Intermittent oral disodium pamidronate in established osteoporosis: A 2 year double-masked placebo-controlled study of efficacy and safety

The effect of oral pamidronate on bone mineral density and its adverse effect profile was investigated by a double-masked placebo-controlled study of 122 patients aged 55-75 years with established vertebral osteoporosis. Patients on active therapy received disodium pamidronate 300 mg/day (group A) for 4 weeks every 16 weeks, 150 mg/day (group B) for 4 weeks every 8 weeks or placebo (group C). All patients additionally received 500 mg of calcium and 400 IU vitamin D daily. Dual-energy X-ray absorptiometry measurements of the spine, hip, forearm and total body were performed at baseline and 6-monthly for 2 years using a Hologic QDR 1000 device at two sites. Serum osteocalcin and urinary deoxypyridinoline were measured at the above visits and at 3 months. The percentage change (SEM) in spine bone mineral density (BMD) at 2 years based on intention-to-treat analysis was 4.64 (1.01) in group A, 6.10 (0.87) in group B and 1.13 (1.32) in group C. Analysis of variance showed significant increases in group A and B compared with placebo (p<0.01). There were also significant rises in femoral neck BMD for group A (p = 0.005), trochanter BMD for groups A and B (p<0.01) and total-body BMD for groups A and B (p<0.001). There was a significant reduction in serum osteocalcin and urinary deoxypyridinoline for groups A and B (p<0.01). There was an excess of gastrointestinal side-effects in the treated groups, particularly group A. We conclude that intermittent pamidronate therapy can prevent bone loss at both the lumbar spine and femoral neck in patients with established vertebral osteoporosis, although due to gastrointestinal side-effects the 300 mg dose in particular does not appear suitable for clinical usage.