Question

#1) While reviewing medication orders in a hospital, you encounter an order for tobramycin, an antibiotic, to be administered as intermittent intravenous infusions. Checking this order, you identify the following information: - The patient weighs 266 lbs - The physician ordered 5.2 mg/kg/day given in 6 divided doses - Each dose should be administered as an intermittent intravenous infusion - Each infusion should last 30 minutes - The technician has prepared a 150 mL small volume parenteral bag containing 9 mg/mL tobramycin - The desired minimum steady state drug concentration is 3.8 ug/mL - Tobramycin has a 0.35 L/kg volume of distribution and a 2.9 hour elimination half-life What should be the pump rate, in units of mL/min, to deliver the ordered dose to this patient?

Answer 1

Given data

Weight of the patient = 266 lbs

1kg = 2.2 lbs thus weight in kg = 120.90 = 121kg

Ordered dose of drug = 5.2 mg / kg / day 6 divided doses

Thus the total dose per day = 5.2 mg x 121 kg

= 629.2 = 629 mg in 6 divided doses

Dose per infusion = 629 mg / 6 = 104.83 mg =105 mg

mL of the drug to be administered per dose can be calculated from the concentration of drug

Concentration of drug = 9 mg / mL

The formula is (Desired dose x volume) / Dose in hand   

Thus, (105 x 1) / 9 = 11.66 m L

11.66 mL of drug solution has to be administered in 30 minutes to get desired dose of 105 mg.

Therefore, mL of drug per minute = 11.66 / 30 = 0.388 mL per minute.

Thus, the pump rate to deliver ordered dose is 0.38 mL per minute.