Worked example

Reconstitution — practice problem 2

The prescriber orders 62.5 mg of ampicillin IV. The vial directs: add 10 mL of diluent to yield 125 mg/mL.

Ordered dose62.5 mg
After reconstitution125 mg/mL
Diluent10 mL

How many milliliters should the nurse draw up?

Answer: 0.5 mL

Step-by-step solution

1. Read the concentration after reconstitution
Add 10 mL diluent → 125 mg per 1 mL
2. Set up dimensional analysis so mg cancels
62.5 mg × ( 1 mL ÷ 125 mg )
3. Cancel mg and solve
= 62.5 ÷ 125 mL
= 0.5 mL

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