If a physician orders 25 mg of a medication to be given intramuscularly and the available concentration is 40 mg/mL, what is the amount of drug to be drawn?

To determine the amount of drug to be drawn from the available concentration, it is essential to calculate the volume of medication needed to administer the prescribed dose. The physician has ordered 25 mg of medication, and you have a concentration of 40 mg/mL.

To find out how many milliliters correspond to 25 mg, you can use the formula:

[ \text{Volume (mL)} = \frac{\text{Dose (mg)}}{\text{Concentration (mg/mL)}} ]

Substituting the known values into this formula:

[ \text{Volume (mL)} = \frac{25 \text{ mg}}{40 \text{ mg/mL}} = 0.625 \text{ mL} ]

This calculation shows that to administer 25 mg of the medication, you need to draw 0.625 mL from the vial where the concentration is 40 mg/mL. Therefore, the amount of drug to be drawn is 0.625 mL, making it the correct choice for this problem. The calculation demonstrates an application of basic pharmacology principles surrounding dosing and drug concentrations, which is fundamental for safe medication administration.