Worked example

Oral dose — liquid — practice problem 5

The prescriber orders 50 mg of cephalexin oral suspension. The bottle is labeled 100 mg per 5 mL.

Ordered dose50 mg
Concentration100 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: 100 mg per 5 mL · Want: 50 mg
2. Set up dimensional analysis so mg cancels
50 mg × ( 5 mL ÷ 100 mg )
3. Cancel mg and solve
= ( 50 × 5 ) ÷ 100 mL
= 2.5 mL

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