Worked example

Oral dose — liquid — practice problem 13

The prescriber orders 200 mg of ranitidine oral suspension. The bottle is labeled 400 mg per 5 mL.

Ordered dose200 mg
Concentration400 mg per 5 mL

How many milliliters should the nurse give?

Answer: 2.5 mL

Step-by-step solution

1. Identify what you have and what you want
Have: 400 mg per 5 mL · Want: 200 mg
2. Set up dimensional analysis so mg cancels
200 mg × ( 5 mL ÷ 400 mg )
3. Cancel mg and solve
= ( 200 × 5 ) ÷ 400 mL
= 2.5 mL

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