It’s always great when new uses are discovered for drugs that are already on the market, and such is the case with the osteoporosis drug Forteo (teriparatide), which is a recombinant form of parathyroid hormone.

It’s been discovered by researchers at the University of Rochester Medical Center (and reported here) that teriparatide boosts bone stem cell production to the point that adults’ bones heal at a much faster rate, similar to that of young children.

While this is likely to be of benefit to anyone with a fracture, it’s particularly useful for those with fractures that remain chronically unhealed. Teriparatide kick starts the process, and in a study of 145 patients with these kinds of recalcitrant breaks, 93% experienced marked healing and relief from pain in 8 to 12 weeks.

The clinical implication is significant, as orthopaedists can soon have a new tool at their disposable to deal with many common, painful bone ailments including the tens of thousands of painful fractures for which there is no treatment (pelvic fractures, vertebral compression fractures, clavicle fractures), fractures that won’t heal, fractures in patients that are either too sick to have surgery or chose not to have surgery, and even reduce the size of a incision in some surgeries.

While those of us averse to needles will be disappointed to learn that teriparatide is administered daily by (although reportedly painless) injection, the fact that this is a real drug, in production, approved, and available now is a refreshing change from most discoveries, which have to sit under the Christmas tree for the next 10 years.

When a fracture occurs, a bone becomes unstable and can move back and forth creating a painful phenomenon known as micromotion. As the bone begins healing it must progress through specific, well-defined stages. First, osteoclasts – cells that can break down bone – clean up any fragments or debris produced during the break. Next, a layer of cartilage – called a callus – forms around the fracture that ultimately calcifies, preventing the bony ends from moving, providing relief from the significant pain brought on by micromotion.
Only after the callus is calcified do the bone forming cells – osteoblasts – begin their work. They replace the cartilage with true bone, and eventually reform the fracture to match the shape and structure of the bone into what it was before the break.

Teriparatide speeds this process by speeding up the formation of the callus and stimulating the osteoblasts, the cells that produce bone, to produce more bone and faster. The completion of the formation of the callus is the milestone at which point the pain of the injury is markedly diminished as it stops the micromovement of the fracture that generates the pain.

All in all, teriparatide more than halved the normal healing time for the patients.

Photo credit: KooshKing on Flickr