In addition to dietary counseling regarding a low phosphate diet, this patient with stage G4/A1 chronic kidney disease (CKD) who now has hyperphosphatemia should begin taking a phosphate binder such as sevelamer. Elevated serum phosphorus levels, particularly exceeding 6.5 mg/dL (2.09 mmol/L), are closely associated with increased mortality. Most patients with severe CKD require oral phosphate binders to be administered with meals. This patient also has known cardiovascular disease and vascular calcification. The Kidney Disease Improving Global Outcomes (KDIGO) guidelines suggest avoiding the use of calcium-containing phosphate binders in patients with known vascular calcification due to the potential for an increase in calcium absorption and worsening calcification of vessel walls. Therefore, a non-calcium–containing phosphate binder such as sevelamer or lanthanum is the preferred agent for this patient. Ferric citrate, another non-calcium–containing phosphorus binder, was recently approved for use in patients receiving dialysis but is not yet approved for patients with non-dialysis CKD.

Although this patient has secondary hyperparathyroidism, administration of calcitriol will increase intestinal absorption of calcium and phosphorus, which will exacerbate the hyperphosphatemia and potentially worsen vascular calcification.

Although administration of oral calcium carbonate will lead to increased absorption of calcium that may treat this patient's mild hypocalcemia and reduce her parathyroid hormone (PTH) levels, it may exacerbate vascular calcium in the setting of severe hyperphosphatemia.

Administration of the calcimimetic cinacalcet will likely decrease this patient's PTH level toward the normal range; however, it will worsen her hypocalcemia and is not an effective treatment for the hyperphosphatemia.