Calcitonins: Newer Routes of Delivery

Because of its anti-osteoclastic and analgesic properties, calcitonin is a first-line choice in the treatment of several bone diseases characterized by absolute or relative bone resorption. With regard to the prevention and treatment of postmenopausal osteoporosis, the chronic nature of the disease and the subsequent long duration of the pharmacological intervention require uncomfortable parenteral administration to be repeated on a long-term basis. Newer routes of administration have therefore been developed. At present the most promising of these are the nasal spray and the rectal suppository. Both routes have been shown to induce significant increases in plasma levels of salmon calcitonin. The ability of salmon calcitonin to cross the nasal mucosa was shown immunologically by the generation of specific anti-salmon-calcitonin antibodies in the plasma. In healthy volunteers these alternative routes of administration do not decrease the anti-osteoclastic activity of calcitonin, as demonstrated by a significant decrease in biochemical parameters that reflect bone turnover. In the prevention and treatment of postmenopausal osteoporosis, as well as in the treatment of Paget's disease of bone, the properties of calcitonins are generally preserved if they are administered non-parenterally. However, the equivalent doses required to sustain the effects of calcitonin have not been fully elucidated. This article reviews the potential benefits of two methods of non-parenteral administration of calcitonins in the prevention and treatment of postmenopausal osteoporosis.