Worked example

Oral dose — liquid — practice problem 4

The prescriber orders 375 mg of cephalexin oral suspension. The bottle is labeled 250 mg per 1 mL.

Ordered dose375 mg
Concentration250 mg per 1 mL

How many milliliters should the nurse give?

Answer: 1.5 mL

Step-by-step solution

1. Identify what you have and what you want
Have: 250 mg per 1 mL · Want: 375 mg
2. Set up dimensional analysis so mg cancels
375 mg × ( 1 mL ÷ 250 mg )
3. Cancel mg and solve
= ( 375 × 1 ) ÷ 250 mL
= 1.5 mL

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