

This process illustrates how to utilize the concentration of a solution to accurately determine the amount of fluid needed to provide a specific dosage of medication, which is a fundamental concept in pharmacology and medication administration.