A practical nurse is preparing to administer a scheduled dose of cefazolin 750\text{ mg} i… — NCLEX-PN

A practical nurse is preparing to administer a scheduled dose of cefazolin $750\text{ mg}$ intramuscularly (IM) to a client with a skin infection. The medication is supplied as a $1\text{ gram}$ vial of dry powder. The reconstitution instructions on the vial state: "Add $2.5\text{ mL}$ of sterile water for injection to yield a final concentration of $330\text{ mg/mL}$ ."

How many $\text{mL}$ should the nurse administer? Record the answer to the nearest tenth. Do not include units in the answer.

Answer: 2.3 mL

Answer

2.3

The correct volume is found by dividing the desired dose (

750\text{ mg}

) by the available concentration (

330\text{ mg}

per

1\text{ mL}

), which equals

2.2727... \text{ mL}

. Rounded to the nearest tenth, this is

2.3\text{ mL}

. Note that the

1\text{ gram}

total powder amount and the

2.5\text{ mL}

diluent volume are distractors and should not be used in the final equation once the final concentration is known.

Step-by-Step Solution

Identify the target dose and available concentration from the provided instructions.

Target dose:

750\text{ mg}

, Concentration:

330\text{ mg/mL}

These are the essential values needed to calculate the physical volume to be administered.

Apply the standard dosage calculation formula:

\frac{\text{Desired}}{\text{Have}} \times \text{Volume}

\frac{750\text{ mg}}{330\text{ mg}} \times 1\text{ mL} = 2.2727... \text{ mL}

This formula converts the prescribed medication mass into the correct physical volume based on the reconstituted concentration.

Round the calculated volume to the nearest tenth as instructed.

2.2727... \text{ mL}

rounds to

2.3\text{ mL}

Standard rounding rules dictate that a hundredths digit of

5

or greater rounds the tenths digit up.

Key Concept

Dosage Calculation for Reconstituted Medications

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