Based on the information below, what equivalent oral daily dose, in milligrams of theophylline, should the patient receive upon discharge?

Question

The drug aminophylline is 80% theophylline. A patient to be discharged from the hospital has been receiving aminophylline 40 mg/hour by IV infusion. Upon discharge, the physician orders oral theophylline tablets. The pharmacist recognizes that the prescribed tablets have 85% bioavailability. What equivalent oral daily dose, in milligrams of theophylline, should the patient receive upon discharge?

Answer 1

40 mg/hr x 24 hr/day = 960 mg aminophylline per day

80% of this is theophylline, thus... 960 mg x 0.80 = 768 mg theophylline per day.

Since the theophylline tables have only 85% bioavailability, the oral dose should be adjusted as follows:

768 mg / 0.85 = 904 mg of the theophylline tablets