Analgesic effect of calcitonin in osteoporosis.

Bone pain is the most common symptom in osteoporotic patients. To date, there is mounting evidence that calcitonin significantly reduces bone pain in osteoporosis, and that the analgesic effect can be evident as soon as the second week of treatment. The limitations to the use of calcitonin, which are parenteral administration and side effects, can now be overcome by the availability of the nasal spray preparation. At present, controlled studies have demonstrated the analgesic activity of calcitonin given by nasal spray in patients with vertebral crush fractures and bone pain. The mechanism for the analgesic effect of calcitonin is yet to be clarified. In humans, similarities between calcitonin and morphine-induced analgesia, and reports of calcitonin-induced elevation of plasma beta-endorphin levels, suggest the possible involvement of the endogenous opiate system in mediating the analgesic action of calcitonin. However, the demonstration of calcitonin binding sites in areas of the brain involved in pain perception and a series of animal studies have raised the possibility that calcitonin may directly modulate nociception in the central nervous system. In support of this hypothesis are some observations of an analgesic effect obtained by direct epidural or subaracnoidal injection of calcitonin in humans.