Question

Calculate doses for the drugs indicated below based on the patient’s BSA. Calculate theBSA to the nearest hundredth and medication dosages to the nearest tenth. Show complete solutions.

1. An adult who weighs 130 lbs and is 5 feet 6 inches needs methotrexate for cancer treatment. The recommended dose is 3.3-3.5 mg/m2/day. What is the daily dose for this patient?
a. Methotrexate is available as 2.5 mg/mL to be further diluted for IV infusion. How many mL would be added to the IV infusion for this patient per dose?

Answer 1

1.

5 feet 6 inches = 66 inches

= √ 130 * 66 / 3131   = √2.74 = 1.655 m2

Dose : 3.3-3.5 mg/m2/day

Minimum dose : 3.3 mg / m2 = 3.3 mg *1.655 m2/ m2 = 5.461 mg

Maximum dose : 3.5 mg / m2 = 3.5 mg *1.655 m2/ m2 = 5.792 mg

2.  Determine amount of drug to give based on dose ordered. Use dimensional analysis.

Ml/ mg = 1ml / 2.5mg   * 5.47 mg / 1 = 5.47 / 2.5 = 2.188 = 2.2 ml

Ml/ mg = 1ml / 2.5mg   * 5.79 mg / 1 = 5.79 / 2.5 = 2.316 = 2.3 ml