The combination of two different osteoporosis drugs does not lead to any extra increase in bone density.

Sometimes 'less is more' as evidenced by a new study on osteoporosis in men. Researchers at Massachusetts General Hospital gave men with the condition both alendronate and parathyroid hormone (PTH). These two drugs are standard treatment for osteoporosis.

At the end of the three year study, men receiving both alendronate and PTH had lower bone density than those receiving PTH alone. Another study of this kind is underway in postmenopausal women. In the male study, combination therapy was found to increase bone density in the spine more than alendronate alone, but less than with PTH alone. Further research is now needed into the best way of using the available drugs for osteoporosis to increase bone density in those at risk.

Source

New England Journal of Medicine 25th September 2003