Combined calcitriol-pamidronate therapy for bone hyperresorption in spinal cord injury

Objective: To determine the biochemical effects of combined calcitriol-pamidronate therapy on bone hyperresorption in patients with spinal cord injury (SCI). Methods: This was a retrospective study of 21 SCI inpatients (4 women and 17 men, mean age 34 years) treated for bone hyperresorption. Initial treatment was 0.5 μg oral calcitriol once daily and 1250 mg CaCO ₃ twice a day (1000 mg elemental calcium/day). On days 4 through 6 following the initial treatment, patients received 30 mg pamidronate intravenously once daily (total of 3 doses). Urinary N-telopeptide (NTx) and calcium excretion rates, and serum parathyroid hormone (PTH), 25-hydroxyvitamin D (25-D), 1,25-dihydroxyvitamin D (1,25-D), calcium, and phosphorus levels were measured within 2 weeks prior to and 2 weeks following pamidronate therapy. Results: Patients demonstrated increased urinary NTx and calcium excretion, indicative of bone hyperresorption, and suppressed PTH and 1,25-D levels as early as 9 days post-SCI. Combined calcitriol-pamidronate therapy decreased urinary NTx and calcium excretion by 71% (P < .001) and 73% (P < .001), respectively. This therapy also increased serum levels of PTH (P < .05) and 1,25-D (P < .005). Post-pamidronate hypocalcemia or hypophosphatemia was observed in 44% (P < .01) or 53% (P < .01), respectively. Conclusion: Combined calcitriol-pamidronate therapy significantly inhibited bone hyperresorption in SCI patients.