Worked example

Reconstitution — practice problem 1

The prescriber orders 125 mg of ampicillin IV. The vial directs: add 2 mL of diluent to yield 50 mg/mL.

Ordered dose125 mg
After reconstitution50 mg/mL
Diluent2 mL

How many milliliters should the nurse draw up?

Answer: 2.5 mL

Step-by-step solution

1. Read the concentration after reconstitution
Add 2 mL diluent → 50 mg per 1 mL
2. Set up dimensional analysis so mg cancels
125 mg × ( 1 mL ÷ 50 mg )
3. Cancel mg and solve
= 125 ÷ 50 mL
= 2.5 mL

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