The question asks how much volume should be withdrawn from a bulk vancomycin solution based on given details.

Information provided:

• The bulk package contains 10 g of vancomycin reconstituted with 95 mL of water, yielding a concentration of 500 mg/5 mL.
• The label on the compounded solution indicates 1.25 g of vancomycin in 500 mL of D5W.

Step-by-Step Approach:

1. Concentration in the bulk package:

   • The reconstituted solution contains 10 g of vancomycin in 95 mL of water.
   • $10 \, \text{g} = 10,000 \, \text{mg}$.
   • Therefore, the concentration of the bulk package is: $\text{Concentration} = \frac{10,000 \, \text{mg}}{95 \, \text{mL}} = 105.26 \, \text{mg/mL}$

2. Amount required:

   • The label reads 1.25 g (or 1,250 mg) of vancomycin in the final preparation.
   • To find the volume needed to get 1,250 mg from the bulk package (with concentration $105.26 \, \text{mg/mL}$): $\text{Volume} = \frac{1,250 \, \text{mg}}{105.26 \, \text{mg/mL}} \approx 11.87 \, \text{mL}$

The closest answer to this value from the provided options is D. 12.5 mL.

Do you need further clarification or details? Here are five questions to further explore this concept:

1. How do you calculate the concentration of a medication in solution?
2. What steps are involved in converting grams to milligrams?
3. How can you verify if a reconstituted solution has the correct concentration?
4. What are the typical dilution methods used in compounding medications?
5. How would changes in reconstitution volume affect the concentration of a drug?

Tip: Always ensure you’re clear on whether units need to be converted (e.g., grams to milligrams) before performing calculations.