Aminophylline 500 mg is added to a 500 mL bag of IV fluid, to be administered over 12 hours. How much of the medication will infuse in 1 hour?

42 mg/hr. 500 mg/500 mL=1 mg/1 mL. To determine how much is administered for any amount of time, divide the total number of mL by the number of hours of infusion. 500 mL/12 hours = 41.66 mL/hr. Round up to 42 mL/hr.