In Vivo Calcium and Phosphate Iontophoresis for the Topical Treatment of Osteoporosis

Abstract

In addition to systemic treatment, osteoporosis may be treated topically by incorporating calcium and phosphate into the bone. This article describes the use of a recently developed, novel iontophoretic apparatus suitable for local ion delivery into bones. In this study, in vivo experiments were performed to compare the effects of local electrotherapy and those of systemic hormone replacement on bone. In this study, local iontophoresis was carried out in ovariectomized and control rats. Bone density, biomechanical, and elemental studies were performed. Forty 12-week-old Sprague-Dawley rats received an ovariectomy (OVX) or were sham-operated (sham). Twenty-one weeks later, tibias of subgroups of sham-operated and OVX animals were subjected to serial local iontophoresis (IOP) treatments, received systemic subcutaneous 17β-estradiol (E2), or were treated with the combination of IOP and E2. Changes in bone density were detected by quantitative ultrasound densitometry and expressed as amplitude-dependent speed of sound (AD-SoS). Biomechanical studies and elemental analysis were performed at the end of the experiments. Osteopenia developed 21 weeks after OVX in the proximal tibial regions; the mean difference estimate (95% confidence intervals) of AD-SoS values between the sham-operated and OVX animals was 188.7 (140.4-237.1). Serial iontophoretic treatment resulted in an increase in bone density in both sham-operated and OVX animals (sham+IOP versus sham: 121.4 [73.01-169.7]; OVX+IOP versus OVX: 241.6 [193.2-289.9]). Similar changes in AD-SoS were detected after 17β-estradiol (E2) treatment; however, even greater changes occurred after OVX+E2+IOP versus OVX+E2 (123.4 [75.1-171.8]). Similar improvements also were evident regarding the biomechanical features of the tibias. A limitation of this study was the relatively small number of rats. The efficacy of local IOP using calcium- and phosphate-donating microparticles is comparable to that of estrogen therapy as evidenced by steadily increasing bone density, restoration of the calcium and phosphate balance, and improvement in the biomechanical properties of the bone.