Worked example

Oral dose — liquid — practice problem 2

The prescriber orders 75 mg of cephalexin oral suspension. The bottle is labeled 50 mg per 5 mL.

Ordered dose75 mg
Concentration50 mg per 5 mL

How many milliliters should the nurse give?

Answer: 7.5 mL

Step-by-step solution

1. Identify what you have and what you want
Have: 50 mg per 5 mL · Want: 75 mg
2. Set up dimensional analysis so mg cancels
75 mg × ( 5 mL ÷ 50 mg )
3. Cancel mg and solve
= ( 75 × 5 ) ÷ 50 mL
= 7.5 mL

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