Patient W.L. was given IV bolus injection of 20 mg of Pamidr…
Patient W.L. was given IV bolus injection of 20 mg of Pamidronate to treat his Paget’s disease of bone. Following the IV bolus injection, blood samples were collected from Patient W.L. at 15 minutes and 5 hours. Pamidronate plasma concentrations determined were: C15min = 76.6 µg/L, C5h = 68.1 µg/L. (17 pts. total) To improve the response, the physician decided to give Pamidronate to the patient as intravenous infusion that can maintain a Css of 200 µg/L. Calculate the infusion rate needed to achieve the desired Pamidronate Css of 200 µg/L in this patient. Assume one-compartment kinetics with zero order input and 1st order elimination. (9 pts.) Calculate the Pamidronate plasma concentration at 4 hours after the IV infusion starts. (2 pts.) A month later when Patient W.L. came back to receive the 2nd round of treatment, his CrCl changed from 110 mL/min to 65 mL/min due to impaired renal function caused by a severe intra-abdominal infection. Assume 46% of Pamidronate IV dose is excreted in the urine as unchanged drug. To maintain the Pamidronate Css at 200 µg/L in Patient W.L., calculate the: (i) IV infusion rate (4 pts.); (ii) Loading dose (2 pts.).