Patient W.L. received a 20 mg intravenous (IV) bolus dose of…
Patient W.L. received a 20 mg intravenous (IV) bolus dose of pamidronate for the treatment of Paget’s disease of bone. Plasma samples were collected 15 minutes and 5 hours after administration. The measured plasma concentrations were: C15min = 76.6 µg/L, C5h = 68.1 µg/L. Assume that pamidronate follows a one-compartment pharmacokinetic model with first-order elimination. (17 pts. total) a. To improve therapeutic response, the physician decides to administer pamidronate by continuous IV infusion and wishes to achieve a target steady-state plasma concentration (Css) of 200 µg/L. Calculate the IV infusion rate required to achieve the desired steady-state concentration in this patient. (9 pts.) b. Calculate the plasma concentration of pamidronate 4 hours after the IV infusion is initiated. (2 pts.) c. One month later, Patient W.L. returns for a second treatment course. Due to a severe intra-abdominal infection, his renal function has declined, and his creatinine clearance (CrCL) has decreased from 110 mL/min to 65 mL/min. Assume that 46% of an IV dose of pamidronate is excreted unchanged in urine. To maintain the target Css of 200 µg/L, calculate the following: (i) IV infusion rate (4 pts.); (ii) Loading dose (2 pts.).
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