Comparative response in growth and bone status to three dexamethasone treatment regimens in infant piglets

The objectives of this study were 1) to determine whether a zenith in bone formation (indicated by circulating osteocalcin) existed at night in early life, and 2) to compare the effects of three different dexamethasone (DEX) treatment regimens on bone turnover, bone mineral content, and growth. Thre e DEX treatment regimens were tested in 8-d-old piglets (n = 8/group): I) l ow evening dose of DEX (0.5 mg/kg/d) as 70% in the morning and 30% in the e vening for 10 d; 2) tapering course of DEX (0.5, 0.3, and 0.2 mg/kg/d) as 5 0% in the morning and 50% in the evening for 14 d; and 3) constant dose of DEX (0.5 mg/kg/d) as 50% in the morning and 50% in the evening for 10 d. Or al water placebo groups were tested with the same time courses. At pretreat ment, plasma osteocalcin was significantly higher (p < 0.05) at 0100 than a t 0900 and 1700. At necropsy, measures for DEX groups were calculated as Z- scores using values from the placebo groups. The low evening DEX dose led t o a significantly lower reduction in plasma osteocalcin compared with the t apered and constant dosing regimens (p < 0.05). The significant weight redu ction in the DEX group occurred at d 3 in the low evening dose regimen but at d 7 in the constant dosing regimen, compared with the placebo group. Bon e mineral content Z-score was reduced similarly in all DEX-treated groups a cross the three dosing regimens. We conclude that a plasma osteocalcin zeni th at night exists in early life. A high DEX dose in the morning and low DE X dose in the evening may partially attenuate corticosteroid-induced suppre ssion of bone formation and growth restriction.