Angela M. Cheung, MD, PhD, FRCP(C), CCD, Director, Osteoporosis Program, University Health Network and Mount Sinai Hospital; Associate Director, Women’s Health Program, University Health Network; Associate Professor, University of Toronto, Toronto,ON.

Osteoporosis is common in postmenopausal women and older men. There are various efficacious therapies for the treatment of osteoporosis and the prevention of osteoporotic fractures in Canada. First-line therapies include alendronate, risedronate and raloxifene; all of these are oral antiresorptive therapies. In this article, we review new drug therapies currently or soon to be available in Canada, such as bone formation therapies (parathyroid hormone and strontium ranelate) and intravenous infusions (such as zoledronic acid), and compare them to existing therapies.
Key words: osteoporosis, osteoporotic fractures, parathyroid hormone, strontium, zoledronic acid.

The most effective bone-building treatment may turn out to be a modified form of parathyroid hormone. Researchers report that a peptide formed from the first 34 amino acids of parathyroid hormone is effective in preventing fractures in post-menopausal women. Previously, it was known that injections of parathyroid hormone, or its amino terminal fragment (parathyroid hormone 1-34), increased bone formation and bone mass, but their effects on fractures were unknown.

Women were randomly assigned to receive 20 or 40 mg of parathyroid hormone (1-34) or placebo, administered subcutaneously on a daily basis, for a period of 21 months. Vertebral radiographs and serial measurements of bone mass revealed that the risk of new vertebral fractures and non-vertebral fractures was decreased in the treatment groups; that increases were seen in vertebral, femoral and total-body mineral density; and that the drug is well-tolerated.

The study found that the 40-mg dose increased bone mineral density more than did the 20-mg dose but had similar effects on the risk of fracture and was more likely to have associated side effects.

The study was stopped early because another study on the same peptide fragment found that rats developed bone cancer when given life-long doses. However, researchers eventually decided that the results do not suggest a higher cancer risk in humans.

Source

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