Using Cinacalcet to Treat the Hypophosphatemia of Early Kidney Transplant

Secondary hyperparathyroidism (SHPT), common in ESRD, persists following renal
transplantation resulting in profound hypophosphatemia. This can lead to hemolysis,
congestive heart failure, rhabdomyolysis. Phosphate repletion is difficult in view of the
persistent SHPT: oral phosphate supplementation can lead to hypocalcemia, reduced 1,25-OH
Vitamin D production, hypercalcemia and further hyperparathyroidism. In addition,
phospho-soda has been associated with phosphate nephropathy and renal failure.

Cinacalcet HCl is a calcimimetic agent that has recently become a standard therapy in the
treatment of SHPT in ESRD. It suppresses PTH secretion by acting as a modulator of the
Calcium-sensing receptor on the PTH cell, causing the PTH cell to decrease production of
parathyroid hormone. It is a very effective agent, producing significant reduction of PTH as
well as improvement in calcium and phosphate metabolism in the dialysis patient. The drug is
well-tolerated with minimal adverse effects. Cinacalcet has also been used to control
hypercalcemia in renal transplant patients with persistent hyperparathyroidism. Short-term
cinacalcet given for 2 to 4 weeks has normalized serum phosphorus and decreased urinary
phosphate wasting in renal transplant recipients with stable graft function.

We hypothesize that Cinacalcet HCl will normalize the hypophosphatemia of early renal
transplant by reducing the effects of PTH on the proximal renal tubular transport of
phosphorus, thereby allowing phosphate reabsorption and decreasing urinary phosphate
wasting.

Inclusion Criteria:

- renal transplant within last 3 months

- serum phosphorus less than 2.0 mg/dl

- serum creatinine less than 2.0 mg/dl

Exclusion Criteria:

- sensitivity to cinacalcet

- use of amitryptiline, desipramine, itraconazole, ketoconazole

- pregnancy