Drugs for the Treatment of Osteoporosis: Calcitonin and Bisphosphonates

In our article on osteoporosis medications, you can learn about all medications approved to treat osteoporosis. This article focuses on 2 of those: calcitonin and bisphosphonates.

Calcitonin

/osteoporosis

Calcitonin is a hormone which is naturally produced in the thyroid.  Calcitonin is a powerful inhibitor of osteoclastic activity (the cells which continuously reabsorb bone).

When given to patients with osteoporosis, calcitonin produces modest increases in bone mass.  Synthetic calcitonin is FDA-approved for the treatment of osteoporosis.

Patients with bones that are being destroyed quickly seem to do the best with this drug. The big disadvantage for this drug early on, however, was that it had to be given as an injection--it couldn't be given as a pill.

Remember, this drug is a man-made imitation of a real hormone, and taking this or any protein-based hormone orally will result in it being digested in the stomach and intestines prior to it being absorbed into the blood stream.

In response to this, the FDA approved a new formulation of calcitonin which allowed this powerful hormone to be sprayed into the nose. This was approved in 1991, and it allowed the medication to be very quickly absorbed into the blood stream.  Patients tolerate this very well since it is easy to take.   The skeletal effects of calcitonin may be slightly less than they are for estrogens or biophosphonates.  Some physicians have reported that calcitonin may decrease bone pain associated with osteoporotic fractures.

Biophosphonates

Biophosphonates constitute another category of drugs that are primarily anti-resorptive (that is, they prevent or significantly slow the normal osteoclastic activity responsible for the resorption of bone).

The mechanism by which these drugs slow the development of osteoporosis is not completely known.  The drugs appear to bind to the inner linings of bones preventing the osteoclasts from removing the bone. Some examples of medications in this category are alendronate and risedronate. 

AtheroscleosisIt is not clear that women can be on biophosphonates instead of estrogens.  Most endocrinologists suggest that women who can take estrogens should do so.  It should be remembered that estrogens also protect the cardiovascular system and decrease the risk of heart attack and stroke, in addition to maintaining bone density.  Women who cannot take estrogens (such as those with breast cancer), as well as men with osteoporosis may derive great benefit from this group of medications.