Comparison of subacute effects of oxazacort and prednisone on mineral metabolism in man.

Prolonged therapeutic administration of prednisone or other corticosteroids frequently produces severe osteopenia with an increased incidence of bone fractures. Recent efforts to decrease the severity of corticosteroid-induced osteopenia have included the development of corticosteroid analogues designed to possess diminished bone-wasting effects relative to their anti-inflammatory activity. We compared the effects of an oxazoline derivative of prednisolone, oxazacort (azacortinol), with those of prednisone on mineral metabolism in man. After a 12-day equilibration period on a 600 mg/day calcium diet, normal volunteers were studied for 15 days during treatment with either prednisone (20 mg/day, 12 subjects) or oxazacort (25 mg/day, 10 subjects). There was no difference between the two groups with regard to the effects of each corticosteroid on serum ionized calcium, phosphate, alkaline phosphatase, immunoreactive parathyroid hormone (iPTH), and 25-hydroxyvitamin D (25OHD) concentrations. Both corticosteroids suppressed intestinalCa absorption to a similar degree after 15 days of treatment (prednisone: −28.5±7.5, oxazacort: −30.2±4.4% of initial values). Although both corticosteroids increased 24-h urinary calcium excretion significantly above pretreatment values, this effect was less marked in the oxazacort-treated subjects. The mean cumulative 15-day increase in urinary calcium excretion in the prednisone-treated group (+326 ± 54 mg/g creatinine/24 h) was more than twice as great as that in the oxazacort-treated group (+146 ± 48 mg/g creatinine/24 h), a difference significant at P<0.001. It is concluded that the increase in urinary calcium excretion, and presumably the negative calcium balance, produced by a 2-week administration of oxazacort is significantly less pronounced than that produced by an equivalent dose of prednisone. [ABSTRACT FROM AUTHOR]