The Effect of the Concomitant Administration of Active Vitamin D on the Safety of Once-a-Day Subcutaneous Injection of Teriparatide 20 μg/day

Abstract

Vitamin D plays an important role in bone metabolism by controlling calcium absorption in the small intestine. In Japan, active vitamin D drugs are approved for treatment of osteoporosis. Studies of teriparatide and active vitamin D coadministration are limited, and none pertain to the Japanese population. This study assessed teriparatide and active vitamin D coadministration for 28 days in a Japanese population by assessing changes in serum and urinary calcium. Subjects were to be Japanese males or postmenopausal females with osteoporosis, who were ≥55 years of age residing in Japan. Of the 30 female subjects who entered the study, 29 subjects received at least one dose of teriparatide, and 28 subjects completed the study. The study included screening, 14-day lead-in, 28-day cotreatment, and 7-day follow-up periods. Upon entering the lead-in period, subjects were administered daily, oral, active vitamin D (alfacalcidol [Alfarol^®] 1.0 μg/day) and calcium supplements; teriparatide (20 μg/day) coadministration began during the cotreatment period. There were no reports of hypercalcemia or hypercalciuria. No subjects had corrected serum calcium concentrations ≥11.0 mg/dL at 16 or 24 hours postdose during the cotreatment period or any time during the study. The highest observed serum calcium was 10.3 mg/dL at 4 hours postdose. Serum calcium concentrations (corrected and total) increased at 2, 4, and 6 hours, and returned to baseline levels at 16 and 24 hours postdose. No subject had a daily urinary calcium excretion above 0.3 g/day at any time. Findings were similar to previous studies that assessed teriparatide and native vitamin D coadministration. The risks associated with coadministration of teriparatide and active vitamin D seemed low, and there were no additional risks indicated other than those seen with native vitamin D. However, since these were findings from a clinical trial, further experience in actual clinical practice will be needed.
(Jpn J Clin Pharmacol Ther 2013; 44(5): 395-403)