Worked example

Oral dose - liquid - practice problem 13

The prescriber orders 25 mg of diphenhydramine oral solution. The bottle is labeled 12.5 mg per 5 mL.

Ordered dose25 mg
Concentration12.5 mg per 5 mL

How many milliliters should the nurse give?

Answer: 10 mL

Step-by-step solution

1. Identify what you have and what you want
Have: 12.5 mg per 5 mL · Want: 25 mg
2. Set up dimensional analysis so mg cancels
25 mg × ( 5 mL ÷ 12.5 mg )
3. Cancel mg and solve
= ( 25 × 5 ) ÷ 12.5 mL
= 10 mL

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