Fluoxetine 40 mg PO daily. The amount available is Fluoxetine 20 mg/5 mL. How many mL should the nurse administer?

Fluoxetine 40 mg PO daily. The amount available is Fluoxetine 20 mg/5 mL. How many mL should the nurse administer?

• A. 5 mL
• B. 10 mL
• C. 15 mL
• D. 20 mL

Answer: (B)

When solving this, focus on converting the drug’s concentration to a per-milliliter value and then use that to reach the prescribed dose. The concentration is 20 mg in 5 mL, which means 4 mg per 1 mL. To deliver 40 mg, calculate the volume needed: 40 mg ÷ 4 mg/mL = 10 mL. So the nurse should administer 10 mL. For context, 5 mL would provide 20 mg, 15 mL would provide 60 mg, and 20 mL would provide 80 mg, which are not the prescribed 40 mg.

When solving this, focus on converting the drug’s concentration to a per-milliliter value and then use that to reach the prescribed dose. The concentration is 20 mg in 5 mL, which means 4 mg per 1 mL. To deliver 40 mg, calculate the volume needed: 40 mg ÷ 4 mg/mL = 10 mL. So the nurse should administer 10 mL. For context, 5 mL would provide 20 mg, 15 mL would provide 60 mg, and 20 mL would provide 80 mg, which are not the prescribed 40 mg.