A study of maintenance therapy after intravenous maxacalcitol for secondary hyperparathyroidism

Intravenous vitamin D therapy is an established treatment for secondary hyperparathyroidism (SHPT). However, no protocols have been established for maintenance therapy with intravenous or oral vitamin D after control of intact parathyroid hormone (iPTH) within the target range.

Step I. For patients with SHPT (200 ≤ iPTH ≤ 500 pg/ml), a dose of 2.5 mg maxacalcitol (OCT) was administered intravenously three times a week with oral sevelamer hydrochloride; the dose was increased to a 10 µg maximum three times a week to control iPTH to < 150 pg/ml. Step II. When iPTH reached the target level, patients were assigned to Group A (oral alfacalcidol 1.0 µg/day) or B (oral alfacalcidol 0.25 µg/ day). Serum iPTH, calcium, and inorganic phosphorus were measured each month for 6 months. Maintenance rates for the target iPTH levels were evaluated, < 150 pg/ml at Step I and < 200 pg/ml at Step II.

iPTH decreased to < 150 pg/ml by OCT in 24 of 35 patients (68.6%). During the 24-week observation period, iPTH was controlled for 83.3% patients in Group A vs. 36.4% for Group B (p < 0.05). No dropouts due to hypercalcemia or hyperphosphatemia occurred.

OCT dose titration was effective for SHPT. A higher daily dose of oral alfacalcidol (1.0 µg) appears to be more effective than a lower dose (0.25 µg) as maintenance therapy after iPTH control.