Bone Abstracts

Ibandronate (IBN), a nitrogen-containing bisphosphonate, and eldecalcitol (ELD), an active vitamin D₃ derivative, are used for osteoporosis treatment. Vitamin D₃ often used in combination therapies, however, there are no reports on the effects of combined IBN and ELD treatment for osteoporosis.

In this study, we examined the effects of combination treatment with IBN and ELD in aged ovariectomized rats. Eight-month-old Wistar-Imamichi rats were ovariectomized and treated for 12 weeks with either vehicle, IBN (3 μg/kg per month, S.C., monthly), ELD (15 ng/kg per day, p.o., daily), or a combination of IBN and ELD.

Urinary DPD was reduced in each monotherapy group. The combination treatment showed further decreases in DPD compared to each monotherapy group. Osteocalcin in all therapy groups was not lower than the level in the sham group.

Lumbar BMD was higher in the monotherapy groups than in the vehicle control group, and was higher in the combination group than in both monotherapy groups. A mechanical strength of lumbar was improved in monotherapy groups and in the combination group. The maximum load was higher in the combination group than in the IBN monotherapy group.

In femurs, BMD was increased in both monotherapy groups, and was higher in the combination therapy group than in both monotherapy groups. The maximum load of femurs was higher in the combination group than in the vehicle control group.

Bone histomorphometry analysis revealed that combination therapy result in additive effects on reduction of ES/BS in cancellous and endosteal cortical bone in femurs, but bone formation parameters such as MS/BS or BFR/BS were not less than Sham level.

This study suggests the additive effects of IBN and ELD combination therapy on the mechanical strengths of the lumbar vertebrae and femur. These effects may be induced by increased BMD via reduction of bone resorption without severe suppression of bone formation.