Prolia for Osteoporosis

Dr. Landis, December 2018

Osteoporosis is a disease where increased bone weakness increases the risk of bone fracture. Bones weaken to such a degree that a break may occur with minor stress or a break may even occur spontaneously. Bones that commonly break include the vertebrae in the spine, the bones of the forearm, and the hip. Until a broken bone occurs, there are typically no symptoms.

Hip fractures lead to decreased mobility and other complications like fatal blood clots and pneumonia. The six-month mortality rate following hip fracture is around 13.5% and the twelve-month mortality rate is around 20-30%. A year after fracturing a hip, 90 percent of those who needed no assistance climbing stairs before the fracture will not be able to climb five stairs. 66 percent won't be able to get on or off a toilet without help. 50 percent won't be able to raise themselves from a chair. 31 percent won't be able to get out of bed unassisted. 20 percent won't be able to put on a pair of pants by themselves.

Vertebral fractures, while having a lesser impact on mortality rates, can lead to severe chronic pain from nerve compression and may lead to deformity of the spine. Multiple vertebral fractures may lead to such a severe hunch back that the resulting pressure on internal organs can impair one's ability to breathe.

The U.S. Preventive Services Task Force recommends that all women 65 years of age or older be screened for osteoporosis. A DEXA scan is considered the gold standard for the diagnosis of osteoporosis. Osteoporosis is diagnosed when the T-score is less than or equal to "-2.5". The need to treat the osteoporosis is based on a FRAX score. This score is calculated based upon risk factors, age, sex, weight, height, race, and bone mineral density. To reduce risk of fracture, the current National Osteoporosis Foundation Guide recommends treating patients with FRAX 10-year risk scores of "> or = 3%" for hip fracture or "> or = 20%" for major osteoporotic fracture.

Osteoporosis treatment usually begins with an oral bisphosphonate, but this may not be well tolerated due to severe reflux or declining T-scores as a result of poor gastrointestinal absorption. Bisphosphonates are contraindicated in renal disease. Prolia, a subcutaneous injection that is administered every 6 months at the doctor's office, is a viable alternative to bisphosphonates and may be used in certain degrees of renal failure.

Prolia works differently than the bisphosphonates. By inhibiting a molecule called RANKL, the antibody Prolia prevents the development of osteoclasts that break down bone. This action leads to a 70% relative risk reduction in vertebral spine fractures and a 40% relative risk reduction in hip fractures over the course of 3 years.

Side effects of Prolia may include a low calcium level, serious infection, rash, osteonecrosis of the jaw, and decreased bone turnover. Prolia is contraindicated in pregnancy and while breast feeding.