A physician orders ondansetron (Zofran) 2 mg IV. If the vial contains 4 mg/5 mL, how much should be administered?

To determine the correct volume of ondansetron to administer, you'll need to use the concentration provided in the vial. The vial contains 4 mg of ondansetron in 5 mL, which gives a concentration of 0.8 mg/mL (4 mg / 5 mL).

The physician has ordered a dose of 2 mg. To calculate how much volume in mL corresponds to this dose, you can use the formula:

Volume (mL) = Dose (mg) / Concentration (mg/mL)

Substituting the values:

Volume = 2 mg / 0.8 mg/mL = 2.5 mL

Thus, the correct amount to administer is 2.5 mL, which matches the calculation and confirms why this answer is correct. This demonstrates understanding both of how to convert between the dose ordered and the concentration in the vial to arrive at the appropriate volume.