Bone Mineral Density

Two 1-year, double-blind, placebo-controlled trials in patients who were taking greater than or equal to 7.5 mg/day of prednisone or equivalent demonstrated that risedronate sodium tablets 5 mg daily was effective in the prevention and treatment of glucocorticoid-induced osteoporosis in men and women who were either initiating or continuing glucocorticoid therapy. The efficacy of risedronate sodium tablets therapy for glucocorticoid-induced osteoporosis beyond one year has not been studied.

The prevention study enrolled 228 patients (risedronate sodium tablets 5 mg, N = 76) (18 to 85 years of age), each of whom had initiated glucocorticoid therapy (mean daily dose of prednisone 21 mg) within the previous 3 months (mean duration of use prior to study 1.8 months) for rheumatic, skin, and pulmonary diseases. The mean lumbar spine BMD was normal at baseline (average T-score - 0.7). All patients in this study received supplemental calcium 500 mg/day. By the third month of treatment, and continuing through the year-long treatment, the placebo group experienced losses in BMD at the lumbar spine, femoral neck, and trochanter, while BMD was maintained or increased in the risedronate sodium tablets 5 mg group. At each skeletal site there were statistically significant differences between the placebo group and the risedronate sodium tablets 5 mg group at all timepoints (Months 3, 6, 9, and 12). The treatment differences increased with continued treatment. Although BMD increased at the distal radius in the risedronate sodium tablets 5 mg group compared to the placebo group, the difference was not statistically significant. The differences between placebo and risedronate sodium tablets 5 mg after 1 year were 3.8% at the lumbar spine, 4.1% at the femoral neck, and 4.6% at the trochanter, as shown in Figure 3. The results at these skeletal sites were similar to the overall results when the subgroups of men and postmenopausal women, but not premenopausal women, were analyzed separately. Risedronate sodium was effective at the lumbar spine, femoral neck, and trochanter regardless of age (less than 65 vs. greater than or equal to 65), gender, prior and concomitant glucocorticoid dose, or baseline BMD. Positive treatment effects were also observed in patients taking glucocorticoids for a broad range of rheumatologic disorders, the most common of which were rheumatoid arthritis, temporal arteritis, and polymyalgia rheumatica. 

The treatment study of similar design enrolled 290 patients (risedronate sodium tablets 5 mg, N = 100) (19 to 85 years of age) with continuing, long-term (greater than or equal to 6 months) use of glucocorticoids (mean duration of use prior to study 60 months; mean daily dose of prednisone 15 mg) for rheumatic, skin, and pulmonary diseases. The baseline mean lumbar spine BMD was low (1.63 SD below the young healthy population mean), with 28% of the patients more than 2.5 SD below the mean. All patients in this study received supplemental calcium 1000 mg/day and vitamin D 400 international units/day. 

After 1 year of treatment, the BMD of the placebo group was within 1% of baseline levels at the lumbar spine, femoral neck, and trochanter. Risedronate sodium tablets 5 mg increased BMD at the lumbar spine (2.9%), femoral neck (1.8%), and trochanter (2.4%). The differences between risedronate sodium tablets and placebo were 2.7% at the lumbar spine, 1.9% at the femoral neck, and 1.6% at the trochanter as shown in Figure 4. The differences were statistically significant for the lumbar spine and femoral neck, but not at the femoral trochanter. Risedronate sodium tablets were similarly effective on lumbar spine BMD regardless of age (less than 65 vs. greater than or equal to 65), gender, or pre-study glucocorticoid dose. Positive treatment effects were also observed in patients taking glucocorticoids for a broad range of rheumatologic disorders, the most common of which were rheumatoid arthritis, temporal arteritis, and polymyalgia rheumatica.

Figure 3 Change in BMD from Baseline Patients Recently Initiating Glucocorticoid Therapy

Figure 4 Change in BMD from Baseline Patients on Long-Term Glucocorticoid Therapy

Vertebral Fractures

In the prevention study of patients initiating glucocorticoids, the incidence of vertebral fractures at 1 year was reduced from 17% in the placebo group to 6% in the risedronate sodium tablets group. In the treatment study of patients continuing glucocorticoids, the incidence of vertebral fractures was reduced from 15% in the placebo group to 5% in the risedronate sodium tablets group (Figure 5). The statistically significant reduction in vertebral fracture incidence in the analysis of the combined studies corresponded to an absolute risk reduction of 11% and a relative risk reduction of 70%. All vertebral fractures were diagnosed radiographically; some of these fractures also were associated with symptoms (that is, clinical fractures).

Figure 5 Incidence of Vertebral Fractures in Patients Initiating or Continuing Glucocorticoid Therapy

Histology/Histomorphometry

Bone biopsies from 40 patients on glucocorticoid therapy were obtained at endpoint. Patients had received placebo or daily risedronate sodium tablets (2.5 mg or 5 mg) for 1 year. Histologic evaluation (N = 33) showed that bone formed during treatment with risedronate sodium tablets was of normal lamellar structure and normal mineralization, with no bone or marrow abnormalities observed. The histomorphometric parameter mineralizing surface, a measure of bone turnover, was assessed based upon baseline and post-treatment biopsy samples from 10 patients treated with risedronate sodium tablets 5 mg. Mineralizing surface decreased 24% (median percent change) in these patients. Only a small number of placebo-treated patients had both baseline and post-treatment biopsy samples, precluding a meaningful quantitative assessment.