The effect of 1 alpha-hydroxyvitamin D3 on the mineralization defect in disodium etidronate-treated Paget's disease--a double-blind randomized clinical study.

A double-blind randomized study of 29 patients with symptomatic Paget's disease was conducted comparing the clinical, biochemical, and histomorphometric responses to 3-month treatment with placebo (10 patients), low-dose disodium etidronate (EHDP) (5-7 mg/kg/day) (10 patients), and low-dose EHDP plus 1 alpha-hydroxyvitamin D3 (1 alpha D3) 0.5 mcg daily (9 patients). In placebo-treated patients no significant changes were observed in symptoms, biochemistry, or bone histomorphometry. Histologically apparent mineralization defects developed after 3 months of therapy in 90% of patients in the EHDP group, compared with 45% of patients in the EHDP/1 alpha D3 group. In 19% of the patients treated with active medication, the mineralization defects in pagetic bone were accompanied by histological evidence of continued osteoclastic resorption. The development of mineralization defects was not related to serum levels of vitamin D metabolites, alkaline phosphatase, or intestinal calcium absorption but did correlate with the occurrence of hyperphosphatemia during treatment, which was most marked in patients treated with EHDP alone. Although mineralization defects were less frequent in the EHDP/1 alpha D3 group, these patients also responded less well symptomatically, thus limiting the potential usefulness of this drug combination in Paget's disease.(ABSTRACT TRUNCATED AT 250 WORDS)