Review Question - QID 109211

A 64-year-old female with a history of end-stage renal disease presents to her primary care physician complaining of weakness. She reports a six-month history of progressive weakness accompanied by occasional dull aching pain in her arms, legs, and lower back. She has also started to increase her fiber intake because of occasional strained bowel movements. Her past medical history is notable for poorly controlled diabetes, major depressive disorder, and obesity. She takes insulin and sertraline. She has a twenty pack-year smoking history and drinks alcohol socially. Her temperature is 98.5°F (36.9°C), blood pressure is 130/85 mmHg, pulse is 80/min, and respirations are 16/min. Laboratory findings are shown below:

Serum:
Na+: 138 mEq/L
Cl-: 99 mEq/L
K+: 3.9 mEq/L
HCO3-: 26 mEq/L
BUN: 20 mg/dL
Glucose: 140 mg/dL
Creatinine: 2.0 mg/dL
Parathyroid hormone: 720 µU/mL
Ca2+: 11.1 mg/dL
Phosphorus (inorganic): 4.8 mg/dl

A medication with which of the following mechanisms of action is most likely indicated to address this patient’s symptoms?