The Newest Drugs for the Treatment of Osteoporosis

Calcitonin

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: see our page on this).  When given to patients with osteoporosis, calcitonin produces modest increases in bone mass.  Synthetic calcitonin is FDA approved for the treatment of osteoporosis. It is manufactured by Novartis under the trade name Miacalcin. 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...remember, many hormones are proteins and thus if we take them orally they become food!).  Recently, however, a new formulation has been developed which allows this powerful hormone to be sprayed into the nose were it is very quickly absorbed into the blood stream (this is Miacalcin).  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 new 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. The main drugs in this category are Alendronate (Fosamax) and Risedronate (Actonel).  In a recent study, Fosamax was given to post-menopausal women for 3 years and led to important gains in bone mineral density in the spine and hip.   Another large (and recent) study showed this drug to lead to a 50% reduction in fractures (including hip and spine) compared to women taking calcium only.

It 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 new group of drugs.  In fact, all women may have the potential for great benefit from this class of drugs...its a bit early to tell but it looks very promising.  There are a number of studies ongoing now to address the issue of combination therapies to see if a number of the above treatments could improve skeletal health to the point where osteoporosis fractures are rare.