Worked example

Reconstitution — practice problem 6

The prescriber orders 300 mg of cefazolin IV. The vial directs: add 5 mL of diluent to yield 100 mg/mL.

Ordered dose300 mg
After reconstitution100 mg/mL
Diluent5 mL

How many milliliters should the nurse draw up?

Answer: 3 mL

Step-by-step solution

1. Read the concentration after reconstitution
Add 5 mL diluent → 100 mg per 1 mL
2. Set up dimensional analysis so mg cancels
300 mg × ( 1 mL ÷ 100 mg )
3. Cancel mg and solve
= 300 ÷ 100 mL
= 3 mL

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