A nurse is preparing to administer cefazolin 500 mg IM every 8 hr. Available is cefazolin 1 g vial. The package insert instructs adding sterile water 2.5 mL to yield cefazolin 330 mg/mL. How many mL should the nurse administer per dose? (Round the answer to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero.)
The Correct Answer and Explanation is :
To determine the amount of cefazolin to administer per dose, follow these steps:
- Calculate the concentration of cefazolin in the vial:
- The package insert indicates that adding 2.5 mL of sterile water to the cefazolin vial results in a concentration of 330 mg/mL.
- Determine the required dose:
- The ordered dose is 500 mg of cefazolin.
- Use the concentration to calculate the volume needed:
- The formula to calculate the volume (V) required is: V=DoseConcentrationV = \frac{\text{Dose}}{\text{Concentration}}V=ConcentrationDose
- Plug in the values: V=500 mg330 mg/mLV = \frac{500 \text{ mg}}{330 \text{ mg/mL}}V=330 mg/mL500 mg
- Perform the calculation:V=500330≈1.515V = \frac{500}{330} \approx 1.515V=330500≈1.515
- Round the answer to the nearest tenth:
- Rounding 1.515 to the nearest tenth gives 1.5 mL.
Explanation:
To prepare and administer the medication, it’s crucial to accurately calculate the volume of the drug solution needed based on the concentration provided. In this case, the vial of cefazolin is reconstituted to a concentration of 330 mg/mL. Given that the ordered dose is 500 mg, the calculation involves dividing the dose by the concentration to determine how many milliliters of solution are needed.
By dividing 500 mg by 330 mg/mL, you obtain approximately 1.515 mL. This result is then rounded to the nearest tenth for practical administration purposes. Rounding 1.515 mL to the nearest tenth gives 1.5 mL. This is the volume of cefazolin solution that should be administered for each dose.
This process ensures that the patient receives the correct dose of medication, maintaining both efficacy and safety. Proper rounding is essential in clinical settings to avoid dosage errors that could impact patient outcomes.