Low-dose calcitriol versus calcium in established postmenopausal osteoporosis.

An ongoing randomized clinical trial of 3 years duration is being undertaken to evaluate the recurrent fracture rate and safety profile associated with low-dose calcitriol versus calcium supplementation in women with at least 3 years postmenopausal osteoporosis who are under the age of 80 years. A total of 856 patients were submitted for possible inclusion in the study by 123 primary care physicians, and 636 met all entry requirements. Each patient was randomly allocated to receive either 0.25 micrograms of calcitriol twice daily or calcium supplementation of 1,000 mg/d. If significant hypercalcemia developed (greater than 2.6 mmol/L) or a deterioration in renal function was observed, the dose of trial medication was to be halved or stopped if laboratory values did not return to normal. Patients were given no specific instructions regarding dietary calcium intake. To date, 528 patient-years experience with calcitriol and 527 patient-years experience with calcium the calcium supplementation have been accumulated. Thus far, low-dose calcitriol has not been observed to cause hypercalcemia, deterioration in renal function, or nephrocalcinosis. At 1 year, a loss in total anterior height (P less than .05) has been detected in the calcium-treated group compared with the calcitriol-treated group. Thus, calcitriol appears to preserve spinal height. Long-term follow-up of all patients for 2 or 3 years will be continued.