Examples · Reconstitution
Worked example
Reconstitution - practice problem 3
The prescriber orders 250 mg of ceftriaxone IM. A 250 mg vial directs: add 0.9 mL of diluent to yield 250 mg/mL.
Ordered dose250 mg
Vial250 mg
Diluent0.9 mL
After reconstitution250 mg/mL
How many milliliters should the nurse draw up?
Answer: 1 mL
Step-by-step solution
1. Read the concentration after reconstitution
Add 0.9 mL diluent → 250 mg per 1 mL
2. Set up dimensional analysis so mg cancels
250 mg × ( 1 mL ÷ 250 mg )
3. Cancel mg and solve
= 250 ÷ 250 mL
= 1 mL
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