Long-term treatment of established osteoporosis with intranasal calcitonin

We examined the long-term effects of intranasal administration of salmon calcitonin on bone and calcium metabolism in women with established osteoporosis (forearm fracture). Over a period of 5 years, 14 women received discontinuous calcitonin (200 IU) plus calcium (500 mg) daily for 3 years or 4 years. To allow assessment of the optimum duration of therapy, patients in whom treatment had been for shorter intervals were also included. At the end of the first 2 years, a group receiving placebo had lost significantly more bone from their spines and forearms than the group receiving calcitonin in the first year (P less than 0.01). In the 14 women who completed a further 3 years on calcitonin, the bone mineral contents of the spines increased continually. Bone loss in the forearm was arrested for 1 year. Treatment lasting for about 2 years prevented bone loss in both areas. Treatment for 3 years resulted in net gains in spinal bone but no further benefits in relation to forearms. Biochemical parameters of bone turnover (serum alkaline phosphatase levels, plasma bone Gla protein levels, and fasting urinary hydroxyproline/creatinine levels) exhibited similar declines irrespective of the duration of treatment. It is concluded that long-term intranasal treatment with calcitonin produced net gains in spinal bone and that optimum response in forearms was achieved using discontinuous therapy. The ratio between periods with and without treatment was between 1:2 and 2:3.