Starting hemodialysis patients on a low dose of cinacalcet every other day is both safe and effective for secondary hyperparathyroidism (SHPT), a small study from Thailand suggests.
Over 16 weeks, similar proportions of patients in a standard-dose and low-dose group experienced the study’s primary outcome of a greater than 30% drop in intact parathyroid hormone levels (iPTH): 38.5% vs 33.3%.
The low-dose group included 16 patients who received 25 mg cinacalcet every other day for the first 8 weeks, with a possible dose increase to 25 mg daily if targets were not achieved. The standard-dose group included 14 patients who received 25 mg cinacalcet daily to start. Use of active vitamin D and its analogs or phosphate binders was permitted during the study and their dosages did not change.
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The groups also experienced similar reductions in iPTH. In the low-dose group, mean iPTH levels fell by 253.5 pg/mL from 1065.9 pg/mL at baseline. In the standard-dose group, mean iPTH levels dropped by 243.4 pg/mL from 1214.1 pg/mL.
“Among patients with secondary HPT, initial treatment with cinacalcet 25 mg on alternate days can decrease serum PTH levels,” Pongsathorn Gojaseni, MD, of Bhumibol Adulyadej Hospital in Bangkok, Thailand, and colleagues wrote in the International Journal of Nephrology and Renovascular Disease. “The role of low-dose cinacalcet in secondary HPT should be further determined in large-scale, randomized controlled trials.”
More patients in the low-dose group reported gastrointestinal (GI) side effects (43.8% vs 7.1%). One patient in the standard-dose group with a dose increase to 50 mg daily experienced a serious GI problem that led to medication discontinuation. Hypocalcemia occurred in 18.8% and 28.6% of low-dose and standard-dose patients, respectively; no patient had pre-existing hypocalcemia. Numbness developed in 7.1% of standard-dose patients.
Cinacalcet modulates the calcium-sensing receptor in the parathyroid glands. Although it has a long-elimination half-life (more than 30 hours), its pharmacokinetic profile does not fully explain the results, according to the investigators. Data from Western populations show that approximately 40% of patients can be maintained on 25 mg cinacalcet daily, they noted.
Patients in the low-dose group tended to be younger and have higher serum phosphate levels and better nutritional status, which may have affected the results.
