Combination/sequential therapy in osteoporosis.
Combination therapy includes the concomitant or sequential use of compounds sharing the same mode of action (eg, two or more inhibitors of bone resorption) or with distinct pathways of activity (eg, an inhibitor of resorption plus an anabolic agent). Combination use of antiresorptive agents may generate concerns, because of the risk of inducing oversuppression of bone turnover. However, if low doses of estrogen, used for the management of climacteric symptoms, are insufficient to normalize bone turnover, the addition of a bisphosphonate to hormone therapy may prove to be useful to achieve this objective. Patients pretreated with inhibitors of resorption, who have not achieved a full therapeutic response, are good candidates for treatment with anabolic agents. The increase in bone turnover that comes after the introduction of parathyroid hormone (PTH) in patients treated with an antiresorptive agent is similar to that observed in treatment-naïve patients and the pattern of bone mineral density (BMD) increase is also identical, with the exception of a 6 month delay in the spine and hip BMD changes observed in prior alendronate-treated subjects. Current data discourage the concomitant use of alendronate and PTH since the bisphosphonate appears to blunt (in men and women) the anabolic action of PTH. Whether this applies to other bisphosphonates or inhibitors of resorption, remains unknown. The use of an inhibitor of bone resorption after completion of PTH treatment seems an appropriate way to maintain the skeletal benefits gained during therapy. Long-term clinical studies, using fractures as an endpoint should be initiated to better understand the clinical and pharmaco-economic interest of combination therapies in the management of osteoporosis.