The practical nurse (PN) is preparing cefazolin 400 mg IM for a client with a gram-positive infection. The available vial is labeled, “Cefazolin 1 gram,” and the instructions for reconstitution state, for IM use, add 2 mL sterile water for injection. Total volume after reconstitution is 2.5 mL. After reconstitution, how many mL should be administered to the client? (Enter numeric value only. If rounding is required, round to the whole number, nearest tenths/hundredth).
The Correct answer and Explanation is:
To administer the correct dosage of cefazolin, follow these steps to determine how many milliliters to administer:
- Understand the Concentration After Reconstitution:
- The vial of cefazolin is labeled “Cefazolin 1 gram,” which means it contains 1000 mg of cefazolin.
- After reconstitution with 2 mL of sterile water, the total volume is 2.5 mL.
- Calculate the Concentration of the Solution:
- To find the concentration of the reconstituted solution, divide the total amount of drug by the total volume of the solution.
- Concentration (mg/mL) = Total Amount of Drug (mg) / Total Volume (mL)
- Concentration = 1000 mg / 2.5 mL = 400 mg/mL
- Determine the Volume Required to Administer 400 mg:
- The client requires a dose of 400 mg.
- Using the concentration calculated, determine how many mL of the solution is needed to achieve the required dose.
- Volume to administer (mL) = Desired Dose (mg) / Concentration (mg/mL)
- Volume = 400 mg / 400 mg/mL = 1 mL
Therefore, 1 mL of the reconstituted cefazolin solution should be administered to the client to provide the required dose of 400 mg.
Explanation:
When preparing medications, accurate calculations are crucial to ensure proper dosing and avoid errors. In this scenario, the reconstitution of cefazolin creates a solution with a known concentration. By understanding this concentration, you can determine how much of the solution to draw up to deliver the correct dose.
In reconstitution, the addition of a diluent changes the concentration of the medication. The concentration tells us how many milligrams of medication are present per milliliter of solution. By dividing the total amount of medication by the total volume, you find the concentration. Then, to calculate the volume needed for the desired dose, you divide the dose by the concentration.
The accuracy of this calculation ensures the client receives the correct amount of medication, which is essential for effective treatment and avoiding complications or side effects associated with incorrect dosing.